Why running shoes should be bigger than everyday shoes
When running, the foot swells, through heat, load and the pumping motion of every step. On long runs it can become noticeably larger. In addition, the foot slides forward downhill and when braking. If there is no room at the front, the toes repeatedly hit the tip of the shoe, the classic cause of pressure points and the dreaded "runner's toe" (black toenail). That is why running shoes are deliberately chosen with a little more room than a street shoe or sneaker that you only wear for walking.
The thumb's width rule
The simplest rule of thumb: there should be about a thumb's width of room between your longest toe and the end of the shoe, roughly one centimetre. The longest toe is not the big toe for everyone; for many people the second toe is longer. This is how you check:
- Test standing, not sitting: Stand upright so that the foot expands fully under load.
- Thumb across in front of the toe: About a thumb's width should be free at the front. If it is much less, the shoe is too short.
- Secure the heel: At the same time the heel must sit firmly and not slip out when rolling through the stride. Too much room is just as bad as too little.
Well-cushioned long-run shoes such as the ASICS Gel-Nimbus 26, the Saucony Triumph 22 or the New Balance Fresh Foam X More v5 are often used for long distances, where the foot swells the most. The thumb's width check is especially worthwhile here.
Measure in the evening, and both feet
Feet are not the same size all day. Fluid accumulates over the day, and in the evening they are at their largest, similar to after a long run. If you try shoes on in the afternoon or evening, you get a more realistic size. Three points help:
- Measure both feet: Almost everyone has one slightly larger foot. Always go by the larger one.
- Try on with running socks: Thin everyday socks distort the fit. Use the socks you actually run in.
- Know your foot length: Measure the length from the heel to the longest toe in the evening, standing, on a sheet of paper. This number in centimetres helps more with online shopping than any standard size number.
Half a size up? Usually yes
Many runners choose their running shoe half to a full size bigger than their everyday shoe, precisely to leave a thumb's width at the front. It is not a rigid rule: some models run long from the start, others short. Still, half a size up is a good starting point for trying on. Popular everyday trainers that are good for experimenting with this are the Nike Pegasus 41, the Brooks Ghost 16, the Hoka Clifton 9, the ASICS Gel-Cumulus 26 and the Saucony Ride 17.
Length isn't everything: width matters too
A shoe can be the right length and still pinch if it is too narrow in the forefoot. Length and width are two separate measurements. If a shoe feels tight at the sides, going up a size usually doesn't help, because then it becomes too long at the front. A wider fit or a different model does. Some manufacturers offer the same models in several widths; others build with a wider toe box from the ground up. Altra, for example, deliberately relies on plenty of room in the forefoot with its "FootShape" design, as in the Altra Torin 8 or the lighter Altra Escalante 4. Which models run wider and where widths are available is covered in the guide Running shoes for wide feet.
Do brands fit differently?
Tendentially yes, but less dramatically than is often claimed. Two things cause confusion:
- Different sizing systems: EU, UK and US count differently. The same EU "42" does not correspond to the same US number. When buying online, go by the manufacturer's centimetre measurement, not just the standard size.
- Different lasts: Each brand builds its shoe around its own foot shape (the last). One is slimmer, another cut rounder. That is why your usual size can feel different from brand to brand.
Only trying on settles this reliably. If you're torn between two models, put them side by side in the comparison; the full selection with filters for cushioning and use is shown in the running shoe overview.
How to check the fit in the shop
- Walk or run a few steps: Don't just stand, move around. Many specialist shops have a treadmill.
- Check the heel fit: The heel must not slip up as you roll through the step. Targeted lacing (a heel lock through the top eyelets) can help.
- Watch for pressure points: Nothing should pinch or rub. A running shoe must fit from the first step, and "breaking in" is a myth with shoes that are too tight.
- Consider neutral or support: Whether you need a neutral or a support shoe is independent of size. The guide Neutral or support shoe? covers that.
Soft max-cushioned shoes such as the Hoka Bondi 8, the Nike Invincible 3 or the adidas Ultraboost 5 feel different at first from flat, responsive shoes like the New Balance FuelCell Rebel v4 or the Hoka Mach 6. That also affects which size feels "right".
Putting it honestly
There is no formula that tells you the perfect size without trying on, as feet and lasts are too different. The thumb's-width rule, measuring in the evening and half a size up are proven starting points, not dogma. If in doubt, buy where you can exchange easily, and go by how it feels when you run rather than the number in the shoe. To narrow down suitable models, the shoe finder, the running shoe overview and further guides such as Heel drop explained simply can help.
Frequently asked questions
Should you buy running shoes a size bigger?
As a starting point, yes: many runners choose their running shoe half to a full size bigger than their everyday shoe so that about a thumb's width (around 1 cm) of room remains at the front. It is not a fixed rule, though: some models run longer, others shorter. What matters is not the number but that a thumb's width is free at the front and the heel sits firmly. If in doubt, try on two sizes.
How much room should there be in front of the toes?
About a thumb's width, so around one centimetre between the longest toe and the end of the shoe. Check this standing, not sitting, because the foot expands under load. Note: the longest toe is not the big toe for everyone, and for many people the second toe is longer.
Why should you try on running shoes in the evening?
Because feet swell over the course of the day and are largest in the evening, similar to after a long run. If you try on in the morning, you easily choose a shoe that is slightly too tight. So measure and try on in the afternoon or evening, with your actual running socks, and go by the larger of your two feet.
Do all brands fit the same?
No. Each brand builds its shoe around its own last (foot shape), and EU, UK and US sizes count differently. That is why your usual number can feel different from model to model. When buying online, the manufacturer's centimetre measurement helps more than the standard size alone. In the end, only trying on is certain.
How can I tell that the running shoe is too small?
Typical signs: your toes hit the front on downhills, your toe tips hurt after longer runs or a toenail turns dark (the black "runner's toe"). Pressure at the sides of the forefoot also suggests too little room, but then the width is often the problem, not the length. A running shoe must fit from the first step; "breaking in" does not fix shoes that are too tight.
Length or width: which matters more?
Both matter, and they are independent of each other. A shoe can be the right length and still pinch at the sides. If it pinches across the front, going up a size usually doesn't help, because then the shoe becomes too long. A wider fit or a model with more room in the forefoot does. Which models run wider is covered in the guide Running shoes for wide feet.