No universal conversion
A French size has no fixed UK or US equivalent: each brand sets its own correspondence. Be wary of generic tables.
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Fashion · The guideCreate a size chart.
The right measurements, the right ease, one chart per family. How to build a reliable size chart for your online store.
- 5 steps
- Standards cited
- 7 common mistakes
In short
How do you create a reliable size chart?
In short: a reliable size chart gives each size a range of body measurements in centimetres: chest girth for a top, waist girth for trousers. It is specific to each product family, takes the ease of the cut into account, explains how to measure and is checked against real garments.
Size designation standards are based on body measurements, not garment measurements (ISO 8559-2). Garment measurements are left to the brand, which adds the ease it wants.
Method
A size chart in five steps.
- 1
Choose the deciding measurement
For each family, the main body measurement: chest, waist, neck. Add one or two secondary measurements, such as height or inside leg.
- 2
Give ranges
For each size, a range in centimetres, with no gap and no overlap with the next size.
- 3
Start from your garments
Measure the garments from your production, then work out the ease of the cut. Do not copy another brand's chart.
- 4
Explain how to measure
Where to place the tape measure, over which clothes, standing or sitting. A diagram beats a paragraph.
- 5
Check and correct
Compare the chart with size-related exchanges and returns, product by product, and correct it.
Which measurements
The deciding body measurement, family by family.
The primary and secondary dimensions of EN 13402-2, carried over into ISO 8559-2.
| Family | Men: main measurement | Women: main measurement | Secondary measurements |
|---|---|---|---|
| Jackets, coats | Chest girth | Bust girth | Height, then waist (men) or hip girth (women). |
| Trousers, shorts | Waist girth | Waist girth | Height, inside leg, and hip girth for women. |
| Shirts, blouses | Neck girth | Bust girth | Height, and arm length for men. |
| Dresses | None | Bust girth | Height, hip girth, waist girth. |
| Knitwear (jumpers, T-shirts) | Chest girth | Bust girth | Depending on the model. |
| Skirts | None | Waist girth | Depending on the model. |
Measurements are given in centimetres. ISO 8559-1 describes how to take each body measurement: a good basis for writing your own measuring instructions.
Body, garment, ease
Body or garment measurements: do not mix them up.
| Type of measurement | What it describes | In the chart |
|---|---|---|
| Body measurement | The person who will wear the garment: chest, waist, hip girth. | The basis for choosing a size. Shoppers compare it with their own measurements. |
| Garment measurement | The garment laid flat: width, length, sleeve length. | An extra, mainly for length. Label it clearly. |
| Ease | The difference between the two: the room the garment allows beyond the body. | Why a slim cut and a loose cut do not share the same chart. |
Key point: wearing ease lets you move and sit; design ease creates the intended cut. The same body can therefore take an M in a loose cut and an L in a slim cut from the same brand. One chart per family, and one per cut when the ease changes.
International
Selling abroad without a rough conversion table.
Centimetres first
Show body measurements in centimetres, and in inches for markets that use them: 1 inch = 2.54 cm.
A language-neutral pictogram
EN 13402-1 and ISO 8559-1 provide a pictogram showing the body measurements a garment is meant to fit, readable in any language.
Common mistakes
Seven mistakes that make a size chart useless.
- One chart for the whole catalogue. Jeans and a jumper are not chosen with the same measurement.
- Garment measurements presented as body measurements. The shopper compares their chest girth with a flat width and gets it wrong.
- A chart copied from another brand or from the supplier, without checking it on your garments.
- Ranges that overlap or leave gaps between two sizes.
- No measuring instructions. Everyone measures their own way and the chart loses its value.
- A generic international conversion table instead of your own measurements.
- A chart never updated when the cut, fabric or manufacturer changes.
WeeFizz Fashion
From size chart to recommended size.
An accurate chart is still a table of centimetres. Shoppers rarely know their measurements. The widget does the calculation for them.
The shopper answers
Height, weight, age, gender and body shape chosen from images, on the product page. No photo needed, no tape measure.
14 measurements are estimated
The WeeFizz engine derives 14 girth and length measurements, then compares them with your chart, taking ease and fit into account.
One size per product
Your size chart is set up product by product. Shoppers see their size before adding to basket.
WeeFizz does not keep a universal size-chart database: your own chart is the one used. A recommendation is the best estimate possible from that chart; WeeFizz does not claim zero errors. Your dashboard tracks widget usage, recommended sizes and conversion, product by product. Find out more: how size recommendation works and WeeFizz Fashion, size recommendation for e-commerce.
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Frequently asked questions
Creating a size chart: your questions.
How do you create a size chart for an online store?
For each product family, choose the body measurement that decides the size (chest girth for a top, waist girth for trousers), give each size a range of measurements in centimetres, explain how to measure, then check the chart against real garments from your production.
Should a size chart give body or garment measurements?
Body measurements are used to choose the size: they are the basis of the size designation standards (ISO 8559-2, EN 13402). Flat garment measurements are a useful extra, for example for length. If you give both, say clearly which is which.
What is ease in a garment?
It is the room a garment allows beyond the body's measurements. Wearing ease lets you move and sit; design ease creates the intended cut, slim or loose. That is why the same body does not take the same size in two different cuts.
Is one size chart enough for the whole catalogue?
Rarely. Jeans, a shirt and a jumper are not chosen with the same measurement, and two cuts in the same family do not have the same ease. Plan at least one chart per product family, and one per cut when the ease changes.
How do you handle international sizes?
There is no universal conversion table between French, UK or US sizes: each brand has its own. The most reliable approach is to show body measurements in centimetres, and in inches for shoppers who use them (1 inch = 2.54 cm).
Does a size recommendation widget replace the size chart?
No, it relies on it. With WeeFizz, the shopper answers a few questions, with no photo needed, and their size is calculated in your product's size chart. An accurate chart gives an accurate recommendation.
Sources: ISO 8559-1:2017, anthropometric definitions for body measurement (EVS listing); ISO 8559-2, primary and secondary dimension indicators, replaced by the 2025 edition (EVS listing); Wikipedia, EN 13402, table of primary and secondary dimensions; Wikipedia, ease (wearing ease and design ease). Checked on 11 October 2026. Page published by WeeFizz.
WeeFizz Fashion
Your size chart, turned into a size.
Shoppers answer a few questions, with no photo needed, and see their size calculated in your chart. 14-day free trial.