Running Shoe Measurements Hub
Every running shoe spec sheet is a list of numbers, and once you can read them you can tell how a shoe will feel before you put it on. This hub explains the three groups that matter: the stack and geometry under your foot, the key dimensions like weight and width, and the performance ratings for cushioning, flexibility and stability. Learn what each number means and you can match a shoe to your stride without guesswork.
Stack & geometry
Stack Height
What is stack height?
Stack height is the distance from the ground to the top of the footbed where your foot sits, measured in millimetres. It is essentially how much shoe is underneath you. A maximal shoe might stack 40mm or more of foam, while a minimal racing flat can sit at 15mm or less.
Why it matters
Stack height shapes the whole feel of a run. More stack means more material to absorb impact, which protects legs over long distances, but it also raises you further from the ground and can feel less stable. Lower stack gives a firmer, more grounded, more responsive ride.
How it works
Brands usually quote stack at the heel and at the forefoot. The difference between those two numbers is the heel drop. Two shoes can share the same drop but feel completely different because one is built on a tall stack and the other on a thin one.
What to look for
Match stack to your running. High stack suits long, slow miles and recovery runs where cushioning matters most. Lower stack suits fast, short efforts and runners who want ground feel and stability. Many runners keep one of each for different sessions.
Common questions
What is a good stack height?
There is no single best number. 30 to 40mm suits cushioned daily runs, under 25mm suits fast, grounded shoes.
Is higher stack height better?
Not always. It cushions more but can feel less stable and less responsive. The right stack depends on the run.
Does stack height affect drop?
Drop is the difference between heel stack and forefoot stack, so the two numbers are directly related.
Is there a legal limit on stack height?
Yes, for elite road racing World Athletics caps it at 40mm, but everyday training shoes have no limit.
Does more stack mean more weight?
Often, since there is more foam, though modern lightweight foams keep many high-stack shoes surprisingly light.
Heel Stack
What is heel stack?
Heel stack is the measured height of foam and material beneath your heel, from the ground up to where the heel of your foot rests. It is one half of the stack picture, the other being the forefoot, and it is usually the taller of the two on a traditional running shoe.
Why it matters
The heel takes the first big impact for runners who land heel-first, so heel stack directly affects how that landing feels. A taller heel stack softens the strike and protects the legs; a lower one gives a firmer, more direct contact with the ground.
How it works
Heel stack is measured at the centre of the heel. Subtract the forefoot stack from it and you get the drop. This is why a shoe can have a generous overall cushion but still feel low at the front if the foam is concentrated under the heel.
What to look for
Heel strikers and runners covering long distances often prefer a taller heel stack for impact protection. Midfoot and forefoot strikers may prefer a lower, more even profile. Always read heel stack alongside forefoot stack rather than on its own.
Common questions
What does heel stack tell me?
How much cushioning sits under your heel, which sets impact protection at the rear of the shoe.
How is heel stack different from stack height?
Stack height usually refers to the heel measurement, but precisely it is the heel and forefoot stacks together.
Does heel stack set the drop?
Partly. Drop is heel stack minus forefoot stack, so heel stack is one of the two numbers involved.
Do heel strikers need a high heel stack?
Many find it more comfortable, since it cushions the first impact, but stride and preference vary.
Can heel stack be too high?
For some runners a very tall heel can feel unstable or encourage harder heel landing, so balance matters.
Forefoot Stack
What is forefoot stack?
Forefoot stack is the measured height of foam under the front of the shoe, where the ball of your foot pushes off. It is the partner measurement to heel stack, and on most shoes it is lower than the heel, creating the familiar downhill slope from back to front.
Why it matters
The forefoot is where you push off, so its stack affects how responsive and protected toe-off feels. More forefoot foam cushions the push and suits long runs; less foam gives sharper ground feel and a snappier, more direct transfer of power for faster running.
How it works
Forefoot stack is measured at the ball of the foot. The heel stack minus the forefoot stack gives the drop, so a shoe with a high forefoot stack and high heel stack can still be low drop if the two are close together.
What to look for
Forefoot and midfoot strikers feel forefoot stack most directly. If you want protection on long efforts, look for a generous forefoot; if you want speed and feel, a thinner forefoot transmits the ground more clearly. Read it together with the heel number.
Common questions
What does forefoot stack affect?
Cushioning and ground feel at toe-off, where the ball of your foot pushes off the ground.
Why is forefoot stack usually lower than heel stack?
Because most shoes have a positive drop, sloping down from a taller heel to a lower forefoot.
Do forefoot strikers need more forefoot stack?
They feel it most, so it is a matter of preference between protection and ground feel.
Does forefoot stack change the drop?
Yes, drop is heel stack minus forefoot stack, so raising the forefoot lowers the drop.
Is a high forefoot stack good for racing?
It can cushion long races, but some racers prefer a firmer, lower forefoot for sharper push-off.
Heel Drop
What is heel drop?
Heel drop, also called the offset, is how much higher the heel sits than the forefoot inside a running shoe. If the heel stack is 30mm and the forefoot is 22mm, the drop is 8mm. It is one of the most quoted numbers on a shoe's spec sheet.
Why it matters
Drop influences where your foot tends to land and how load is shared between the calf, Achilles and knee. Higher drops, around 10 to 12mm, shift load forward and suit heel strikers. Lower drops, 0 to 6mm, encourage a flatter landing and load the calf and Achilles more.
How it works
Drop is purely the difference between two stack numbers, so it says nothing about total cushioning. A thick, soft shoe and a thin, firm shoe can share the same drop. That is why drop should always be read alongside stack height rather than on its own.
What to look for
If you are comfortable in your current shoes, note their drop and stay in a similar range. Switching to a much lower drop loads the calf and Achilles more and should be done gradually. There is no single correct drop, only what suits your stride.
Common questions
What is a normal heel drop?
Traditional running shoes sit around 8 to 12mm, low-drop shoes at 0 to 6mm, with plenty in between.
Is a lower drop better?
Not inherently. It changes how load is shared, so the best drop depends on your stride and history.
Does drop tell me how cushioned a shoe is?
No. Drop is only the heel-to-forefoot difference. Stack height tells you the cushioning.
Can I switch to a lower drop?
Yes, but do it gradually, as a lower drop loads the calf and Achilles more than you may be used to.
Is heel drop the same as offset?
Yes, the two terms mean the same heel-to-toe height difference.
Offset
What is offset?
Offset is simply another word for heel-to-toe drop. When a brand lists a shoe as having an 8mm offset, it means the heel sits 8mm higher than the forefoot. The two terms, offset and drop, are used interchangeably across the industry.
Why it matters
Knowing that offset and drop are the same thing saves confusion when comparing shoes from different brands, since some quote one term and some the other. The number carries the same meaning: how much the heel is raised, and therefore how the shoe encourages your foot to land.
How it works
Like drop, offset is the heel stack minus the forefoot stack. It describes the geometry of the foam wedge under your foot, not the amount of cushioning. A low offset feels flatter underfoot; a high offset tips you slightly forward from the heel.
What to look for
When comparing shoes, treat offset and drop as the same figure. Keep it in a familiar range if your current shoes work well, and change it gradually if you want to move toward a flatter or more raised feel.
Common questions
Is offset the same as heel drop?
Yes, they are two names for the same heel-to-forefoot height difference.
Why do brands use different words?
It is just terminology. Some say offset, some say drop, but the measurement is identical.
What offset should I choose?
Whatever suits your stride. Stay near your current shoes' figure unless you are deliberately changing.
Does a low offset mean low cushioning?
No. Offset is only the heel-to-toe difference. Stack height describes the cushioning.
Is zero offset the same as barefoot?
A zero-offset shoe is flat heel to toe but can still be heavily cushioned, unlike a true barefoot shoe.
Key dimensions
Running Shoe Weight
What is running shoe weight?
Weight is how heavy a single shoe is, given in grams. Because weight scales with size, brands quote it for a standard sample size, often a men's UK 8 or 9, so always check the size a figure refers to when comparing two shoes.
Why it matters
You lift each shoe thousands of times in a run, so weight adds up. Lighter shoes reduce that effort and feel quicker underfoot, which is why racing shoes are stripped down. Heavier shoes usually trade some speed for extra cushioning, structure or hard-wearing materials.
How it works
Weight comes mainly from the midsole foam, outsole rubber and upper materials. A maximal cushioned trainer or a supportive stability shoe carries more of all three. Lightweight racers cut rubber coverage and use thinner uppers, which saves grams but can reduce durability.
What to look for
Decide what the shoe is for. For daily training, a little extra weight buys comfort and longevity. For racing and fast sessions, lighter is usually better. As a rough guide, under 230g is light, 230 to 300g is typical for a trainer, and above that is a cushioned or supportive build.
Common questions
What is a good running shoe weight?
Under 230g is light, 230 to 300g is a typical trainer, and heavier usually means more cushioning or support.
Do lighter shoes make you faster?
They reduce the effort of each stride and feel quicker, which can help, though fitness matters far more.
Why are some shoes so heavy?
Extra weight usually comes from more cushioning, stability features or durable rubber and upper materials.
What size is shoe weight quoted for?
Usually a men's UK 8 or 9. Always check, since a larger size weighs more.
Is a heavier shoe more durable?
Often, as it tends to carry more rubber and sturdier materials, though this is not a strict rule.
Lug Depth
What is lug depth?
Lug depth is how tall the individual grip studs stand on the bottom of a shoe, measured in millimetres. Road shoes have almost none; light trail shoes have 2 to 4mm; aggressive mud and fell shoes have 5mm or more.
Why it matters
On soft or loose ground, grip depends on studs sinking in and finding firm material below, so deeper lugs grip better off-road. But on hard-packed trails or tarmac, deep lugs reduce contact and feel awkward, and they wear down quickly. Depth has to match the surface.
How it works
Deeper lugs penetrate soft surfaces and, when widely spaced, shed mud as the foot lifts. Shallower lugs keep more rubber in contact with firm ground for a smoother, more stable ride. The spacing between lugs matters as much as their height.
What to look for
Pick lug depth for your usual terrain. Choose 5mm or more for soft mud and fells, 3 to 4mm for general trails, and 1 to 2mm or a road-style outsole for hard-packed paths and mixed road-to-trail running.
Common questions
What lug depth do I need?
5mm or more for mud and fells, 3 to 4mm for general trails, 1 to 2mm for hard-packed paths.
Are deeper lugs always better off-road?
Only on soft ground. On hard trails they cut contact, feel unstable and wear faster.
Do deep lugs work on roads?
Not well. They reduce contact, feel knobbly and wear down quickly on tarmac.
Does lug spacing matter too?
Yes. Wider spacing sheds mud better, while closer lugs give a smoother feel on firm ground.
How long do deep lugs last?
It depends on use. Running them on hard surfaces wears them faster than on the soft ground they are made for.
Toe Box Width
What is toe box width?
The toe box is the front section of the shoe around and ahead of your toes. Its width is how much side-to-side room there is for the toes to splay. Brands range from narrow, performance-fit toe boxes to deliberately wide, anatomical shapes.
Why it matters
Toes naturally spread as you land and push off, and a toe box that is too tight can cause rubbing, blisters, bruised nails and cramped comfort on long runs. Enough width lets the foot work naturally, while too much room can let the foot slide on fast or technical ground.
How it works
Toe box width is shaped by the last, the foot-shaped mould a shoe is built around. A wider last creates more splay room; a narrower last hugs the foot. Width usually pairs with volume, so a roomy toe box often has a little more height too.
What to look for
Feet swell on long runs, so allow room at the front, generally a thumb's width to the end. If you have wide feet or run long, favour a generous toe box. For short, fast or technical running, a snugger fit gives more control.
Common questions
How much toe room should a running shoe have?
About a thumb's width from your longest toe to the end, to allow for swelling and toe splay.
Are wide toe boxes better?
They suit wide feet and long runs, but a snugger fit can give more control for fast or technical running.
Can a toe box be too wide?
Yes. Too much room lets the foot slide, which can reduce control and cause rubbing.
What problems come from a tight toe box?
Blisters, bruised or black toenails, rubbing and cramped, uncomfortable toes, especially on long runs.
Does foot swelling affect toe box choice?
Yes. Feet swell during long runs, so leave extra room at the front rather than fitting tight.
Midsole Width
What is midsole width?
Midsole width is the side-to-side measurement of the foam platform your foot sits on, usually compared at the heel and forefoot. It is the footprint of the shoe, and it has grown wider on many cushioned models to keep tall stacks stable.
Why it matters
A wider platform spreads your weight over more area and resists tipping side to side, which adds stability, especially on a high stack. A narrower platform is lighter and feels quicker and more agile but gives less inherent support, asking more of your own balance.
How it works
Width works with stack height. As shoes get taller, a wider base stops them feeling tippy. Some shoes also flare the midsole outward at the heel or forefoot to add stability exactly where a runner needs it, without adding a traditional support post.
What to look for
If you want stability or run on a tall stack, a wider midsole helps you feel planted. If you prioritise agility and speed, a narrower platform feels sharper. Pair width with stack: tall and wide is stable, tall and narrow can feel unstable.
Common questions
Does a wider midsole mean more stability?
Yes. A broader base spreads weight and resists tipping, which is especially useful on tall, cushioned shoes.
Is a narrow midsole bad?
No, it is lighter and more agile. It just offers less built-in support and asks more of your balance.
Why are cushioned shoes getting wider?
To keep their tall foam stacks stable, since a high, narrow platform would feel tippy.
Does midsole width affect weight?
Somewhat. More foam across the platform adds a little weight compared with a narrower build.
Should I pick width based on stack height?
It helps. Tall and wide feels stable, while tall and narrow can feel unstable for many runners.
Heel Width
What is heel width?
Heel width is the side-to-side measurement of the platform beneath your heel. It is a specific part of the overall midsole footprint, focused on where most runners first contact the ground, and it strongly affects how a landing feels.
Why it matters
For heel strikers, the rearfoot takes the first impact, so a wider heel base spreads that load and steadies the landing, reducing the feeling of rolling inward or outward. A narrow heel feels lighter and quicker but gives the landing less margin for error.
How it works
A broad heel, sometimes flared outward, creates a larger, more stable contact area at touchdown. Some shoes use a crash pad or bevel at the heel to smooth the landing too. The heel base works with overall stack: a tall heel benefits from extra width.
What to look for
If you land heel-first or want stability on long runs, a wider, possibly flared heel feels more secure. If you run fast or land midfoot, a narrower heel saves weight and feels sharper without losing much, since you rely on the heel base less.
Common questions
Does a wider heel help heel strikers?
Yes. It spreads the first impact and steadies the landing for runners who contact heel-first.
Is a narrow heel unstable?
It can feel less planted at landing, but it is lighter and suits midfoot strikers who load the heel less.
What is a flared heel?
A heel that widens outward beyond the upper to create a broader, more stable landing base.
Does heel width matter for forefoot runners?
Less so, since they make little heel contact, so a narrower heel rarely troubles them.
How does heel width relate to stack?
A tall heel stack benefits from extra width to stay stable, while a low heel needs less.
Performance ratings
Flexibility Rating
What is a flexibility rating?
A flexibility rating is a guide to how much a shoe bends, most importantly at the forefoot where the foot flexes at toe-off. Ratings run from very flexible, where the shoe twists and folds easily, to very stiff, where it resists bending almost entirely.
Why it matters
Flexibility shapes how natural or how propulsive a shoe feels. A flexible forefoot lets your foot move and strengthen naturally and suits easy, slower running. A stiff forefoot, often from a carbon or nylon plate, stores and returns energy to roll you forward for faster running.
How it works
Flexibility comes from the midsole foam, any embedded plate, the outsole pattern and grooves cut into the sole. Flex grooves make a shoe bend more easily; a full-length plate or dense foam makes it stiffer. Stiffness can feel awkward slow but efficient at speed.
What to look for
Match flexibility to purpose. Choose a flexible shoe for easy runs, gym work or a natural feel. Choose a stiffer, plated shoe for racing and fast sessions where propulsion matters. Many runners keep both for different days.
Common questions
Is a flexible shoe better?
For easy, natural running, yes, but stiffer plated shoes are more efficient for racing and fast sessions.
Why are racing shoes stiff?
A stiff plate stores and returns energy and resists toe bend, helping roll you forward efficiently at speed.
Where does a shoe flex most?
Usually at the forefoot, where your foot bends to push off at toe-off.
What makes a shoe stiff?
A carbon or nylon plate, dense foam or a solid outsole with few flex grooves.
Should beginners avoid stiff shoes?
Many prefer a flexible, natural shoe for easy running and save stiff plated shoes for fast efforts.
Energy Return Rating
What is an energy return rating?
Energy return is how much of the force from each footstrike the midsole foam returns to you as it springs back to shape. A rating describes this on a scale from low, where the foam mostly absorbs and damps, to high, where it rebounds energetically.
Why it matters
A shoe that returns more energy reduces the effort of each stride and feels lively and fast, which is why modern racing foams chase high return. A lower-return shoe feels flatter and more controlled, soaking up impact for a calmer, more cushioned ride.
How it works
Modern foams compress under load and then rapidly rebound, pushing back as your foot leaves the ground. Newer materials store and return more of that energy than older ones. A plate can add to the sensation by stiffening the platform and snapping it back.
What to look for
For fast running and races, look for high energy return for a springy, efficient feel. For easy days and recovery, high return is less important, and a softer, more damped foam can feel more comfortable. Foam type is the biggest clue to expect.
Common questions
What does high energy return feel like?
Springy and lively, as if the shoe gives a little push back with each stride, reducing effort.
Does energy return make me faster?
It improves efficiency and feel, which can help, though fitness remains the main factor in speed.
Which foams have high energy return?
Modern lightweight performance foams, often paired with a plate, return more energy than older midsole materials.
Is high energy return good for easy runs?
It is less important. Many runners prefer a softer, more damped foam for easy and recovery miles.
Can a plate add energy return?
A plate stiffens the platform and can enhance the springy, propulsive feel, though the foam does most of the work.
Cushion Level
What is cushion level?
Cushion level is a guide to how much soft, protective foam a shoe puts between your foot and the ground, and how soft that foam feels. It is usually described from minimal, through balanced or moderate, to maximal, the plushest and most protective.
Why it matters
Cushioning absorbs impact, so more of it protects legs on long runs and recovery days and feels comfortable for many runners. Less cushioning gives ground feel, stability and a responsive ride that many prefer for fast, short efforts. The right level depends on the run and the runner.
How it works
Cushion level depends on both stack height and foam softness. A tall stack of soft foam feels maximal; a thin layer of firm foam feels minimal. Two shoes with the same stack can feel different if one foam is softer, so cushion is about feel as well as thickness.
What to look for
Choose more cushioning for long runs, recovery and high mileage, and less for speed, racing and ground feel. Very soft is not automatically better, as too much softness can feel unstable or vague. Match cushion to the job the shoe will do.
Common questions
Is more cushioning always better?
No. It protects long runs but can feel unstable or vague, while firmer shoes feel sharper for fast running.
What is a maximal shoe?
One with a very tall, plush stack of soft foam for maximum impact protection and comfort.
Does cushion level depend on stack height?
Partly. It depends on both how thick the foam is and how soft it feels underfoot.
Which cushion level suits long runs?
More cushioning generally suits long and recovery runs by absorbing repeated impact over distance.
Is minimal cushioning bad for beginners?
Many beginners prefer more cushioning at first, then explore firmer shoes as their running develops.
Stability Rating
What is a stability rating?
A stability rating tells you how much built-in support a shoe provides against the foot rolling inward too far as it lands. Ratings run from neutral, with no added correction, through stability, with moderate support, to motion control, the most structured.
Why it matters
Some runners roll inward more than is comfortable, which can feel unsteady or contribute to niggles. A stability rating helps you find a shoe that matches how your foot moves: neutral if you want the foam to stay out of the way, more support if you want guidance.
How it works
Stability is built with firmer foam on the inner edge, a wider base, midsole sidewalls that cradle the foot, or a guidance frame. Modern stability shoes tend to guide gently rather than force a correction, so they feel less intrusive than older designs.
What to look for
If your current neutral shoes feel comfortable and stable, you likely do not need added support. If you feel a strong inward roll or want a more planted feel, a stability shoe may suit. Choose based on comfort and feel rather than rules alone.
Common questions
What does a stability shoe do?
It gently resists the foot rolling inward too far, adding support and a more planted feel.
Do I need a stability shoe?
Only if you feel a strong inward roll or instability. Many runners are comfortable in neutral shoes.
What is motion control?
The most structured category, offering the firmest guidance for runners who need maximum support.
Is neutral the same as no cushioning?
No. Neutral refers to no added pronation support. Neutral shoes can be highly cushioned.
How do modern stability shoes feel?
They tend to guide gently with wider bases and sidewalls rather than forcing a firm correction.
Breathability Rating
What is a breathability rating?
Breathability is how freely air flows and sweat escapes through the upper of a shoe. A rating runs from highly breathable open meshes to sealed, water-resistant uppers that trade airflow for protection from cold and wet.
Why it matters
Feet sweat as you run, and trapped heat and moisture lead to discomfort and blisters. A breathable upper keeps feet cooler and drier in warm weather and dries quickly after rain or stream crossings. In winter, though, too much airflow lets in cold, so the ideal depends on the season.
How it works
Breathability comes from the upper material and weave: open engineered mesh lets air through freely, while tighter knits, overlays and waterproof membranes restrict it. Waterproof shoes seal out water but breathe less, so they run warmer and dry more slowly once wet inside.
What to look for
For summer and hard efforts, favour an open, breathable mesh to stay cool. For winter, wet trails or cold mornings, a more sheltered or water-resistant upper keeps feet warmer. Many runners pick breathable shoes for summer and a more sealed pair for winter.
Common questions
Why does breathability matter?
It keeps feet cool and dry, reducing heat, sweat build-up and the blisters that come with them.
Are breathable shoes good in winter?
Less so. They let in cold air, so a more sheltered or water-resistant upper suits cold, wet conditions.
Do waterproof shoes breathe well?
No. Sealing out water reduces airflow, so they run warmer and dry slowly once wet inside.
What makes an upper breathable?
An open, engineered mesh with few overlays lets air and moisture pass through freely.
Should I have different shoes for summer and winter?
Many runners do, choosing a breathable pair for summer heat and a sheltered pair for winter wet and cold.