Shoe Size Converter

What Is Shoe Size?

Nothing in a US 10, a UK 9.5 or an EU 43 measures a foot. Each is a mark on a shoe, and the scales disagree because three shoemaking trades started counting from three different places with two different rulers.

What the Number Actually Measures

ISO 9407:2019 defines a shoe size as the designated size marking of a shoe or last made for a given foot length. The size is therefore a property of the shoe; foot length is the input that chooses it. The same standard fixes how that input is taken: the longest horizontal distance from the back of the heel to the end of the most prominent toe, measured along the inside tangent, standing, barefoot or in thin hose, with body weight equally distributed on both feet.

The gap between the two is where sizing gets its slack. A shoe has to be longer inside than the foot it holds, and ISO/TS 19407 sets that toe allowance at two size grades — 13.34 mm on the European scale, 16.94 mm on the UK scale. This calculator uses a flat 1.5 cm when it builds the EU column, which is close to the European figure and part of why the two disagree slightly.

The Four Scales, and the One They Leave Out

Enter a US men's 10 and the panel prints four numbers plus a length. Each column below counts something different, and only the last two count anything you can put a ruler on.

Mondopoint is the one system that refuses to abstract. ISO 9407 requires the foot length in millimeters as an integer, marked on the shoe as MP271 or Mondo 271, with the linear width of the foot allowed after a slash. Chinese and Japanese sizing already works this way, which is why a Japanese box says 27 or 271 rather than 43. This tool prints the centimeter figure, not an MP label — but 27.1 cm and MP271 are the same statement.

Fingers run into the same problem, with a US number, a UK letter and a European millimeter figure all naming one band, untangled in the Ring Size Calculator.

Why One Foot Has Four Different Numbers

The English-speaking scales were built out of the barleycorn, a third of an inch, and ISO/TS 19407 records both the UK and US systems as an 8.47 mm grading interval. Because an inch is exactly 25.4 mm, that third is 8.4667 mm and three whole sizes fill an inch of foot. Both scales also run out and restart: their first 13 sizes are children's sizes, after which the numbering begins again at 1 for adults, which is why a child's 13 and an adult 1 are neighbors rather than twelve sizes apart.

The European scale counts Paris points of ⅔ cm — 6.67 mm in the standard — from zero, and a smaller step means the numbers climb faster. Between a 22 cm foot and a 30 cm foot the US men's scale moves 9.4 sizes while the European scale moves 12 points. That mismatch is structural, and no conversion table can make two ladders with different rungs line up at every step.

How Do You Calculate Shoe Size?

Every column the panel prints descends from one quantity, and the conversions are four straight lines drawn through it.

The Shoe Size Formula

US Men   = 3 × foot length in inches − 22
UK       = US Men − 0.5
US Women = US Men + 1.5
EU       = (foot length in cm + 1.5) × 1.5

Foot length in cm     = (US Men + 22) ÷ 3 × 2.54
Foot length in inches = foot length in cm ÷ 2.54

Three of the constants are conversions rather than opinions. The 3 is three barleycorns to the inch. The 2.54 is exact: NIST records the inch as exactly equivalent to 25.4 mm since the 1959 international yard agreement. The 1.5 multiplying the EU line is Paris points per centimeter, since one point is ⅔ cm. The conventions are the rest: the 22 that sets where the US men's scale starts, the 0.5 and 1.5 that place the UK and women's scales against it, and the 1.5 cm of toe allowance added before a foot length becomes a European size.

The 22 is easier to read backward. Put a US men's 1 into the first line and the foot length that satisfies it is 7⅔ inches; a US men's 8 is exactly 10 inches, and a US men's 20 is exactly 14. Half a size is a sixth of an inch, 4.23 mm of foot, which is the resolution the whole system works at.

Whatever you type, the calculator converts it to the US men's scale first, works the foot length out from there, and derives the other three columns from that length. That single order of operations is why the four columns can never contradict one another, and why a European half size comes back out as itself — the EU column is that same foot length re-expressed and rounded to the nearest half point, so EU 42 in returns EU 42 out. What does shift is a two-step trip made by hand: enter EU 42, then re-type the US Men 9.5 it printed as a fresh entry, and the European column reads 42.5. The limits section takes that apart.

Step by Step

• Decide which number you actually have: a US men's size, a US women's size, a UK size, a European size, or a foot length in centimeters. The centimeters are the only one of the five that is a measurement.
• Convert to the US men's scale. From US women's, subtract 1.5. From UK, add 0.5. From centimeters, divide by 2.54, multiply by 3 and subtract 22. From a European size, divide by 1.5 and subtract 1.5 cm of toe allowance to get the foot length first, then apply the centimeter step.
• Get the foot length: add 22, divide by 3, multiply by 2.54. That is the length in centimeters; divide by 2.54 again for inches.
• Read the other scales off the men's figure: subtract 0.5 for UK, add 1.5 for US women's.
• Build the European size from the length, not from the men's size: add 1.5 cm, multiply by 1.5.
• Round each column to the nearest half. The rounding happens once, at the end, on each column independently — which is why the printed columns still sit exactly 0.5 and 1.5 apart.

Worked Example: a 27.1 cm Foot

Choose Foot length (cm) and enter 27.1. Dividing by 2.54 gives 10.6693 inches; times 3 is 32.0079; minus 22 is 10.0079, which rounds to US Men 10. UK comes off that raw figure at 9.5079 and US Women at 11.5079, printing 9.5 and 11.5. The European column starts again from the length: 27.1 plus 1.5 cm of allowance is 28.6 cm, times 1.5 is 42.9 Paris points, which rounds to EU 43.

Calculator output — Your Size System: Foot length (cm), Your Size: 27.1

US M 10 · US W 11.5 · UK 9.5 · EU 43

Below the headline the panel adds the line "Foot length ≈ 27.1 cm (10.7″) on the Brannock scale". The inch figure is the centimeter figure converted, and it is worth knowing it converts the rounded one: 27.1 ÷ 2.54 = 10.67, which prints as 10.7.

That last phrase names the measuring device found in American shoe stores rather than a published equation — the device reads a size straight off the foot. What the calculator runs is the US men's barleycorn scale, three sizes to the inch, and ISO/TS 19407 derives the same line from foot length by a completely different route. The limits section shows how closely the two land.

Working Backward From a Size You Already Know

Most people arrive with a size rather than a measurement, so all five modes run the same machinery in reverse. Three real conversions, each taken from the calculator:

Only the European entry takes an extra step. A EU 42 is divided by 1.5 to get 28 cm of shoe, then the 1.5 cm allowance comes back off to leave a 26.5 cm foot, and that length drives everything else. The other three modes are pure addition and subtraction on the men's scale before the length is ever computed.

Entering 26.5 in Foot length (cm) mode returns the identical line, which is the useful check: if a size and a measurement disagree in this tool, the measurement is the one that came from your foot.

Shoe Size Chart: US, UK, EU and Centimeters

Every row in this section is the calculator's own output, generated by entering the value in the first column. Nothing here is copied from a brand chart.

Men's Shoe Size Chart: US 6 to US 14

Enter the US Men figure and the rest of the row is what comes back. The foot length column is printed exactly as the panel prints it, which is why 7.5 shows as 25 cm rather than 25.0.

The men's column above ends at 14 for room, not because the tool does: it accepts US Men from 1 up to 20, and a 20 is a 35.6 cm foot.

Women's Shoe Size Chart: US 5 to US 13

The same rows entered in US Women mode. Because the women's scale is the men's scale plus 1.5 here, this table is the one above shifted, not a separate calculation.

One row is worth memorizing if you shop across both departments: a 25.4 cm foot is a US Men 8 and a US Women 9.5, and that 1.5-size step is the American retail convention rather than an international one. ISO/TS 19407 records a one-size difference between the two, a disagreement priced out further down.

Foot Length Chart: Centimeters to Every Size

This is the table to use if you have measured. Enter the length in Foot length (cm) mode and the whole row comes back.

Read the US Men column downward and you will see it skip: 23.0 cm gives a 5, 23.5 cm gives a 6, and the 5.5 in between never appears. Nothing is broken. Half a centimeter is 0.59 of a US size, so roughly one step in five jumps a US half size instead of landing on the next one. US Men 5.5 belongs to a 23.3 cm foot, which the ladder steps straight over, and the same thing happens twice more in this table — between 26.0 cm and 26.5 cm, and between 28.5 cm and 29.0 cm.

The lesson for buying is that centimeters resolve finer than sizes do, not coarser. If two rows both look plausible for your foot, the one nearer your measured length wins.

EU Sizes the Men's Ladder Never Prints

Walk the men's chart from US 4 to US 16 in half sizes and the EU column reads 35.5, 36, 36.5, 37, 38, 38.5, 39, 39.5, 40.5, 41, 41.5, 42.5, 43, 43.5, 44, 45, 45.5, 46, 46.5, 47.5, 48, 48.5, 49, 50, 50.5. Six European half steps inside that span are missing: 37.5, 40, 42, 44.5, 47 and 49.5.

The arithmetic behind the gap is simple. One US size is 0.847 cm of foot, which is 1.27 Paris points; a US half size is 0.635 of a point. Rounded to the nearest half point that alternates between a 0.5 jump and a 1.0 jump, and the sizes landing in the 1.0 jumps never get printed by a US entry.

Those European sizes exist and this tool will happily produce them — just not from the men's ladder. Enter 23.5 in Foot length (cm) mode and EU 37.5 comes straight back; enter 42 in EU mode and it returns EU 42.

How to Read Your Result

The panel answers in four lines, and only the first two change with what you typed.

The Four Lines the Panel Prints

For a US Men 10 the output reads exactly like this, headline first and the remaining three as breakdown rows underneath it:

• US M 10 · US W 11.5 · UK 9.5 · EU 43
• Foot length ≈ 27.1 cm (10.7″) on the Brannock scale
• Conversions are the typical brand-chart offsets — individual brands run up to a half size either way
• Best practice: measure your foot in cm and use the brand's own chart when buying

The last two are constant. They are the same sentences for a US Women 6 and for a 34 cm foot, so there is no point reading them for information about your entry — they are the tool telling you, every time, how much confidence the four numbers deserve.

There is no gauge or color band on this calculator; a size has no good or bad zone. Four lines of text is the entire output.

Which of the Four Numbers to Trust

Trust the foot length first. It is the only figure on the panel that corresponds to something physical, and every size shown is derived from it rather than the other way around. Next comes the US men's column, which is the tool's spine — the scale everything is converted into before anything else is computed, and the column that matches the international specification most closely.

The UK and US women's columns are the tool applying a fixed retail offset, and the EU column is a length converted with a fixed allowance and rounded to the nearest half point. Both are reasonable and both are conventions, which is exactly what the third output line is warning you about.

When It Says Check Your Inputs

Two things can stop the calculation, and each produces its own amber notice. A blank, zero, negative or non-numeric entry returns "Enter a shoe size". Anything the scales cannot reach returns "That size is outside the supported range", which is the guard that keeps the tool inside adult sizing.

Every mode is the same window seen through a different scale: the guard is applied on the US men's value, which has to land between 1 and 20. That makes the three English-language rows exact edges, while the last two are converted ones. In centimeters the window opens just above 19.4733 cm and closes at exactly 35.56 cm, so 19.47 is refused while 19.48 goes through, and 35.56 is accepted while 35.57 is not. On the European scale it runs from 31.46 to 55.59, both of them accepted, which is why an entry of EU 31.47 still returns a full result. The half sizes a shopper would actually type — EU 31.5, or a 19.5 cm foot — sit just inside those edges.

Half sizes are a convention here, not a requirement. The Your Size box carries no minimum or maximum attribute and the form is submitted without browser validation, so an entry like 9.3 goes straight through: in US Men mode it returns US M 9.5 · US W 11 · UK 9 · EU 42 on a 26.5 cm foot, every column rounded from the raw value rather than from the rounded one beside it. The formula does the refusing, not the field.

When the Converter Runs

The Your Size box ships empty, so nothing is calculated when the page opens: the result panel waits until you press Calculate. It does not recompute as you type, either — change the size or the system and the old answer stays on screen until the button is pressed again. Reset clears the form and returns the panel to its empty state.

The arithmetic itself runs in your browser: the first press of Calculate fetches a small formula module and evaluates it there, so every answer after that appears without a round trip to a server. Like the rest of the site, the page also loads analytics and advertising tags, which is a separate matter from where the sums happen.

How to Measure Your Foot

A measurement beats a remembered size, because the size you remember came from a brand and the measurement came from you.

The Paper-and-Wall Method

• Put a sheet of paper on hard floor with one short edge against a wall. On carpet both the paper and the foot sink in, which blurs where the heel and the toe actually sit.
• Stand on it with your heel touching the wall and your weight on both feet. Bearing weight is what lets the foot elongate to its full size, so a seated measurement reads short.
• Have someone mark the paper at the tip of your longest toe. On a lot of people that is the second toe, not the big toe.
• Measure from the wall edge to the mark in centimeters and enter that number in Foot length (cm) mode.
• Repeat for the other foot and enter the longer of the two, which is the standard fitting instruction: measure both, fit the larger.

Precision matters more here than it looks. Half a US size is 4.23 mm of foot, so a 2 mm slip in where the pencil lands is worth about a quarter of a size, and a 5 mm slip can move you a full size.

What a Fitter Does Differently

The Brannock Device Company's own fitting instructions add three things a paper-and-pencil measurement misses. The customer should stand "with equal weight on both feet to ensure that the foot being measured has elongated and spread to its maximum size". Socks should be "snug against the toes (without drawing the toes back)". And read the length by looking "straight down over the longest toe (not necessarily the first toe)".

The device also measures arch length — heel to the ball of the foot — and the instructions say to compare it with the heel-to-toe figure and "generally you'll use the larger of the two measurements as the correct shoe size". A long arch with short toes can therefore need a bigger shoe than its overall length suggests. This calculator has one length input and knows nothing about arch length, so if a fitter's device reads longer than your tape, the device wins.

On timing, the same instructions say to have footwear fitted "at a similar time as when you will be wearing the footwear", noting that after a day on your feet they have expanded. Measure in the evening for everyday shoes, and in the morning if you are buying something you will only ever wear first thing.

Width, and What Every Length Chart Leaves Out

None of the four columns on this page says anything about width, and neither does the specification behind them: ISO/TS 19407 states plainly that it does not attempt to assess overall fitting properties — not width, volume or toe depth. Mondopoint is the exception, carrying a linear foot width in millimeters as a secondary figure after the length.

That omission is not academic. Buldt and Menz's 2018 review of footwear fit in the Journal of Foot and Ankle Research reports that in general-population studies between 63% and 72% of participants were wearing shoes that did not accommodate either the width or the length of their feet, and that among the clinical groups reviewed, between 46% and 81% were in footwear too narrow for them. Among older people specifically, the review cites 78% in outdoor shoes narrower than their feet.

The practical reading is that a correct length number can still be the wrong shoe. If a shoe in your calculated size feels tight across the ball of the foot, the answer is a wider fitting rather than a longer one — the review's own recommendation is that more widths be made available at each length.

Limits: Where This Conversion Stops Being Exact

ISO/TS 19407:2015 is unusually candid for a standards document: because the systems were developed and interpreted over many years without being formalized, it says, there is no exact solution to the problem of accurate shoe size conversion. What follows is where this tool's answers sit against that document's own arithmetic.

Checked Against ISO/TS 19407

The specification converts by foot length in millimeters, using a grading interval of 8.47 mm for the English-speaking scales and 6.67 mm for the European one, and it takes the shoe-to-foot difference as two size grades in each system. Its US rule is an offset from the UK scale: one size for men's footwear, usually two for women's.

ISO/TS 19407:2015, foot length in mm

UK       = (foot length + 2 × 8.47) ÷ 8.47 − 25
EUR      = (foot length + 2 × 6.67) ÷ 6.67
US men   = UK + 1
US women = UK + 2

Those are the raw values both methods produce for a 26.0 cm foot, before either is rounded. The US men's agreement is not a coincidence: work ISO's two rules together and its US men's size is the foot length in millimeters divided by 8.47, minus 22 — the same line this calculator draws with three sizes to the inch. The 0.012 gap is entirely the standard rounding a barleycorn to 8.47 mm where the exact third of an inch is 8.4667 mm.

The three offsets hold steady across the whole adult range rather than drifting. At a 22.0 cm foot the differences are +0.010, +0.510, +0.510 and +0.266; at 30.0 cm they are +0.014, +0.514, +0.514 and +0.272. Rounded to halves, the US men's column matched the standard at 79 of the 81 foot lengths from 22.0 cm to 30.0 cm in millimeter steps; the UK and US women's columns matched at none of them.

The UK Column Runs Half a Size Generous

The entire disagreement lives in one constant. This calculator puts UK half a size below US men's; ISO/TS 19407 records the US men's scale as sitting one full size above UK, describing that whole-size offset as what the US system does in practice. Both versions circulate on published size charts, which is why two retailers can differ by exactly half a size on the same conversion — and they cannot both be right about one foot.

The men's row is the clearest illustration of the whole section: the US men's number is identical, the UK number is half a size higher, the European number half a point higher, and the women's number half a size higher. Put the other way round, ISO assigns UK 9 to a 271.0 mm foot while this tool assigns it to a 266.7 mm foot — a gap of 4.3 mm at every size, where half a size is 4.2 mm.

So if you are ordering from a British retailer on a US size, treat the UK figure here as the upper of two candidates and check the seller's own centimeter chart before committing. The European figure carries a smaller version of the same bias: this tool places EU 42 at a 265.0 mm foot where ISO places it at 266.8 mm, which is essentially the 1.66 mm between the 1.5 cm toe allowance added here and the 13.34 mm the standard uses.

Enter EU 42, Get EU 42.5 Back

Conversions here do not always survive a round trip. EU 42 returns US M 9.5. Type that 9.5 into US Men mode and the European column comes back as 42.5, not 42. EU 40 returns US M 7.5, which converts back to EU 39.5; EU 47 returns US M 13, which converts back to EU 46.5. Across EU 36 to EU 47 three sizes behave this way and nine survive intact.

Nothing is malfunctioning. A European entry is turned into a foot length exactly, but the men's size printed from it has been rounded to the nearest half — and a US half size is 0.635 of a Paris point, so the rounded size no longer points back at the length it came from. EU 42 is a 26.5 cm foot; US M 9.5 is a 26.7 cm foot; those 2 mm are the whole discrepancy.

Keep the length rather than the intermediate size and the problem disappears, which is the argument for writing down centimeters instead of a size in the first place.

What the Tool Does Not Cover

Four things sit outside what these four columns can tell you, and one small display artifact is worth knowing about.

• Children's sizes. The floor is US Men 1, US Women 2.5, UK 0.5, EU 31.46, or a foot a hair over 19.4733 cm; below that every mode returns “That size is outside the supported range”. Children's scales are also offset differently — ISO/TS 19407 puts US children about half a size from UK, not the full size it uses for men — so this tool would give the wrong answer for a child even if it accepted the number.
• Width and volume. There is no width input, no letter fitting, and no way to express that a foot is high-arched or broad across the joints.
• Brand lasts. A size names the shape a shoe was built around, and every maker cuts its own. The panel's third line says so on every calculation, and it is the reason the standard itself calls exact conversion impossible.
• Mondopoint labels. The centimeter line is a Mondopoint size in disguise, but the panel never prints an MP or Mondo marking, and no letter width code is produced.
• The inch figure is converted from the rounded centimeter figure rather than the raw one. At US Men 13.5 the panel prints "Foot length ≈ 30.1 cm (11.9″)" where the underlying length, 30.057 cm, is 11.83 inches and would round to 11.8. The gap never exceeds a tenth of an inch and never touches the sizes themselves.

Another everyday measurement that hides three incompatible numbering systems inside one printed label is a tire sidewall, which is decoded in the Tire Size Calculator.

None of this makes the conversion useless. It makes it a starting point: the right shelf, the right half-size pair to try on, and a centimeter figure you can hand to any brand's own chart.