Measure Your Shoe Size in Millimetres, Allow 5–12mm for Toe Room

by YDA UK

Measure your larger foot heel to longest toe in millimetres. That single number, checked against a brand’s own size chart, is what you use to pick a size. Take the measurement standing, in the socks you plan to wear, and check the width column too if the chart has one, since length alone misses a fair share of poor fits.

TL;DR:

  • Measure your foot heel to longest toe while standing in socks to account for swelling and load, and record the larger foot’s length.
  • Use a firm, flat floor and a wall, marking the tip of the longest toe and the widest part of the foot to ensure accurate measurements in millimetres.
  • Always compare your measurements with the specific brand’s size chart, not generic conversions, and prefer sizing up when between two sizes.
  • Check the internal shoe length, which is typically 5 to 12 millimetres longer than your foot, for better fit in your chosen shoe style.
  • Verify the fit after purchase by confirming heel lock, heel slippage, toe space, and overall comfort, avoiding assumptions that shoes will stretch over time.
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Table of Contents

What you need before you start measuring

You do not need special kit for a reliable home measurement, just a few household items and the right conditions. Gather these before you begin:

  • A firm floor (not carpet), a sheet of paper, a pen, and a ruler or tape measure.
  • A wall or straight edge to line the paper against.
  • Socks, if you plan to wear them with the shoes you are buying.

Timing matters as much as tools. Feet swell slightly through the day, so measure in the evening when they are at their fullest rather than first thing in the morning. Stand rather than sit, with your weight distributed evenly across both feet, since sitting lets the foot flatten and lengthen less than it would under load.

Measure both feet separately. Most people have one foot slightly longer than the other, and the size you buy should match the larger one. Run through this quick checklist before you pick up the pen: firm floor ready, paper flat against the wall, correct socks on, weight evenly placed, both feet ready to measure. Once those are in place, the actual measurement takes only a minute or two.

Step-by-step home measurement method you can trust

This method mirrors the logic behind the Brannock device, the metal foot gauge used in shoe shops for decades, adapted for a kitchen floor and a sheet of paper.

  1. Place a sheet of paper flat against a wall on a hard floor.
  2. Stand on the paper with your heel touching the wall and your weight evenly spread.
  3. Ask someone to mark the tip of your longest toe on the paper. This is not always the big toe: for some people the second toe extends furthest.
  4. Step off and measure the straight-line distance from the wall edge to the mark in millimetres or centimetres.
  5. Repeat for the other foot and record both numbers.
  6. Take the larger of the two measurements. That is the value you use for sizing.
  7. While still standing on the paper, mark the widest points of your foot on each side (usually across the ball of the foot) and measure the distance between them for your width.
  8. Note your toe shape (square, tapered, or one toe longer than the rest) since it affects how much room you need at the front of the shoe.

Measure each foot twice. If the two readings differ by more than a couple of millimetres, average them rather than guessing which was correct. Doing this alone is fiddly since you are trying to mark your own foot while balancing on it, so it helps to have someone else hold the pen while you stand still.

The Brannock device instructions also stress comparing heel-to-toe length against arch length, the distance from your heel to the ball of your foot. A mismatch between the two, common in people with unusually long toes or a short arch, is a sign that standard sizing may not fit well regardless of overall length, and that trying a half size up or down is worth doing at the fitting stage.

Pro Tip: Measure in the actual socks you will wear with the finished shoes, whether that is thin dress socks or thick hiking socks, since sock thickness can shift the fit by half a size. Keep a written record of both foot lengths and widths so you never have to remeasure for future purchases.

Once you have your numbers, end-to-end guides on measuring at home can help you cross-check your method before you move on to reading a size chart.

Converting your measurement into UK, EU or US sizes

A foot length in millimetres only becomes useful once you map it to a size chart, and this is where most confusion starts. Size charts convert a length measurement into a shoe size using a scale that differs slightly between the UK, US and EU systems, and between men’s, women’s and children’s ranges within each. The EU system, sometimes called mondopoint-adjacent, is based roughly on the length of the shoe’s last in centimetres rather than the bare foot, which is one reason a EU size does not translate to a single fixed millimetre figure across every brand.

Converting your measurement into UK, EU or US sizes — overview diagram

This distinction between foot length and shoe internal length matters more than most buyers realise. The inside of a shoe (its insole or mondopoint length) is built slightly longer than the foot it is meant to hold, to leave room at the toe for natural movement and swelling. Lab measurements suggest that internal shoe length typically runs 5 to 12 millimetres longer than foot length, with athletic shoes generally needing a toe allowance nearer the higher end of that range because of the extra motion involved in running or training. There is no single number that applies to every shoe, so treat this as a starting range rather than a fixed rule.

When you have your measurement, work through it like this:

  • Find the brand or retailer’s own size chart rather than relying on a generic conversion table, since the same foot length can land on different sizes at different brands.
  • If the chart lists an insole or internal length, compare it directly to your foot length plus a small allowance rather than to your foot length alone.
  • When your measurement falls between two sizes, size up rather than down for most everyday and athletic shoes, since a shoe that is slightly too big is easier to live with than one that is slightly too small.
  • Check the brand’s returns policy before you order if you are unsure, so a wrong guess costs you nothing but time.

Rounding matters too. Round to the nearest listed size when your measurement sits close to the midpoint, round up when the shoe type needs extra room (running shoes, boots, safety footwear), and round down only when the brand explicitly recommends a snug fit, such as some cycling shoes or dress shoes designed to mould to the foot. YDA’s own conversion guide sets out this kind of brand-specific mapping for readers converting a raw measurement into a size they can actually order. If you are converting specifically towards US listings, a dedicated US size chart will save you from guessing at the offset.

Width, instep and other fit factors you must check

Length gets most of the attention, but it is only half the fit equation. A shoe that matches your foot length perfectly can still pinch, slip, or press down on the top of your foot if the width and instep do not match as well.

To measure width, stand on your traced outline again and mark the widest points across the ball of your foot, the spot just behind your toes where the foot is broadest. Measure the straight-line distance between those marks in millimetres. Some retailers also ask for girth, the measurement right around that widest part of the foot, which captures how much the foot bulges rather than just how far it spreads.

Width is usually shown with a letter code such as B, D, E or 2E, running from narrow to wide, though the exact millimetre range behind each letter is not standard across brands. A “D” width from one manufacturer is not guaranteed to match a “D” from another, which is why checking the brand’s own width notes matters more than memorising the letters themselves.

Instep height, the vertical distance from the top of your foot to the floor at its highest point, is a separate factor again. A high instep needs more room in the vamp (the upper part of the shoe covering the top of the foot), while a low instep can leave extra material that causes slipping.

Foot shape varies more than most buyers expect. Research into foot width and instep height has found wide dispersion across both measurements in the population, which is one reason a single width option per length rarely satisfies everyone, and why brands offering multiple width fittings tend to serve a broader range of feet well.

Practical steps that follow from this:

  • Check whether the brand offers multiple width fittings, and choose accordingly rather than defaulting to standard.
  • If your instep is unusually high, look for lace-up styles with more adjustment room rather than slip-on designs.
  • Use a thin, supportive insole if a shoe fits in length but feels tight across the top of the foot.

Common mistakes and a quick check when your shoes arrive

Most sizing complaints trace back to a handful of avoidable errors made during measurement, not to the shoes themselves.

  1. Measuring while seated, which lets the foot sit shorter than it does under weight.
  2. Measuring on carpet or another soft surface, which distorts the paper and blurs the toe mark.
  3. Using the smaller foot’s measurement instead of the larger one.
  4. Forgetting to allow for toe room, and picking a size that matches foot length exactly with no allowance at all.
  5. Skipping the width check entirely and assuming a standard fitting will work.

Once your shoes arrive, run through a short check before deciding whether to keep them. Confirm the heel sits locked in place with no lifting when you walk. Check the midfoot feels snug without pinching across the widest part of the foot. Press down and confirm roughly a thumb’s width of space between your longest toe and the front of the shoe. Walk around the room, wriggle your toes, and check nothing slips at the heel or presses at the sides.

If any of these checks fail, exchange for a different size or width rather than assuming the shoe will “break in” to fit, since a shoe that is genuinely the wrong size rarely improves with wear. Most retailers, including specialist footwear retail categories, set out clear return windows for exactly this reason, so use them rather than persevering with a poor fit.

Why accurate measurement matters, and where to find YDA’s sizing resources

Getting this right at home saves a return, a delay, and the disappointment of a shoe that never quite feels comfortable. This guide draws on established fitting principles, from Brannock-style heel-to-toe measurement through to the toe allowance and width guidance used across the footwear industry, to give you a method you can trust without needing a shop visit.

YDA’s own sizing resources build on the same principles. The Technology of YDA Shoes pages explain the foot-health thinking behind the brand’s fit, and the 2026 conversion guide applies the measurement method in this article directly to reading a size chart. If you want a narrower conversion, such as translating a specific centimetre figure straight into a UK size, the centimetre-to-UK conversion guide covers that step in detail.

Accounting for foot swelling during exercise or long wear

Feet do not stay the same size all day. They tend to swell with heat, activity, and time spent standing or walking, which is part of why measuring in the evening rather than the morning gives a more useful number for everyday shoes.

If you are buying shoes specifically for running, hiking, or long shifts on your feet, measure after a walk or a light workout rather than at rest, so the measurement reflects the size your foot reaches under the conditions the shoe will actually see. Long flights, hot weather, and standing for extended periods all cause similar swelling, and shoes bought to fit a foot at its smallest tend to feel tight by the afternoon.

This is also where a slightly larger toe allowance earns its place. A shoe with a little extra room at the front absorbs the natural lengthening that comes with swelling, whereas a shoe sized to the exact morning measurement can start pressing on the toes within an hour of activity. For anyone managing a foot condition where swelling is more pronounced, such as diabetes-related foot changes, checking fit later in the day and allowing a touch more room throughout the shoe, not just at the toe, is worth doing before committing to a size.

Tips for measuring children’s feet accurately

Children’s feet grow quickly and change shape between measurements, so the same heel-to-toe method applies but needs a bit more patience and more frequent repeating.

Measure a child’s foot standing, not sitting, since children shift their weight unevenly when seated and the reading can come out shorter than the real size. Do it towards the end of the day if possible, though with younger children this is not always practical, so measuring after they have been up and moving for a while is a reasonable substitute.

Leave a little more growing room than you would for an adult shoe, since children’s feet can grow noticeably within a few months, but avoid sizing so far up that the shoe affects how they walk. A shoe that is too loose can cause tripping or an unnatural gait just as easily as one that is too tight. Check both length and width, since children’s feet are often proportionally wider than adult feet, and recheck the measurement every few months rather than assuming last season’s size still fits.

What actually matters when you are sizing yourself

Most sizing advice fixates on finding the “correct” size as though it were a single fixed number, when in reality a size is a rough estimate that still needs verifying on your actual foot. The measurement step matters, but it is the floor of good fit, not the ceiling. Skipping the width check is the most common failure I see in sizing advice generally: people obsess over getting length to the millimetre and then buy a standard width without ever checking whether their foot is unusually broad or high at the instep.

The conventional advice to “measure your foot and buy that size” undersells how much brand variation there is in shoe internal length. Two shoes with identical listed sizes can differ by a centimetre inside, which is why a brand’s own chart, not a universal converter, should always have the final word.

If you take one thing from this, prioritise the try-on checklist over the tape measure. A measurement gets you close. Walking, wriggling, and checking for slip is what confirms you actually got there.

— Panagiotis

Ready to put your measurement to use

Once you have your foot length, width and a size in hand, choosing a shoe becomes a much shorter job. Ydauk’s high performance footwear range is built around foot health and energy efficiency, with the fit thinking behind it explained on the Technology of YDA Shoes pages, so the size you have just measured maps straight onto a shoe designed to support that shape through every step. Rather than guessing between generic listings, take your recorded length and width and check them against the brand’s specific sizing notes before you order.

Browse the current high performance footwear range and use the measurement you have just taken to pick your size with confidence.

Sources

FAQ

What foot size is size 7?

There is no single millimetre figure that applies everywhere, since the exact length behind a size 7 varies slightly between brands and between UK, US and EU systems. The safest approach is to measure your foot length in millimetres and check it against the specific brand’s own size chart rather than assuming a fixed conversion.

What is 42 in shoe size?

EU sizes sit broadly in the adult men’s mid-range in most European charts, but the exact foot length they represent differs slightly by brand and shoe type. Measure your own foot length and compare it to the retailer’s chart rather than relying on a generic EU-to-foot-length table.

How do I check my UK foot size?

Measure your larger foot heel to longest toe while standing, in the socks you plan to wear, then compare that measurement in centimetres or millimetres against a UK size chart from the specific brand you are buying. Always check width alongside length, since UK sizing alone does not capture fit across the ball of the foot.

Can I measure my shoe size with my phone?

Some phone-based methods use a reference object, such as an A4 sheet, alongside the camera to estimate foot length and width, and calibrated image-based systems have reported mean errors under 3 millimetres for length and width when set up correctly. A simple paper-and-ruler measurement at home remains just as reliable for most everyday shoe purchases.

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