The Number on the Chart Is Not the Number on the Garment
You measure your chest: 96 cm. The size chart says Large starts at 96 cm. You order a Large. The shirt arrives and the chest seam sits two centimeters past your shoulder point. The fit is wrong, but the size was technically correct.
This is the central confusion in apparel sizing. A size chart entry and a finished garment measurement are two different numbers serving two different purposes. Conflating them is the most common reason a correctly sized purchase still fits badly.
Body Measurements: What You Are
Body measurements describe the person. Chest circumference, waist circumference, hip circumference, inseam, back length, shoulder width. These are taken against the body, usually with a tape held snug but not tight.
Size charts built on body measurements tell you which size range a garment is intended for. They do not tell you how the garment itself is cut. A brand's size chart saying "chest 96-100 cm" for a Medium means the garment is designed for a person whose chest falls in that range. It says nothing about how many centimeters of fabric actually span the front and back panels.
Garment Measurements: What the Fabric Does
Garment measurements, sometimes called finished measurements or spec measurements, describe the physical object laid flat. Chest width on a finished shirt is measured across the front panel, one centimeter below the armhole, then doubled. That number is the actual interior space available to your body.
The difference between your body measurement and the finished garment measurement is called ease. Ease is intentional. A woven dress shirt might add 10-14 cm of ease to the chest so you can button it, breathe, and move your arms. A slim-cut jersey T-shirt might add only 4-6 cm. A structured blazer adds ease at the chest but often very little at the sleeve head, which is why raising your arm in a tailored jacket feels different from raising it in a sweatshirt.
Ease is not a flaw. It is a design decision. But it varies by brand, by garment category, and by silhouette. A size chart that lists only body measurements tells you nothing about how a specific brand has distributed ease across a specific style.
Why Patternmakers Think Differently
A patternmaker starts from a base block, which is a foundation pattern built to a set of body measurements with a defined ease allowance already drafted in. When they grade a block from a size 10 to a size 12, they are not simply adding two centimeters everywhere. They are redistributing ease across specific seam lines: side seams, back width, sleeve cap height, dart intake. The relationship between body measurement and garment measurement is engineered at each point.
This is why two brands can both list "waist 76 cm" for a size 10 trouser and produce trousers that feel completely different. One brand may have drafted the block with 2 cm of ease at the waist and 6 cm at the seat. Another may have 4 cm at the waist and 4 cm at the seat. Same body measurement target. Different garment geometry.
Reading a size chart like a patternmaker means asking: what ease assumption is baked into this chart, and does it match the silhouette I am looking at?
How to Use This in Practice
For shoppers
- Find the finished garment measurements, not just the size chart. Many brands publish them in a second tab or below the main size grid. If they are not listed, measure a garment you already own that fits well and compare.
- Measure the garment flat. Chest: across the front, one centimeter below the armhole, doubled. Waist: across the narrowest point, doubled. Hips: across the widest point below the waist, doubled. Sleeve: from center back neck to cuff, or from shoulder seam to cuff depending on the brand's convention. Note which convention the brand uses before comparing.
- Subtract your body measurement from the finished garment measurement. That gap is the ease you will be wearing. Decide whether that amount suits the silhouette and your preference.
For tailors
- When a client brings a garment for alteration, measure the garment first, then measure the client. The difference tells you what the original designer intended and how far you can alter before you are fighting the cut rather than refining it.
- A trouser with 2 cm of ease at the thigh cannot be let out 4 cm without adding fabric. Knowing the finished measurement before you quote the job prevents the conversation where the alteration is technically impossible at the price discussed.
For brands and buyers
- Publish both. A size chart with body measurements tells the customer what size to choose. A finished garment measurement chart tells them what the product actually is. Brands that publish both see fewer returns driven by fit confusion.
- When reviewing a tech pack, confirm that the ease allowance is stated explicitly, not implied. "Chest 100 cm" on a spec sheet means nothing without knowing whether that is the body measurement target or the finished garment measurement. The two numbers belong in separate columns.
The Practical Test
Take any garment in your wardrobe that fits well. Measure it flat: chest, waist, hips, shoulder width, sleeve length. Write those numbers down. Now measure your body at the same points. The difference at each location is the ease profile you actually prefer for that garment category and silhouette. Use that profile as a filter when reading size charts for future purchases.
This is not a complicated process. It takes ten minutes and a tape measure. It converts a size chart from a rough guide into a precise decision tool.
Takeaway
A size chart entry is a targeting tool: it points you toward a size range. A finished garment measurement is a fit tool: it tells you what you will actually wear. Both numbers matter. Neither one alone is sufficient. Learn to read them together, and the gap between "correct size" and "good fit" closes considerably.
Alex Folzi is building toward a simpler version of this process: scan once, store your measurements, compare against garment specs directly. The iOS app is currently waitlist-gated and under App Store review. Join the waitlist if you want early access when it opens.
If your team works with apparel data, sizing systems, or fit technology at scale, the IT Custom Solution contact page is a good starting point for a brief conversation about how managed services and data infrastructure can support that work.