How this instrument works
European shoe sizes are built on the Paris point system: each size step represents 2/3 of a centimetre of internal shoe length, anchored so that the size number relates directly to a foot-length measurement in centimetres. That relationship can be inverted — given an EU size, back out the foot length it implies — which is exactly the first step this calculator performs.
From that implied foot length, the calculator converts to inches and applies the traditional US sizing formula: foot length in inches, times three, minus 22 for men's sizing or minus 21 for women's. This mirrors the same 'three sizes per inch' step used across US shoe charts (a size step equals roughly a third of an inch), just anchored differently for the two sizing conventions, which is why the same EU size produces a different US number depending on which gender scale you pick.
This is a companion piece to a US-native, Brannock-anchored size calculator elsewhere on this site — that one starts from a directly measured foot length and works out a US size plus a constant-offset EU estimate; this one starts from an EU label and derives foot length first. Both are honest approximations of a genuinely messy reality: real brand lasts vary, and a size that's 'correct' by the math can still fit differently between manufacturers.
- Enter the EU size shown on the shoe's label or box.
- Choose men's or women's sizing — the two scales use different constants and will return different US sizes for the same EU number.
- Read the implied foot length in centimetres, calculated from the EU size.
- Read the approximate US size.
Worked example — a men's EU 42 shoe
EU 42, men's sizing: foot length = (42 − 2) ÷ 1.5 = 26.667 cm. Converting to inches: 26.667 ÷ 2.54 = 10.499 in. Applying the men's formula: 10.499 × 3 − 22 = 9.496 — an EU 42 corresponds to roughly a US men's size 9.5.
Swap to women's sizing at a smaller EU 38 and the math runs the same way but lands differently: foot length = (38 − 2) ÷ 1.5 = 24 cm = 9.449 in; US size = 9.449 × 3 − 21 = 7.346, or roughly a US women's 7.3 — illustrating why the gender selector matters even before you change the EU size itself.
Questions
Why is the subtraction different for men's (22) versus women's (21) sizing?
The two constants anchor the same underlying foot-length-to-size relationship to two different reference scales, since US men's and women's shoe sizing use offset numbering even for an identical foot length — a US women's size is conventionally about 1.5 to 2 sizes higher than the men's size for the same foot. The different subtraction constants (22 vs 21) reproduce that offset when converting from the EU scale.
Is this the exact method every shoe brand uses?
No single formula is universal — this calculator applies the standard, widely quoted Paris-point-based conversion, but individual brands cut their lasts (the foot-shaped mold a shoe is built on) slightly differently, so real-world fit can drift from the formula's prediction, especially for athletic or specialty shoes with their own sizing quirks.
How does EU shoe sizing (the Paris point system) actually work?
Each EU size step equals 2/3 of a centimetre (about 6.7 mm) of internal shoe length, so the size number scales roughly linearly with foot length in centimetres. That's a different anchor system entirely from the US scale's third-of-an-inch step size, which is why converting between the two needs an actual formula rather than a simple offset.
Why might my actual US size differ from what this calculator shows?
Foot width, arch height, and brand-specific last shape all affect real-world fit in ways a length-based formula can't capture, and the underlying EU-to-US math itself is an approximation rather than a precise, universally standardized conversion. Use this as a strong starting point for narrowing down a size to try on, not a guaranteed match.
Does this work for children's shoe sizes?
No — this calculator is built for adult men's and women's sizing. Children's shoe sizing uses its own separate numbering scale (often restarting near size 13.5 for toddlers before continuing into youth sizes), so plugging a children's EU size into this adult-scaled formula will give a meaningless result.