Methodology
Every chart on this site starts from one physical measurement and ends in a printed label. This page documents what that measurement is per category, how it is rounded into the label, which published standard fixes it, and where no standard exists at all. It also records the conversions where published sources genuinely disagree and which side this site takes.
The one rule everything follows
A size label is a name for a body measurement. It is never a measurement itself. That single distinction explains almost every confusing thing about international sizing: two systems can name the same body differently, the same name can cover a range rather than a point, and a system can have a half size where another has none. Every table on this site is therefore built the same way. Take the physical anchor, apply the published rounding rule for each system, print the label. The anchor column stays in the table so you can always fall back to it when a retailer's chart contradicts this one.
Rounding, shown rather than claimed
Ring sizes are circumference, rounded
The EU/ISO ring number is the inner circumference of the band in millimetres, rounded to a whole number. That is not a rule of thumb, it is what ISO 8653 fixes, and it is visible in the data: the printed EU number and the measured circumference differ by less than half a millimetre everywhere, and the difference is not constant.
| EU/ISO number | Measured circumference (mm) | Rounding difference (mm) |
|---|---|---|
| 44 | 44.2 | -0.2 |
| 52 | 51.9 | 0.1 |
| 59 | 59.5 | -0.5 |
| 67 | 67.2 | -0.2 |
This is the sort of thing most sizing pages leave implicit. It matters because it tells you what to do at a boundary: if your measured circumference is 52.5 mm, the chart will hand you one number, but you are genuinely between two sizes and the band width of the ring will decide which one fits.
Shoe sizes do not step evenly
Shoe sizes are anchored to foot length in centimetres, which ISO 9407 formalises as the Mondopoint system. The EU scale derives from Paris points of two thirds of a centimetre, and the printed half sizes do not divide that evenly. Across the adult chart on this site the step between neighbouring EU sizes takes the values 0.4, 0.5, 0.8, 0.9 centimetres. There is no single step size to quote, which is exactly why every size page here states the step to its own neighbours instead of repeating an average.
The practical consequence: a foot that sits between two rows is not evenly between two sizes. Going up half a size can buy you 0.4 cm in one part of the range and 0.5 cm in another.
Per category: anchor, rounding and standard
Ring sizes
Anchor. The inner circumference of the ring in millimetres.
Rounding. The EU/ISO column is that circumference rounded to the nearest whole millimetre, which is why EU 44 sits at 44.2 mm, EU 53 at 53.1 mm and EU 69 at 69.7 mm. The rounding error is never more than half a millimetre and it is not constant across the scale.
Standard. ISO 8653 fixes the definition, measurement and designation of ring sizes, expressed as the inner circumference in millimetres, which gives the EU/ISO column, and through it the diameter and circumference columns.
Shoe sizes
Anchor. The length of the foot in centimetres.
Rounding. Every row describes one foot length. The steps between neighbouring EU sizes are not equal: EU 38 to 38.5 is 0.4 cm while EU 39 to 40 is 0.5 cm, because the EU scale is built on Paris points of two thirds of a centimetre and then printed as whole and half numbers.
Standard. ISO 9407 fixes the Mondopoint system, which labels a shoe by the foot length it is built for, in millimetres, optionally with the foot width, which gives the foot length column, which every other column is derived from.
Not standardised. The US and UK numbers are not covered by any international standard. Both descend from the barleycorn, a third of an inch, and the two scales are offset from each other by conventions that published charts genuinely disagree about. This chart puts the US men's number half a size above the UK number; other charts put it a full size above. Both agree on the foot length, so when a retailer's chart contradicts this one, go by centimetres.
Bra sizes
Anchor. Two body measurements in centimetres or inches: the underbust, which sets the band, and the fullest part of the bust, which together with the band sets the cup.
Rounding. The cup letter follows from the difference between bust and underbust, roughly one inch per cup step. Because that difference is rounded twice, once into inches and once into a letter, a measurement close to a boundary can land a size either way.
Standard. ISO 8559-1 fixes where and how the underbust and bust measurements are taken, which gives the underbust and bust columns that the band and cup are read from.
Not standardised. There is no international standard for bra sizes themselves. The band and cup systems used in the US, UK, EU, France, Italy and Australia are separate conventions that were never harmonised, and brands vary within each of them. Treat every row here as a starting point and check a brand fit before you buy.
Hat sizes
Anchor. The circumference of the head in centimetres.
Rounding. The EU number is the head circumference in whole centimetres. The US and UK fitted numbers are eighths of an inch of head diameter, which is the circumference divided by pi, which is why they come out as fractions like 7 1/8 rather than round numbers.
Standard. None that we know of.
Not standardised. We know of no published international standard for hat sizes. Every column here is a convention derived from head circumference, which is why the circumference column is the one to trust.
Clothing sizes
Anchor. Body measurements in centimetres, chiefly bust or chest, waist and hip.
Rounding. Letter sizes and numeric sizes are both labels for a range of body measurements, not for a single value, so two brands can label the same body differently and both be defensible.
Standard. ISO 8559-1 fixes the anthropometric definitions for body measurement: where on the body each measurement is taken and how, which gives the bust, chest, waist and neck columns. EN 13402 fixes how clothing sizes are designated in Europe from body dimensions in centimetres, including the pictogram labelling, which gives the EU column and the body-measurement columns beside it.
Not standardised. There is no legally binding clothing size standard anywhere. EN 13402 describes how to designate a size from body measurements, but no law requires a brand to use it, and most do not. Every clothing conversion on this site, including this one, is therefore a mapping between conventions and not between fixed values. Always check the brand's own body-measurement table.
Glove sizes
Anchor. The circumference of the hand around the knuckles, excluding the thumb.
Rounding. The numeric glove size is that circumference in inches, rounded to the nearest half size. The letter size groups two numeric sizes together.
Standard. None that we know of.
Not standardised. For fashion and general-purpose gloves there is no binding standard. The inch-based numeric size is a widely shared convention rather than a specification.
Belt sizes
Anchor. The waist measurement where the belt is actually worn, in inches or centimetres.
Rounding. A belt is normally labelled about two inches (five centimetres) above the trouser waist, so the buckle lands near the middle hole. That offset is a convention, not a rule, and some brands label by total belt length instead.
Standard. None that we know of.
Not standardised. We know of no published standard for belt sizes. Measure an existing belt from the buckle fold to the hole you use and compare that length, which is the only reading that is not brand dependent.
Sock sizes
Anchor. The length of the foot in centimetres, the same anchor as shoe sizes.
Rounding. Sock sizes cover ranges rather than points, so a foot at the edge of a range fits either the smaller or the larger size depending on how much the knit stretches.
Standard. None that we know of.
Not standardised. We know of no published standard for sock sizes. The numeric sock sizes still printed on some packaging (9 to 11, 10 to 13) are shoe-size ranges in the US men's scale, which is why this chart maps them straight back to shoe size.
Known disagreements between sources
Anywhere published charts contradict each other, this site picks a side and says so. Two such cases have been recorded so far, both corrected on 25 July 2026 and both in the changelog.
The UK to US shoe offset
Some published charts put the US men's number half a size above the UK number, others put it a full size above. This site uses the half-size offset. Both conventions agree on the foot length, and they never differ by more than half a size, so the safe reading in a dispute is the centimetre column. If a retailer publishes a chart that contradicts this one, go by foot length and you will be right under either convention.
The sock medium range
Sock size ranges are printed differently by different manufacturers, and the medium range is the one that moves most. This site maps sock sizes straight back to shoe size ranges anchored in foot length, rather than to another manufacturer's letter, because that is the only reading that does not depend on whose packaging you are holding.
What this site will not do
- Publish a conversion it cannot anchor to a physical measurement. If there is no anchor, there is no row.
- Copy a brand's size table. Brand tables are theirs, they change without notice, and reproducing one turns an error of theirs into an error of ours.
- Round a value silently. Where rounding changes the answer, the page says so.
- Claim a standard exists where none does. For hats, belts, socks and bras the answer is that no international standard is known, and that is stated on those pages.
Corrections
MySizeCharts is maintained by Jamey Weber. A correction is checked against the physical anchor and the standard for that category before it is applied, never against another website. If it holds, it is applied and dated in the changelog. If it does not, you get an answer explaining why. Send a correction: it is the most useful thing anyone can send this project.
Common questions
Why do two size charts sometimes disagree?
Because most size labels are conventions, not standards. Only a few of them, ring sizes and shoe foot length among them, are fixed by a published standard. The rest are traditions that different sources rounded differently, so two honest charts can differ by half a size and both be defensible. Where that happens this site says which convention it uses and why.
Why does a size exist in one system but not another?
Because the systems do not step at the same interval. EU shoe sizes step in about two thirds of a centimetre, UK and US sizes in a third of an inch, so the two grids only line up occasionally. A half size in one system can land between two sizes in another, which is why every chart here also gives the physical measurement.
How are the numbers rounded?
Every column is derived from one physical measurement and then rounded to whatever precision that system prints. The rounding is documented per category on this page. Where the rounding pushes a value close to a boundary, the chart page says so rather than pretending the answer is exact.
What happens when someone reports an error?
It is checked against the physical anchor and the published standard for that category, not against another website. If the correction holds it is applied and recorded in the changelog with a date. Two corrections have been made this way so far, both on 25 July 2026.
Last reviewed and updated on August 5, 2026. Conversion tables are checked against published international sizing standards.