Shoe Size Converter

Field	Value	Copy
{{ r.label }}	{{ r.value }}

Shoe sizes are shorthand labels for a last length that is matched to a measured foot length with a little extra space for comfort. Conversions help compare regional systems and pick a size that feels right in everyday wear.

Foot length drives the recommendation, then an allowance adds toe room so the last does not press on the toes. A simple way to think about it is measure the foot once, add a small cushion, and read the equivalents across systems.

The tool accepts a direct foot measurement or an existing size from another system so you can translate it cleanly. One practical use is checking if a favorite size in one region corresponds to a sensible choice elsewhere.

Results are rounded to the nearest step used by each system so what you see lines up with real shelf sizes. If your value sits close to a boundary, consider the toe room and the intended socks to avoid a feel that is too tight.

Entering a width code is optional and shown for reference only. Conversions are unisex; the gender choice changes labeling, not the math.

Technical Details:

The quantities observed are foot length in centimetres or inches and a fit allowance for toe room. The allowance is added to foot length to form the last length, which is the basis for size numbers used in different systems.

Computation proceeds by converting units once, then applying linear formulas that map last length to size indices. Where systems label the shoe by foot length instead of last length, the index equals the measured foot length in the stated unit.

Results are expressed in the following systems with one expansion each: United States Men and Women (US Men, US Women), United Kingdom (UK), European (EU), Brazil (BR), Japan Mondopoint in centimetres (JP), Mexico in centimetres (MX), China in millimetres (CN), and Korea in millimetres (KR). A rounding step is applied per system using one of three modes: nearest, floor, or ceil.

Interpretation focuses on toe room and step edges. Very small toe room suggests a snug feel, a moderate mid‑range is typical for daily wear, and larger values read as roomy. Because brand lasts differ, treat any single number as a starting point.

\begin{matrix} L f_{cm} & = & foot length (cm) \\ A & = & allowance (cm) \\ L l_{cm} & = & L f_{cm} + A \\ L l_{in} & = & \frac{L}{l_{cm}} \\ s_{UK} & = & 3 \cdot L l_{in} - 25 \\ s_{USM} & = & 3 \cdot L l_{in} - 24 \\ s_{USW} & = & 3 \cdot L l_{in} - 23 \\ s_{EU} & = & 1.5 \cdot L l_{cm} \\ s_{BR,raw} & = & s_{EU} - 2 + Δ {BR}_{offset} \\ s_{JP} & = & L f_{cm} \\ s_{MX} & = & L f_{cm} \\ s_{CN} & = & 10 \cdot L f_{cm} (mm) \\ s_{KR} & = & 10 \cdot L f_{cm} (mm) \end{matrix}

Symbols and units
Symbol	Meaning	Unit/Datatype	Source
$L f_{cm}$	Foot length	cm or in	Input
$A$	Fit allowance (toe room)	cm	Input
$L l_{cm}$	Last length	cm	Derived
$L l_{in}$	Last length	in	Derived
$s_{⋯}$	Size index per system	number	Derived
$Δ {BR}_{offset}$	Adjusts BR relative to EU	integer	Input

Worked example

Foot length 26.00 cm and allowance 1.5 cm give a last length of 27.50 cm, which is 10.8268 in.

\begin{matrix} s_{UK} & = & 3 \cdot 10.8268 - 25 = 7.4803 \to 7.5 \\ s_{USM} & = & 8.4803 \to 8.5 \\ s_{USW} & = & 9.4803 \to 9.5 \\ s_{EU} & = & 1.5 \cdot 27.50 = 41.25 \to 41.5 \\ s_{BR} & = & 41.25 - 2 = 39.25 \to 39 \\ s_{JP} & = & 26.0 cm \\ s_{CN} & = & 260 mm \end{matrix}

Rounded with default steps, the result is US Men 8.5, US Women 9.5, UK 7.5, EU 41.5, BR 39, JP/MX 26.0, CN/KR 260 mm; toe room is 15 mm.

Approximate toe-room zones
Zone	Lower (mm)	Upper (mm)	Implication
Snug	0	5	Very close cut; watch nail contact.
Standard	5	15	Typical day‑to‑day comfort zone.
Roomy	15	25	Extra space; useful for thick socks.

Validation & bounds extracted from code

Inputs and constraints
Field	Type	Min	Max	Step/Pattern	Notes
Mode	enum	—	—	foot_cm, foot_in, us_m, us_w, uk, eu, jp_cm, mx_cm, cn_mm, kr_mm, br	Controls how value is interpreted.
Value	number	0	—	step 0.01	Primary input in selected unit.
Gender	enum	—	—	men, women	Affects label only.
Width	string	—	—	^[A‑Z0‑9]+$	Uppercase letters and digits; spaces removed.
Allowance	number	0	—	step 0.1	Typical 1.0–1.8 cm.
Rounding	enum	—	—	nearest, floor, ceil	Nearest uses standard half‑up on the step multiple.
US/UK step	number	0.1	—	default 0.5	Half sizes typical.
EU step	number	0.1	—	default 0.5	Half sizes may be uncommon.
JP/MX step	number	0.1	—	default 0.5	Mondopoint uses cm steps.
CN step	number	1	—	default 5	Millimetre increments.
KR step	number	1	—	default 5	Millimetre increments.
BR step	number	0.5	—	default 1	Whole sizes common.
BR offset	number	—	—	step 1	Typical mapping near EU−2; adjustable.

I/O formats & rounding

Input and output formats
Input	Accepted Families	Output	Encoding/Precision	Rounding
Foot length	cm, in	Sizes and lengths	two decimals for lengths	to step per system
Regional size	US Men/Women, UK, EU, BR, JP/MX, CN/KR	Foot and last lengths	cm and mm as applicable	to step per system

Networking & storage behavior

All calculations run locally in the browser on your device.
A lightweight charting layer is loaded for visuals; no external services are queried for results.
No data is transmitted or stored server‑side.

Assumptions & limitations

Brand lasts vary; a mathematically valid size may fit differently across models.
EU half sizes may be scarce in retail Heads‑up.
BR mapping uses an adjustable offset and is approximate by ±1 size Heads‑up.
Width codes are displayed as text and do not change results.
Adult foot length outside 18–31 cm triggers a caution as atypical.
Rounding mode changes the recommended size at boundaries.
Sock thickness and swelling are not modeled.
Measurement error of a few millimetres can change the suggestion near cut‑points.

Edge cases & error sources

Using inches while the mode expects centimetres.
Allowance set below 0.5 cm or above 2.0 cm leading to atypical fits.
Values exactly on a half step rounding up or down unexpectedly.
Custom steps set unrealistically small, producing noisy results.
BR offset sign reversed, shifting recommendations by two sizes.
Copying width codes with spaces or punctuation; non‑alphanumerics are ignored.
Entering zero or negative lengths; such inputs produce no results.
Millimetre systems compared directly to centimetre systems without unit awareness.
Floating‑point display differences at two decimals vs internal precision.
Comparing sizes across men and women labels without noting the offset in formulas.

Step‑by‑Step Guide

Foot‑based sizing with toe‑room control and rounded shelf sizes.

Choose the input type and enter the Value.
Select a fit allowance or use a preset for snug, standard, or roomy.
Pick a rounding mode to match how sizes are offered.
Optionally enter a width code for reference.
Review the primary recommendation and the equivalents across systems.

Example: 26.0 cm with 1.5 cm allowance suggests US Men 8.5 and EU 41.5 with about 15 mm of toe room.

If you are between sizes, compare toe room and intended socks.
Switch rounding to floor for a tighter cut or ceil for extra space.

FAQ

Is my data stored?

No. Calculations run on your device and no results are sent to a server.

Copy and download actions operate locally.

How accurate are conversions?

Formulas are deterministic, but brand lasts differ. Treat results as a strong starting point and check toe room against your use.

EU halves and BR offsets vary by maker.

What units and formats are accepted?

Centimetres, inches, and regional size numbers. China and Korea use millimetres; Japan and Mexico use centimetres.

Width codes accept letters and digits only.

Can I use it without a connection?

Yes. Once loaded, computations work without a network.

Charts are rendered locally.

How do I convert Mondopoint to US men?

Use JP centimetres as input. The US men size is computed from last length in inches with the formula 3×L_in−24, then rounded to the chosen step.

Change rounding to match shelf sizes.

What does a “borderline” result mean?

You are near a step edge. Check toe room and consider floor for snug or ceil for extra space.

Sock thickness can shift comfort by a step.

Does gender change the math?

No. It selects the primary label. The equations remain the same.

Display only.

Troubleshooting

No output shown: ensure the value is above zero.
Results feel tight: increase allowance or switch rounding to ceil.
Results feel loose: reduce allowance or switch rounding to floor.
EU halves look off: many brands skip them; set EU step to 1.0.
BR looks misaligned: set BR offset to −2 to follow the common mapping.
Millimetres vs centimetres: confirm the mode before entering numbers.

Nothing changes after edits? Clear any invalid characters in the width field and re‑enter the numeric value.

Glossary

Foot length: Heel to longest toe measurement on a flat surface.
Last length: Internal length the size is built around.
Allowance: Extra space added for comfort and motion.
Mondopoint (JP): Sizing by foot length in centimetres.
Step size: Increment between adjacent labels in a system.
BR offset: Adjustment aligning BR and EU numbering.