Children’s feet grow fast and the sizes are confusing: 10C, 2Y, EU 27, UK 9.5. A shoe that is too small cramps growing toes, and one that is too large causes trips. This calculator turns the length of your child’s longer foot into the US kids’ size and shows the UK, European and centimetre sizes that go with it.
How to use the kids shoe size calculator
- Measure the foot. Stand your child on a sheet of paper with the heel against a wall, mark the tip of the longest toe, and measure from wall to mark.
- Measure both feet and use the longer one.
- Enter the length in centimetres or inches.
- Read the size. It shows the US kids’ size (1C to 13.5C and 1Y to 7Y), the UK and EU sizes, and the foot length the size is made for. Allow a little growing room in the shop.
Kids shoe size formula and chart
quick check: US kids size ≈ 3 × foot length (in) − 9¾
The chart is Nike’s kids’ footwear table (retrieved 2026-10-15), which lists foot length in sixteenths of an inch. Wikipedia’s Shoe size page gives the standard formula for children’s sizes, child size = 3 × last length (in) − 11¾, or about 3 × foot length (in) − 9¾ for the foot itself, which is shown as a cross-check. The centimetre column is the inch value × 2.54.
| US kids size | Foot length (in) | Foot length (cm) | UK | EU | CM/JP |
|---|---|---|---|---|---|
| 1C | 3 9/16 | 9.0 | 0.5 | 16 | 7 |
| 2C | 3 15/16 | 10.0 | 1.5 | 17 | 8 |
| 3C | 4 4/16 | 10.8 | 2.5 | 18.5 | 9 |
| 4C | 4 9/16 | 11.6 | 3.5 | 19.5 | 10 |
| 5C | 4 15/16 | 12.5 | 4.5 | 21 | 11 |
| 6C | 5 4/16 | 13.3 | 5.5 | 22 | 12 |
| 7C | 5 9/16 | 14.1 | 6.5 | 23.5 | 13 |
| 8C | 5 15/16 | 15.1 | 7.5 | 25 | 14 |
| 9C | 6 4/16 | 15.9 | 8.5 | 26 | 15 |
| 10C | 6 9/16 | 16.7 | 9.5 | 27 | 16 |
| 10.5C | 6 12/16 | 17.1 | 10 | 27.5 | 16.5 |
| 11C | 6 15/16 | 17.6 | 10.5 | 28 | 17 |
| 11.5C | 7 1/16 | 17.9 | 11 | 28.5 | 17.5 |
| 12C | 7 4/16 | 18.4 | 11.5 | 29.5 | 18 |
| 12.5C | 7 7/16 | 18.9 | 12 | 30 | 18.5 |
| 13C | 7 9/16 | 19.2 | 12.5 | 31 | 19 |
| 13.5C | 7 12/16 | 19.7 | 13 | 31.5 | 19.5 |
| 1Y | 7 15/16 | 20.2 | 13.5 | 32 | 20 |
| 1.5Y | 8 1/16 | 20.5 | 1 | 33 | 20.5 |
| 2Y | 8 4/16 | 21.0 | 1.5 | 33.5 | 21 |
| 2.5Y | 8 7/16 | 21.4 | 2 | 34 | 21.5 |
| 3Y | 8 9/16 | 21.7 | 2.5 | 35 | 22 |
| 3.5Y | 8 12/16 | 22.2 | 3 | 35.5 | 22.5 |
| 4Y | 8 13/16 | 22.4 | 3.5 | 36 | 23 |
| 4.5Y | 8 15/16 | 22.7 | 4 | 36.5 | 23.5 |
| 5Y | 9 2/16 | 23.2 | 4.5 | 37.5 | 23.5 |
| 5.5Y | 9 4/16 | 23.5 | 5 | 38 | 24 |
| 6Y | 9 6/16 | 23.8 | 5.5 | 38.5 | 24 |
| 6.5Y | 9 9/16 | 24.3 | 6 | 39 | 24.5 |
| 7Y | 9 11/16 | 24.6 | — | 40 | 25 |
Nike prints the UK number 6 for both 6.5Y and 7Y, which looks like a repeat, so the UK size of 7Y is left blank here.
Worked example
A child’s longer foot measures 15.5 cm.
- 15.5 ÷ 2.54 = 6.10 in.
- Size 9C is made for 6 4/16 in (6.25 in), which is longer than the foot, and 8C for 5 15/16 in (5.94 in), which is shorter. The first size whose length is at least 6.10 in is 9C.
- UK 8.5, EU 26.
- Cross-check: 3 × 6.10 − 9.75 = 8.6, which points to the same size range (a little below 9).
Fitting tips
- Measure in the afternoon, when feet are slightly larger.
- Check room: there should be about a thumb’s width between the longest toe and the end of the shoe.
- Width matters: a narrow or wide foot may need a different width, which this calculator does not cover.
- Socks: measure and try shoes on with the socks your child will wear.
The sizes are for Nike’s lasts; other makers differ by half a size or more, so also check each maker’s chart. For adult sizes see the Shoe Size Calculator (foot length), and for conversion between countries the Shoe Size Converter (US/UK/EU/JP). This page offers general guidance only.
Sources
Every figure above comes from these pages, read directly on the dates shown. Brand names are used only to identify the published charts.
- Nike — kids’ shoes size chart (foot length, US kids, UK, EU, cm/JP) — checked 2026-10-15
- Wikipedia — Shoe size (children’s size formula) — checked 2026-10-15
Frequently asked questions
How do I measure my child’s foot?
Have the child stand with a heel against a wall on a sheet of paper. Mark the longest toe and measure from the wall to the mark. Do both feet and use the longer one, as Nike advises.
What if my child is between two sizes?
Size up. Nike’s guide says that if you are between sizes you should go up. The calculator rounds a foot up to the next chart size for this reason, then you can add a thumb’s width of room in the shop.
What do C and Y mean in kids’ sizes?
C stands for children’s sizes (1C to 13.5C, up to about age 7) and Y for youth sizes (1Y to 7Y). After 7Y the child moves to adult sizes, where a youth 7Y is similar to an adult men’s 7.
How accurate is the 3 × foot − 9¾ rule?
It comes from the formula for children’s sizes on the Wikipedia Shoe size page and works well for small sizes, but drifts above size 10 or so. Use the chart value for ordering and the formula only as a quick check.
Do kids grow out of shoes quickly?
Young children can need a new size every few months. Re-measure often, and see the Baby Clothes Size Calculator for clothes. Check the shoe is not tight after each growth spurt.