{{ summaryTitle }} {{ summaryValue }} {{ summaryLine }}
Use a foot measurement when possible; changing source type loads its matching example.
{{ sourceInputHelp }}
{{ sourceInputSuffix }}
Regional inputs keep their own label in the headline; this preference applies to direct foot measurements.
The 1.5 cm default is a comparison baseline, not a fit prescription for every shoe.
Use the seller's available sizes and compare the rounding-drift chart before ordering.
{{ workflowFeedback }}
Optional examples: B, D, 2E, Wide, or Narrow.
Regional labels still follow their own retail increments.
Applied to US men, US women, and UK outputs.
The Brazil estimate uses its own step below.
Use 0.5 cm for the default comparison.
cm
Use 5 mm for the default comparison.
mm
Use 5 mm for the default comparison.
mm
Use 1 for whole Brazil labels unless the seller chart says otherwise.
Keep 0 for the normal EU minus two estimate.
SystemConverted labelMeasurement basisCopy
{{ row.system }}{{ row.value }}{{ row.basis }}

How to use this comparison

{{ note.title }}

{{ note.text }}

Reference context: ISO 19407:2023 treats foot length as the conversion anchor and the conversion tables as consumer guidance. The last-length algebra here is an approximate comparison model; confirm the seller's current chart and physical fit.

Ring Size Converter Convert ring diameter or circumference into matched regional sizes with nearby-row deltas, sold-size increments, and practical fit guidance.
Unit Converter Convert measurements across 21 categories with auditable base-unit formulas, flexible precision, and checks for temperature and fuel economy.
Body Metrics Calculator Compare adult BMI and waist ratios with three body-fat estimates, derived fat and lean mass plus BSA and method-spread warnings.
Ideal Weight Calculator Compare four classic ideal-weight formulas by adult height, then place their spread beside a BMI corridor and optional current-weight context.

Shoe sizes are labels from several measurement traditions, not universal dimensions. The same foot can receive a US men's number, a different US women's number, a UK or EU size, and centimetre- or millimetre-based labels in Japan, China, Korea, or Mexico. A conversion is most dependable when all of those labels are traced back to heel-to-toe foot length.

Two lengths matter. Foot length is the body measurement from the back of the heel to the longest toe. Last length is an estimated interior length after adding space for movement and toes. US, UK, EU, and the Brazil estimate are derived from that longer value here, while JP, MX, CN, and KR stay anchored to foot length.

Scale familyComparison basisImportant caution
US men's, US women's, UKEstimated last length in inchesThe starting offsets differ, and retail half sizes add rounding.
EU and Brazil estimateEstimated last length in centimetresBrazil uses an adjustable offset and brand charts vary.
JP and MXFoot length in centimetresA seller may use its own label increments or fit allowance.
CN and KRFoot length in millimetres26 cm and 260 mm are equivalent; a missing zero changes the result drastically.

Length alone does not determine fit. Width, toe-box shape, upper material, socks, intended activity, and the difference between the two feet can all change the best choice. A width label such as D or 2E is meaningful only within the brand and scale that defines it; it does not modify a length conversion by itself.

Measure both feet while standing, preferably later in the day, and use the longer measurement. Then compare the result with the seller's chart for the exact model. International conversion tables are guidelines because sizing systems developed differently and brands interpret them through their own lasts and retail ranges.

How to Use This Tool:

Begin with foot length when it is available; a regional label must first be converted back to an estimated foot length.

  1. Choose Starting value and enter one foot measurement or regional size. Check centimetres against millimetres before continuing.
  2. For a direct foot measurement, choose the Primary US scale. Regional-label inputs keep their own scale as the primary result.
  3. Set Fit allowance. The 1.5 cm default is a comparison baseline, not a prescription for every shoe or activity.
  4. Choose Retail rounding and, under Advanced, match each step to the sizes the seller offers. Add a width note only as a reminder; it does not change the calculations.
  5. Compare the Size matrix with the Rounding drift chart and Fit guidance. Confirm the selected label on the brand's chart before ordering.

Interpreting Results:

The primary size is the selected retail label after rounding. The effective allowance is the interior-length room implied by that rounded primary label, so it can differ slightly from the configured allowance.

StatusEffective allowanceReading
TightBelow 0.8 cmThe rounded primary size leaves little modeled length allowance.
Balanced0.8 through 1.6 cm inclusiveThe rounded result stays within the central comparison band.
RoomyAbove 1.6 cmThe rounded primary size adds more modeled length allowance.

Drift values are the difference between each rounded label's implied length and its target length. A positive value means the rounded label runs longer than the unrounded target; a negative value means shorter. Small drift does not prove good fit because width and shoe shape are outside the model.

Technical Details:

The calculation uses a foot-length anchor and a repository-authored last-length approximation. It does not reproduce the official ISO conversion tables. A direct measurement is normalized to centimetres; a regional label is inverted through the same formulas to estimate foot length, using the selected allowance and Brazil adjustment where applicable.

Formula Core

First, configured allowance is added to foot length:

L=F+A

F is foot length in centimetres, A is the allowance in centimetres, and L is estimated last length in centimetres. The main label formulas are then rounded to the configured retail step:

SUS,M=Rs(3L2.54-24) SUS,W=Rs(3L2.54-23) SUK=Rs(3L2.54-25) SEU=Rs(1.5L) SBR=Rs(1.5L-2+O) SJP/MX=Rs(F) SCN/KR=Rs(10F)

Rs rounds to step s using nearest, lower, or higher mode. O is the adjustable Brazil offset. US and UK formulas divide centimetres by 2.54 to work in inches; CN and KR multiply centimetres by 10 to produce millimetres.

For a 26.0 cm foot with a 1.5 cm allowance, L is 27.5 cm. With nearest rounding to the default steps, the results are US men's 8.5, US women's 9.5, UK 7.5, EU 41.5, BR 39, JP 26.0 cm, MX 26.0 cm, CN 260 mm, and KR 260 mm. The rounded US men's label implies about 1.52 cm of allowance, which is classified as balanced.

Reverse conversion and bounds

A regional starting label is inverted before the forward conversions run. For example, EU size E resolves to F = E / 1.5 - A. US men's, US women's, and UK inputs reverse their corresponding inch formulas; JP, MX, CN, and KR labels already express the foot-length anchor. This round trip is internally consistent, but it remains an approximation rather than a brand-specific fit model.

  • Resolved foot length must be from 10 through 40 cm inclusive. Values from 18 through 31 cm inclusive are marked as the typical adult range; that status does not change the conversion.
  • Allowance accepts 0 through 5 cm. Retail steps accept 0.1 through 2 for US/UK, EU, and JP/MX; 1 through 20 mm for CN and KR; and 0.5 through 2 for Brazil.
  • The width note accepts letters and numbers, is normalized to uppercase, and is displayed only as context.
  • Changing lower or higher rounding moves every scale independently to its configured retail step, so the drift chart should be compared after each change.

Accuracy Notes:

Shoe-size conversion is a guideline. The formulas provide a transparent comparison baseline, while the official ISO conversion standard uses published tables and individual brands use their own lasts, allowances, widths, and available sizes.

  • Measure both feet and use the longer foot; do not infer length from a shoe that already feels too short or too long.
  • Match the retail increments to the specific seller before interpreting a rounded label.
  • Use the brand's model-specific chart and return policy for the final choice, especially for sports footwear, safety shoes, children's growth room, or unusual widths.

Worked Examples:

Starting from EU 42

With a 1.5 cm allowance and nearest default steps, EU 42 back-solves to an estimated 26.5 cm foot and 28.0 cm last. The comparison produces US men's 9, US women's 10, UK 8, BR 40, JP and MX 26.5 cm, and CN and KR 265 mm. EU remains the primary label because it was the starting system; the result still needs the seller's model chart.

References: