Why Foot Gauge Numbers Aren't Millimetres
Foot gauge scales look like millimetres but aren't. Learn why that matters and how to enter the numbers correctly.
Parents ask us this more than anything else: “My gauge says 150. Is that 150 mm?” No.
Gauges use their own scale
A children’s foot gauge turns a foot into a shoe size and a width fitting. Its makers spaced the numbers to match that sizing system, so they don’t follow a ruler. The length scale on many gauges runs from 97 to 281, and the width scale from 67 to 227.
A ruler gives you a different number for the same foot. Convert that number yourself and you’ll land on the wrong size.
How to enter the numbers
Enter them exactly as printed. Don’t add or subtract anything, convert to centimetres or round to the nearest ten. The calculator works on the gauge’s own scales.
Without a gauge
You can estimate a size from foot length in centimetres with our kids’ size chart. It shows the approximate foot length each UK size fits. The chart can’t give you a width fitting. A gauge or a trained fitter can.
Why the calculator checks your numbers
The scales have fixed ranges, so the calculator warns you about a number outside them (“Enter a number between 97-281”). It checks the pair too. A width as big as the length, such as 123 × 123, matches no real foot, so you’ll see No size found and a prompt to measure again.
