Metric Footwear Guide
Understanding centimeter (CM) and Mondopoint shoe sizing
Centimeter-based shoe sizing specifies footwear sizes using actual foot dimensions rather than arbitrary numbers.
Centimeter-based shoe sizing provides a consistent footwear standard. Formalized by the International Organization for Standardization as the Mondopoint system (ISO 9407:2019), it specifies shoe sizes using actual foot dimensions. While the United States and the United Kingdom rely on historic imperial barleycorn increments, countries like Japan and South Korea base shoe sizing directly on foot length in centimeters or millimeters.
Why UK shoe sizes and centimeters do not convert evenly
Converting between the British (UK) system and centimeters requires rounding. The UK shoe system steps by 1/3 inch (approx. 8.46 mm) per full size and 1/6 inch (approx. 4.23 mm) per half size. Because these imperial fractions do not align with clean decimal numbers, conversions involve slight rounding:
- UK Men's 6 fits a foot length of approximately 24.5 cm (9.6 inches).
- UK Men's 7 fits a foot length of approximately 25.5 cm (10.0 inches).
- UK Men's 8 fits a foot length of approximately 26.5 cm (10.4 inches).
- UK Men's 8.5 fits a foot length of approximately 27.0 cm (10.6 inches).
If your foot measures 27.0 cm, a UK 8.5 provides the recommended fit.
UK child shoe sizes in CM: a parent's guide
The UK children's shoe scale resets mid-childhood. It starts with infant size 0 (approx. 9.5 cm) and runs through child size 13.5 (approx. 20.5 cm), after which adult sizing begins again at size 1 (approx. 21.0 cm):
- UK Child 3 to 4 fits toddler feet measuring 11.5 to 12.5 cm.
- UK Child 6 to 7 fits toddler feet measuring 14.2 to 15.0 cm.
- UK Child 9 to 10 fits children with feet measuring 16.7 to 17.5 cm.
- UK Child 12 to 13 fits children with feet measuring 19.2 to 20.0 cm.
When shopping for growing kids, measure their feet every 8 to 12 weeks. Always choose a shoe size that provides 10 to 12 mm of space in front of the longest toe.
How to use the CM tongue tag when buying sneakers
When buying athletic sneakers from brands like Nike, Adidas, Asics, and New Balance, note that US-to-EU charts can differ. For example, a Nike US 9 is labeled as EU 42.5 on shoe tags, whereas standard ISO 19407 maps US 9 to EU 42.
Look at the JP or CM measurement printed on the inner tongue label. A 27.0 CM shoe provides consistent length across almost every brand worldwide.
A 27.0 cm foot fits comfortably in a 27.0 CM shoe across athletic brands, regardless of how the manufacturer translates that size into US or European figures.
Measuring foot width in centimeters
Foot length is only half of the sizing calculation. Foot width is measured across the first and fifth metatarsal joints (the ball of the foot). For an adult foot measuring 26.0 cm in length, a standard medium width (D width for men, B width for women) measures between 9.5 and 10.0 cm flat across the ball. If your measurement exceeds 10.4 cm, you will likely find standard footwear tight across the sides, and should look for wide (2E) or extra-wide (4E) options rather than simply buying a longer shoe.