Getting the fit right: length, width, heel and the evening rule

Stack, drop, plate, foam name, weight in grams: all of it is downstream of whether the shoe fits. A 210 g carbon racer that pinches at the fifth toe is slower over a marathon than a 280 g trainer that does not, because you will change how you run to protect the sore spot. That is not a figure of speech. It is the ordinary reason people finish a race limping in the fastest shoe they own.

Fit is also the only part of this decision that cannot be delegated. A catalogue can tell you that a shoe has a 37 mm heel stack, an 8 mm drop and a wide last. It cannot tell you where your longest toe ends or how much volume sits over your instep. So do the fit yourself first, then let the specs break the tie — that is the order the pillar guide works in, and the order the finder asks its questions in.

Three measurements do almost all the work: length, measured to the longest toe rather than the big one; width, measured at the ball of the foot and checked against where the shoe bends; and heel hold, which is a yes or a no. Everything else — arch shape, instep volume, toebox height — is a refinement on top of those three.

Stand up in the shoe, weight on both feet, and press down in front of the longest toe. You want roughly a thumb’s width of empty space — about a centimetre — between the end of that toe and the end of the shoe. Sitting down does not count: the foot lengthens under load, and you will be running on it, not sitting on it.

The phrase that matters there is longest toe, not big toe. A large minority of people have a second toe longer than the first, and it is a normal foot shape rather than a problem to be corrected. If you size to the big toe out of habit, that second toe spends every downhill kilometre pressed into the front of the shoe. Black toenails are almost always this, and almost never bad luck.

Too long is a real failure too, though it is rarer and more forgiving. A shoe with two centimetres of dead space in front lets the foot slide on landing, moves the flex point forward of your toe joints, and blisters the ball rather than the toes. The symptom is different from a shoe that is too short, so you can tell them apart from the damage.

Width is not one measurement, it is an alignment. The widest part of your foot — the ball, across the heads of the metatarsals — has to land on the widest part of the shoe. If your foot is wider further back or further forward than the shoe expects, the shoe will feel tight even when the number on the box says it is your size.

The second half of the check is the flex point. Hold the shoe by the heel and the toe and bend it. It will crease in one place. That crease has to sit under the joints where your own foot bends, which is the same line across the ball. A shoe that flexes behind your toe joints fights every push-off; one that flexes ahead of them gives you no leverage at all and rubs where the upper folds in the wrong place.

Toes should be able to splay sideways when you land. Press across the widest point with a thumb and forefinger: you want the upper to move, not to be stretched drum-tight over the little toe. Mesh gives a little over the first hundred kilometres, but the last underneath it does not — a shoe that is narrow at the sole will still be narrow in a month.

Length and width have tolerances. The heel does not. Lace the shoe normally, then walk and rise onto your toes. If the heel lifts off the footbed, the shoe is wrong — or the lacing is. Nothing else in fit is as binary, because a heel that moves is a blister with a delivery date.

Before you reject the shoe, try the lacing. The extra eyelet at the top of almost every running shoe exists for this: thread the lace back through it on the same side to make a loop, pass the other lace through that loop, and pull down and back rather than up. It pulls the collar into the hollow above your heel bone without tightening the rest of the shoe. It fixes a surprising number of heels that felt hopeless out of the box.

1. 1

   Loosen everything first

   Open the laces fully and put the foot in without forcing it. Half of all heel slip is a foot that never got back into the heel cup, and you cannot judge the shoe until it has.

2. 2

   Tap the heel down

   Stand, knock the heel back against the floor, and let the foot settle into the counter before you tighten anything. Lacing a foot that is sitting forward locks it in the wrong place.

3. 3

   Lace from the toe up

   Snug each pair of eyelets in turn rather than pulling the whole lace tight from the top. Pressure over the instep should be even, not concentrated in one band.

4. 4

   Add the runner’s loop if it slips

   Use the top eyelet to make a loop on each side, cross the laces through, and pull down and back. Tie off with the ankle bent, not pointed.

5. 5

   Walk, then rise onto your toes

   Twenty steps and three calf raises tell you more than ten minutes of standing. If the heel still lifts, it is the shoe. Put it back.

Your feet are bigger in the evening than in the morning, and bigger at the end of a run than at the start. Standing and walking pushes fluid down into the tissues of the foot; running does that and sends far more blood to the working muscles of the lower leg and foot besides. The arch also flattens slightly under repeated load, which lengthens the foot as well as widening it. None of that is a defect. It is what a foot does when you use it.

The practical consequence is that a shoe fitted first thing on a Saturday morning can be a size too small at kilometre 25 of a Sunday long run. So try shoes late in the day, or immediately after a run if you can manage it, and always in the socks you actually run in. Sock thickness is worth a meaningful fraction of a half size, and a fit judged in thin cotton socks will not survive winter.

If you use an insole, an orthotic or a thicker aftermarket footbed, bring it and fit the shoe with it in place, having taken the stock one out. An insole occupies volume. Fitting the shoe without it and adding it later changes the fit in every direction at once.

A shoe size does not describe your foot. It describes the last — the foot-shaped form the shoe was built around — and every brand has its own lasts, developed on its own reference feet and carried forward through decades of models for the sake of consistency with itself rather than with anyone else.

The conversion tables make it worse. EU, UK and US sizing are three different scales with different starting points and different step sizes, and the mapping between them is a convention rather than a rule. The one system that states a foot length honestly is Mondopoint, standardised as ISO 9407, which gives the length of the foot in millimetres — and outside Japan it is the system almost no running shoe prints on its box. Ski boots use it everywhere; Japanese running shoes are sold in centimetres of foot length under JIS S 5037; most of the rest of the world still sells you a number that means nothing on its own.

So treat your size as a starting guess and the shoe in front of you as the evidence. Being a 43 in one brand and a 43.5 in another is not an inconsistency to be resolved; it is two lasts of different lengths wearing the same label. If you buy online, buy from somewhere that takes returns on a shoe worn indoors, and do the thumb check on the carpet before the shoe ever sees tarmac.

• Race shoes generally run snugger than daily trainers from the same brand — the fit is deliberate, and it is part of why they feel fast. See carbon plates and super shoes for what else comes with that.
• Trail shoes are often built tighter through the midfoot to stop the foot sliding on off-camber ground. That is a feature on a mountain and an annoyance on a canal path — road versus trail covers where each belongs.
• A model number change is a new last more often than the marketing admits. Loving the v12 is weak evidence about the v13, so re-check the fit rather than re-ordering blind.
• Left and right feet differ, sometimes by half a size. Fit the larger one and adjust the other with lacing.

Of the 78 shoes in this catalogue, 57 are built on a standard medium last, 11 on a wide or genuinely foot-shaped one, and 10 on a narrow one. That distribution is the single most useful thing to know before you start shopping, because it tells you how much of the market is actually open to you.

If you fit a medium last, almost everything here is available and fit will rarely be the constraint. If you need width, the pool is 11 shoes — and they are concentrated in four brands out of fifteen: New Balance builds six of them, Altra three, with one each from Topo Athletic and Hoka. Knowing that saves you the discovery process. They run from €140 to €180, so width is not a premium you pay for; it is a shape you have to go looking for.

The narrow ten are a different story, because narrowness there is mostly a by-product of purpose rather than a fit option. Six of the ten carry a carbon plate, which is 6 of the 14 carbon shoes in the catalogue; three of the remaining four are trail shoes built to hold the foot still on rough ground. Race lasts are narrow because a foot that cannot move inside the shoe transmits force better, not because narrow feet are the target market.

The uncomfortable corollary: if you have wide feet and you want a carbon race shoe, that is a genuine conflict rather than a search problem, and fit should win. A plate you cannot tolerate for two hours buys you nothing.

Once the shape is right, the numbers are worth reading — and stack height and drop explained is the place to start, because those two are the specs most often confused with each other. If something hurts rather than merely rubs, shoes and running injuries is honest about what a shoe can and cannot do about it.