Shoe Size Converter
Convert shoe sizes between UK, US, EU and centimetres by working through foot length, the only measurement all the systems agree on.
How to use this calculator
- 1Pick the system you already know your size in and enter it.
- 2Read the foot length — that is the objective figure, and the one to trust.
- 3Use the other systems as a starting point, then check the specific brand's own chart.
How the calculation works
UK = 3 × foot(in) − 23 US men = UK + 1 US women = UK + 2 EU = 1.5 × (foot(cm) + 1.5)- barleycorn
- 1/3 inch, 8.467 mm — the step between UK and US sizes
- Paris point
- 2/3 cm, 6.667 mm — the step between EU sizes
- foot(cm) + 1.5
- EU sizes measure the shoe last, which is about 1.5 cm longer than the foot to leave toe room
All conversions route through foot length rather than chaining offsets between systems, because each system is a different linear function of length and chaining compounds the rounding.
The step sizes are incommensurable: a barleycorn is 8.467 mm and a Paris point 6.667 mm, so EU sizes climb about 1.27 times faster. There is no exact whole-number correspondence, only a nearest match.
UK sizing nominally starts at size 0 for a four-inch last, which is why the formula subtracts 23 — the constant that anchors the scale.
EU sizing measures the last rather than the foot, which is why an allowance is added. That allowance is not standardised, so EU conversions vary more between brands than UK or US ones.
Worked example
A UK size 8
- 1.UK sizes step by one barleycorn — a third of an inch — from a size 0 at four inches.
- 2.Foot length: (8 + 23) ÷ 3 = 10.33 inches = 26.2 cm.
- 3.US men's is one size above UK: 9.
- 4.US women's is two above: 10.
- 5.EU measures the last, about 1.5 cm longer than the foot: 1.5 × (26.2 + 1.5) = 41.6, so around EU 42.
- 6.Note the EU figure is not a round number — the systems do not align exactly.
Result: UK 8 ≈ US men 9, EU 42, foot 26.2 cm
Working from a measured foot
- 1.A measured foot length of 24 cm is 9.45 inches.
- 2.UK: 3 × 9.45 − 23 = 28.35 − 23 = 5.35, so about UK 5.5.
- 3.US men's: 6.35, so about 6.5. US women's: 7.35, so about 7.5.
- 4.EU: 1.5 × (24 + 1.5) = 38.25, so about EU 38.
- 5.Measuring the foot is far more reliable than converting between systems, because it skips every accumulated rounding.
Result: UK 5.5, US women 7.5, EU 38
Two incompatible units, 700 years apart
English shoe sizes step by a barleycorn — one third of an inch. The unit is genuinely medieval: the standard is usually traced to Edward II, who in 1324 defined the inch as three barleycorns laid end to end. Shoemakers adopted the barleycorn as their size increment and it has not changed since.
Continental Europe uses the Paris point, two thirds of a centimetre, which arrived with metrication and is smaller. The consequence is that EU sizes climb about 1.27 times faster than UK ones, and half sizes are correspondingly rarer because a full Paris point is already a small step.
Because 8.467 mm and 6.667 mm have no common multiple, no exact conversion exists between the systems. Every published chart is a rounding, which is why two charts will happily disagree by half a size on the same conversion. Working through foot length at least makes the rounding explicit.
Why the converted number is only a starting point
Length is the only dimension these systems describe, and it is not the only dimension that matters. Width, instep height, heel volume and toe box shape all vary enormously between manufacturers, and a shoe that is the right length can still be unwearable.
Brand variation in length alone routinely reaches a full size. Anyone who wears several brands knows they are not the same number in each, and there is no standards body enforcing consistency — the size on the box is the manufacturer's claim, not a measurement.
Feet also change through the day, swelling by up to half a size by evening, and most people have one foot slightly larger than the other. Fit the larger foot, measure in the afternoon while standing so the foot is under load, and wear the socks you actually intend to use. These are the fitter's rules and they beat any conversion chart.
What this assumes, and where it stops
Assumptions
- UK sizing follows the barleycorn scale anchored at a four-inch last for size 0.
- US men's sizes run one above UK, and US women's two above, which is the most widely used convention.
- EU sizing measures the shoe last in Paris points, with about 1.5 cm of allowance over the foot.
- Results are rounded to the nearest half size, as shoes are sold.
Limitations
- Conversions are approximate by nature. The UK/US and EU systems use incommensurable step sizes, so no exact correspondence exists and published charts routinely disagree by half a size.
- Brand variation of up to a full size is common and is not modelled — no standards body enforces consistency.
- Length only. Width fittings, instep and toe shape matter as much for fit and are not captured by any of these numbers.
- Adult sizing only. Children's scales use different anchors and are not covered.
- The EU last allowance is not standardised, so EU results carry more uncertainty than UK or US ones.
Common questions
How do I convert UK shoe size to EU?
There is no exact rule, because the systems use different step sizes — a barleycorn of 8.467 mm against a Paris point of 6.667 mm. Roughly, EU is about UK plus 33, so UK 8 is around EU 42. Converting through foot length gives a better answer than any fixed offset.
What is the difference between US men's and women's shoe sizes?
For the same foot length, a US women's size is about one and a half sizes above the men's number — a women's 9 and a men's 7.5 fit roughly the same foot. UK sizing is nominally unisex, so a UK number means the same length for anyone.
How do I measure my foot for shoe size?
Stand on paper with your weight on the foot, mark the heel and the longest toe, and measure between them. Do it in the afternoon, when feet have swollen slightly, and measure both feet — most people have one larger, and you should fit the larger one.
Why are shoe sizes so inconsistent between brands?
Because no standards body enforces them. The number on the box reflects the manufacturer's last, and lasts differ in length, width and shape. Variation of a full size between brands is common, which is why the measured foot length is the only figure worth treating as objective.
Sources
Formula and content last reviewed on .
Results are estimates for information only, not professional advice.
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