About

Incorrect sizing accounts for over 30% of e-commerce returns. Relying on generic "S/M/L" labels across international borders is a gamble due to vanity sizing and lack of standardization. This tool solves the discrepancy problem by cross-referencing regional standards (US, UK, EU, JP) against raw measurements.

Accuracy is paramount when importing garments or purchasing from brands with known fit deviations. This utility includes a brand offset logic to adjust for manufacturers known to run small or large. It processes measurements in both inches and centimeters to determine the optimal fit, reducing the financial and logistical costs associated with returns.

Formulas

The core logic correlates a region-specific label to a standardized measurement index. For exact measurement inputs, the fit determination uses a threshold comparison:

{

Size = S if x ≤ 36Size = M if 36 < x ≤ 40Size = L if x > 40

Where x represents the user's chest or waist measurement in inches.

Reference Data

Region	Men's Suit (Chest)	Women's Dress	Men's Shoe (Length)	Women's Shoe (Length)
US	36	6	9	7
UK	36	10	8.5	5
EU	46	38	42	38
JP (cm)	91.5	9	27	24
US	38	8	9.5	7.5
UK	38	12	9	5.5
EU	48	40	43	38.5
JP (cm)	96.5	11	27.5	24.5
US	40	10	10	8
UK	40	14	9.5	6
EU	50	42	44	39
JP (cm)	101.5	13	28	25
US	42	12	10.5	8.5
UK	42	16	10	6.5
EU	52	44	44.5	39.5
JP (cm)	106.5	15	28.5	25.5

Frequently Asked Questions

Brands use "vanity sizing" to flatter customers, shifting labels down (e.g., labeling a 30-inch waist as 28). Manufacturing tolerances and regional demographics (e.g., average height in Japan vs. Netherlands) also cause significant deviations.

Use a flexible tape measure. For chest, measure under the armpits at the fullest part. For waist, measure at the natural crease just above the navel. Keep the tape snug but not tight. Do not hold your breath.

It improves probability but cannot guarantee fit. The offset applies a statistical adjustment (e.g., −0.5 inches for brands running large) based on aggregated consumer feedback data.

Generally, yes. Japanese shoe sizes (mondopoint) represent the foot length in centimeters. Clothing sizes often follow a numbered system (7, 9, 11) or letter system (S, M, L) that is scaled smaller than US/EU equivalents.