Choose a wearer group to convert a known shoe size or measured foot length into an approximate US, UK, or EU size.
Table of contents
How to use our Shoe Size Conversion Calculator
- Choose whether you are starting with a known shoe size or a measurement of the longer foot.
- Select the wearer size group shown on the shoe label, store listing, or chart.
- For a known size, choose its printed system and enter the size; for a measurement, enter heel-to-longest-toe length and choose inches or centimeters.
- Choose the system you need under Convert to, then select Calculate.
- Use the converted size as a starting point. Check that the matched chart foot length is close to your measurement, then check the target brand's size chart before buying.
Definitions
Wearer size group: The men's, women's, or child scale used for the shoe. The same number can match different rows in different groups.
Known size system: The regional system attached to the size you already know: US, UK, or EU.
Foot length: The distance from heel to longest toe on the longer foot, measured while standing. It is not the same as a CM or Mondopoint marking printed on a shoe.
Approximate converted shoe size: The size in the destination system on the calculator's matched chart row. It is not a brand-specific fit promise.
Matched chart foot length: The foot-length reference in centimeters assigned to the selected chart row.
Inch-to-centimeter conversion: One inch equals exactly 2.54 centimeters.
Common mistakes and quick fixes
Mistake: Using a women's, men's, or child group that does not match the original shoe label.
Fix: Check What are you starting with? and then recalculate. Choose the same wearer size group shown by the shoe, listing, or source chart.
Mistake: Entering a size number without identifying whether it is US, UK, or EU.
Fix: Set Known size system to the system printed beside the known size.
Mistake: Entering a size such as 9.3.
Fix: Check What are you starting with? and then recalculate. Enter a whole or half size only, such as 9 or 9.5.
Mistake: Entering centimeters while Foot-length unit is set to Inches.
Fix: Choose the unit used by your ruler or tape measure before entering foot length.
Mistake: Treating the converted size as a guaranteed fit.
Fix: Check What are you starting with? and then recalculate. Check the target brand's chart, width guidance, and shoe-style notes before ordering.
Limitations & Key Assumptions / Boundary Conditions
- This calculator uses an approximate internal crosswalk, not an official universal sizing standard or a brand-specific chart.
- Brand, shoe style, width, material, socks, and personal fit preference can change the best size.
- Only supported whole and half-size chart rows can be converted. Values outside the selected wearer group's chart are rejected.
- Foot-length results need a heel-to-longest-toe measurement of the longer foot while standing. A shoe's CM or Mondopoint marking is a different measurement.
- Foot-length matches are rounded to the nearest half-step chart row. An exact midpoint is assigned to the larger half-step row.
Methodology
Calculation method
For a known shoe label, the calculator changes the entered US, UK, or EU size into a shared chart row for the selected wearer group. It then changes that row into the system selected under Convert to.
row_index_raw = known_size (US), known_size + group_uk_offset (UK), or known_size - group_eu_offset (EU)
For measured foot length, an inch value is first converted to centimeters. One inch equals 2.54 centimeters.
foot_length_cm = foot_length (cm) or foot_length * 2.54 (inches)
row_index_raw = (foot_length_cm - group_foot_intercept_cm) / group_foot_step_cm
The raw chart position is rounded to the nearest half-step. If it is exactly between two half-steps, the larger row is selected.
selected_row_index = floor(row_index_raw * 2 + 0.5) / 2
converted_size = selected_row_index (US), selected_row_index - group_uk_offset (UK), or selected_row_index + group_eu_offset (EU)
matched_chart_foot_length_cm = round((group_foot_intercept_cm + selected_row_index * group_foot_step_cm) * 10) / 10
Worked example
For a men's US 9 converted to EU, the shared row is 9. Adding the men's EU offset of 33 gives EU 42. The matched chart foot length is 20 + (9 * 0.6666666666666667), which is 26.0 cm.