The short answer
Build the size chart from the body measurements of the customers you intend to fit, and keep it separate from the garment specification. ISO 8559-2 designates sizes by body dimensions—bust or chest girth for tops, waist or hip girth for adult leggings, and bust plus underbust girth for bras—while garment measurements, ease and grading remain design decisions. Publish each size as a body-measurement range, state the unit, test the ends of each range in real samples and update the chart whenever the pattern or fabric changes.
Letters and numbers are labels; the body ranges behind them are the chart.
Garment measurements, ease and tolerances belong in the specification, not the published chart.
No conversion table makes one brand’s sizes match another brand’s.
What is a size chart for, and what does sizing mean?
Sizing is the system that links a size label to the bodies a garment is designed to fit. ISO 8559-2:2025, the international standard for clothing size designation, describes its aim as telling consumers, simply and directly, the body dimensions of the person a garment is intended to fit. Its system is based on body measurements, not garment measurements; how much larger or smaller the garment is than the body stays a decision for the designer and manufacturer. In textile processing, “sizing” can also mean a treatment applied to yarn; this guide uses the clothing meaning.
That separation is the foundation of a usable chart. The published size chart describes bodies: the customer measures themselves and finds a range. The garment specification—points of measure, graded measurements and tolerances—describes the product and stays with the pattern and production files. When a brand publishes flat garment widths as if they were body measurements, customers compare two different quantities and can pick the wrong size.
Which body measurements belong on an activewear size chart?
ISO 8559-2 gives each garment type a primary dimension—the body measurement that designates the size—plus optional secondary dimensions. It lists men’s, women’s, boys’ and girls’ clothing separately and expresses primary dimensions in centimeters, measured as ISO 8559-1 defines them. Use that structure as the backbone of your chart, and add a secondary measurement only when it changes the customer’s choice, such as inside leg length for a legging sold in several lengths.
| Product | Body measurements to publish | Garment measurements kept in the specification (examples) |
|---|---|---|
| T-shirts and tops | Bust girth for women’s styles, chest girth for men’s; height as an option | Chest width, body length, sleeve length, neck opening |
| Leggings, pants and shorts | Waist and hip girth, with height or inside leg length for length | Waist, hip, front and back rise, inseam, leg opening |
| Sports bras | Underbust and bust girth; cup size is the difference between them | Underband length, cup or panel depth, strap length |
| Children’s styles | Body height first, with girths as secondary guidance | The same points of measure, graded by height range |
| Tights (pantyhose) | Height, with weight in kilograms as a secondary guide | Waist, leg length and relaxed width |
How do body ranges become garment measurements and grades?
A body chart does not tell a pattern maker how big to cut. ASTM’s misses body-measurement tables (D5585) make the same point: they list body measurements that can serve as a design baseline once fabric type, ease for movement, styling and fit are considered. Close-fitting activewear is often cut smaller than the body, so the difference depends on the fabric’s stretch and recovery and on how much compression the style intends.
Fit the base size on a wearer whose measurements sit inside that size’s published range; the fit-model guide covers that selection. Then write grade rules point by point and give each point of measure a tolerance the material and construction can hold. Where the range changes body shape, a separate block may be needed, as the extended-size grading guide explains. Sample the sizes that expose the grade before publishing; the size-set guide sets out what that review should prove.
Letters, numbers and regions: which size chart should you use?
There is no universal chart to copy. ISO 8559-2 itself observes that because companies use different sizing systems, different size labels can fit people with identical or very similar measurements. A “10” or an “M” means nothing until it is tied to your body ranges. ASTM D5585 publishes body tables for an adult female misses range labeled 00 to 20, yet another brand using the same numbers may fit different bodies.
Regional references differ as well. Standards Australia lists its women’s size coding scheme, AS 1344-1997, as withdrawn, with no newer edition shown, so a brand selling there should publish its own body ranges. China’s national standard for women’s garment sizing, GB/T 1335.2-2008, is listed as current and follows its own designation system. When a supplier’s sizes seem small, ask which reference body its default block was built for; the letter on the label cannot tell you.
For multi-market sales, publish body measurements instead of a label-conversion table. ISO 8559-2 treats centimeters as its official unit and requires inch values, where used, to be reported separately rather than mixed; ASTM D5585 likewise treats SI and inch-pound values as separate systems that may not be exact equivalents. Choose a master unit, convert once with consistent rounding and show both columns. A UK, Australian or Canadian shopper then compares the same body ranges; only the display unit changes.
What does one size mean for leggings and tights?
A one-size legging or tight is a single graded size meant to fit a declared range of bodies through stretch. It still needs a size chart, just with one row. Under ISO 8559-2, a range is written as the minimum and maximum body dimensions the garment was designed for, and for adult pantyhose the standard uses height as the primary dimension with weight as a secondary one.
For a one-size legging, publish that range—for example waist and hip girth plus height—and fit-test samples on wearers at both ends and in the middle. Check coverage, waistband position and opacity at the largest end, and length and excess fabric at the smallest. If either end fails, narrow the stated range or add a second size rather than stretching the promise. Weight alone is a weak guide for fitted activewear because it does not show where the body carries its measurements.
How should you publish and maintain the size chart?
Publish the chart where the customer decides; ISO 8559-2 expects size information at the point of sale, including websites. Show how to take each measurement with a simple diagram, state the unit, and add a short fit note per style—such as whether to size up between sizes—only where wear reviews support it. If you also show garment measurements, put them in a separate, clearly labeled table, as the standard advises, so they are not mistaken for body measurements.
Bra charts are two-dimensional: underbust girth sets the band, and the difference between bust and underbust girth—ISO 8559-2’s definition of cup size—sets the cup. A sports bra sold in letter sizes still needs both ranges for each size. The sports bra manufacturing guide covers the support system a chart cannot describe, and the leggings manufacturing guide covers the coverage and waistband checks behind each legging size.
Treat the chart as a controlled document. Give it a revision date, tie it to the pattern and fabric it was validated with, and re-check it when either changes. Log returns and fit comments by size, so a recurring pattern—customers between two sizes consistently choosing the smaller, for example—leads to a reviewed change through pattern and fit engineering rather than a quiet edit on one product page.
Decision map from this guide
| Decision area | What this guide establishes |
|---|---|
| Choosing what the chart shows | Use each garment type’s primary body dimension, then add only the secondary ones customers need. |
| Selling in several markets | Publish body ranges in centimeters and inches instead of a label-conversion table. |
| A supplier’s stock sizes feel small | Ask for the body measurements behind each label; grade your own pattern. |
| One-size leggings or tights | State the minimum and maximum body range, then fit-test both ends. |
| Pattern or fabric changes | Re-check the chart against new samples before it goes live again. |
Sources and scope
ISO 8559-2:2025, ASTM D5585-21 and the Standards Australia and SAMR national-standard records support only the specific sizing-standard facts cited. The chart structure, grading steps and publishing checklist are MOTIONFORM editorial guidance, not a size standard, customer chart or fit result. Sources reviewed 27 September 2026.
- ISO 8559-2:2025: size designation of clothes—primary and secondary dimension indicators (reviewed 27 September 2026)
- ASTM D5585-21: body measurements for the adult female misses figure type, size range 00–20 (reviewed 27 September 2026)
- Standards Australia: AS 1344-1997 size coding scheme for women’s clothing, listed as withdrawn (reviewed 27 September 2026)
- SAMR national standards platform: GB/T 1335.2-2008, standard sizing systems for garments—women (reviewed 27 September 2026)
Buyer questions
What is the purpose of sizing?
Sizing tells a customer which garment is intended to fit their body. A useful system ties every label to published body-measurement ranges, so customers compare their own measurements instead of guessing from a letter or number. For the brand, the same system connects the chart to base-size fitting, grading and the garment specification used in production.
Should a size chart be in inches or centimeters?
Show both if your customers use both, but keep one master unit. International size designation uses centimeters, and standards that allow inches treat the two systems separately because converted values are not always exact equivalents. Convert once, round consistently and check that neighboring sizes neither overlap nor leave gaps after rounding.
Can I convert US sizes to UK or Australian sizes with one table?
Not reliably. Different brands can attach different labels to garments for the same body, so a generic conversion table only moves the confusion. Publish body-measurement ranges for your own sizes and let customers in every market compare against those. If a retailer requires a local label, map it from your measurements and state that basis.
Why do sizes from Chinese suppliers often seem small?
The letter is not the problem; the missing measurements are. China has its own national garment-sizing standards, and a supplier’s default block may be built for a different reference body than your customers. Ask for the body ranges behind each size, fit your base size on your own target wearer and grade from there instead of relabeling stock sizes.
What does size 10 mean in leggings?
Only what the brand’s chart says it means. Numeric sizes appear in several systems—ASTM’s misses tables run from 00 to 20, for example—and the same number can describe different bodies in different brands’ charts. Compare the waist and hip ranges, plus height or inside leg length where given, with your own measurements instead of assuming one brand’s 10 matches another’s.
How do I know what size leggings to choose?
Measure your waist and hips the way the brand’s diagram shows, then find the size whose ranges include both. Add height or inside leg length if the style comes in several lengths. If your measurements fall in different sizes, follow that style’s fit note, because compressive and relaxed styles may call for different choices.
Should a size chart include weight or age?
Only as secondary guidance. ISO 8559-2 designates infant sizes by body height and lists weight only as a secondary measure for items such as pantyhose. Age and weight do not show where a body carries its measurements, so publish height and girth ranges first and treat any age label on youth or baby sizes as approximate. Children’s products may also carry separate safety requirements.
Do men’s and women’s size charts need different measurements?
Yes. ISO 8559-2 lists men’s, women’s, boys’ and girls’ clothing separately; a men’s T-shirt is designated by chest girth and a women’s by bust girth. A unisex style can share one chart, but it then needs a clear fit note and wear reviews on both groups of wearers, because the same garment sits differently on different bodies.
