A clothing size chart lists the finished garment measurements for every size, and garment grading rules define how much each point of measure grows or shrinks from one size to the next. You start from one approved base size, choose the points of measure, set an increment for each and add a tolerance. Then you check a graded size set on bodies before bulk production.
Key points
- Everything is graded from one approved base size, so get the base fit right first.
- Points of measure must say exactly where and how each measurement is taken.
- Grade rules are the increments between sizes, and they differ per point of measure.
- Tolerances set how far a finished garment may vary and still pass inspection.
- Always check a graded size set, not only the base sample, before bulk production.
What a size chart and grading are
A size chart is the table of finished garment measurements for each size you sell. Grading is the technical work behind it: taking the pattern of one size and enlarging or reducing it to make every other size, while keeping the shape, proportions and fit of the original.
The two belong together. The size chart says what each size should measure; the grade rules say how the pattern changes to get there. If either one is unclear, the small size and the large size of the same style can end up fitting like two different garments.
Start with a base size and points of measure
Every graded range starts from one base size, also called the sample size. It is usually a middle size, such as 38 or M for women's wear, because grading up and down from the middle keeps the errors small at both ends. All fitting work happens on this size first.
Next come the points of measure: chest, waist, hip, body length, shoulder, sleeve length, armhole, neck width, hem width and any other measurement that matters for the style. Each one needs a short description of where and how it is taken, for example chest measured flat, one centimetre below the armhole, from side seam to side seam. Most fit disputes start with a point of measure that two people measured in different ways.
Grade rules: the increment between sizes
A grade rule is the amount a point of measure changes between one size and the next. Circumferences such as chest, waist and hip change the most; lengths, shoulders and necklines change much less. Garment grading rules are written per point of measure, never as one number for the whole garment.
Here is a simple example for a women's woven dress with a base size of 38. The numbers are an illustration, not a standard; your own increments depend on your customers and your fit.
- Chest circumference: 92 cm at size 38, plus or minus 4 cm per size
- Waist circumference: 74 cm at size 38, plus or minus 4 cm per size
- Hip circumference: 98 cm at size 38, plus or minus 4 cm per size
- Shoulder width: 38 cm at size 38, plus or minus 1 cm per size
- Sleeve length: 60 cm at size 38, plus or minus 0.5 cm per size
- Centre back length: 105 cm at size 38, plus or minus 1 cm per size
Regular and irregular grading
Regular grading uses the same increment between every pair of sizes. It is simple to calculate and easy to check, and it works well for a short range of three to five sizes.
Irregular grading changes the increment along the range. Bodies do not grow evenly: larger sizes often need bigger steps in the waist and hip, and the smallest sizes need smaller steps so that shoulders and necklines do not become too narrow. A brand with an extended range, or with plus sizes, usually needs irregular grading or a second base size for the larger group. Lengths are often kept fixed across a range, or graded in two groups, rather than growing with every size.
Tolerances
No sewn garment comes out exactly at the measurement on paper. Fabric shrinks, stretches and moves under the machine. A tolerance is the allowed difference between the size chart and the finished garment, written for each point of measure.
Larger circumferences usually get a wider tolerance, often around 1 cm either way, while small points such as neck width or cuff opening get a tighter one, often around 0.5 cm. Stretch fabrics may need wider tolerances than stable wovens. Keep each tolerance smaller than half of the grade step, otherwise a garment at the limit of one size can measure like the neighbouring size.
Women's, men's and kidswear conventions
Women's wear is usually labelled with number sizes or with letter sizes. In general terms, a European 38 is often labelled UK 10 and US 6, but brands vary and these conversions are a habit, not a rule. Men's tops are mostly sold in letter sizes or by chest or collar measurement, and men's trousers by waist and inside leg. Kidswear is commonly sized by body height in centimetres in Europe and by age in the UK and US, with bigger steps between sizes because children grow fast.
The European standard EN 13402 describes size labelling based on body measurements. Whether you must follow it, and what your size and care labels have to show, depends on the market and on the retailers you sell to, so confirm the requirements with your buyers or the relevant authority before you print labels.
How to build a size chart for a new brand
A new brand does not need to invent a sizing system from nothing. These steps give you a size chart you can defend and repeat across every style.
- Define your customer and pick the size range you will actually sell
- Choose a base size in the middle of that range
- Measure a few garments you know fit your customer well, and use them as a reference
- List the points of measure for the style, with a note on how each is taken
- Set the grade rule and tolerance for each point of measure
- Write body measurements for customers and garment measurements for the factory, and keep them apart
- Reuse the same grading across styles so your sizes feel consistent to the customer
How to check graded samples
Grading is checked on a size set: the same style sewn in several sizes, usually the smallest, the base and the largest. Measure each sample against the size chart and try them on real people who match those sizes, not only on the base fit model.
Look for the problems that only appear at the ends of the range: necklines that gape in the large size, armholes that cut in at the small size, pockets and prints that land in the wrong place, and hems that sit at a different point on the leg. In our Istanbul workshop, our pattern makers grade patterns in house and we sew a size set before bulk, so corrections go back into the pattern and not into the finished order.
- Every point of measure is within tolerance in every size
- Proportions look right in the smallest and largest sizes
- Prints, pockets and logos are placed correctly in every size
- Approved corrections are written back into the pattern and the tech pack