The Problem at the Rack
You buy a size medium in a shirt. It fits. You buy a size medium from a different brand and return it the same week. The number was identical. The garment was not. This is not a coincidence and it is not your body changing between purchases. It is the result of three compounding variables: vanity sizing, block drafting philosophy, and the absence of a shared definition of what a measurement actually is.
Vanity Sizing: A Commercial Decision, Not a Craft One
Vanity sizing is the practice of labeling a garment with a smaller size number than its actual dimensions would historically warrant. A woman's size 8 in 1970 had a roughly 24-inch waist. A garment labeled size 8 today may measure 28 inches or more at the waist, depending on the brand.
The driver is conversion rate. Shoppers who reach for a smaller number and find it fits are more likely to complete the purchase. Brands that sell aspirational positioning tend to size more generously. Brands that sell workwear or technical apparel tend to stay closer to dimensional reality because their customers are measuring themselves and comparing specs.
The result is that a size label communicates almost nothing about the actual dimensions of a garment. It communicates, at best, where a brand has chosen to position that garment relative to its own size run.
Block Drafting: Where the Real Differences Live
A block (also called a sloper) is the foundational pattern from which all garments in a brand's collection are derived. It encodes assumptions about the human body: the ratio of chest to waist, the slope of the shoulder, the length of the torso, the curve of the seat.
Every brand drafts its own block, or licenses one, or inherits one from a factory. Those blocks reflect a specific body model, often built from a single fit model measured at a single point in time. When a brand says this shirt is cut for an athletic fit, what they mean is that their block assumes a narrower waist relative to chest than their standard block does.
Two garments can share an identical chest measurement and diverge completely in how they fit because the block distributes that measurement differently across the body. A 40-inch chest in a brand with a high armhole and a suppressed waist feels nothing like a 40-inch chest in a brand with a dropped armhole and a straight side seam. Both are technically size large. Neither fits the same person the same way.
Key block variables that affect fit
- Shoulder slope: the angle from the neck point to the shoulder tip. Too flat and the sleeve pulls forward. Too steep and it bunches at the armhole.
- Armhole depth and shape: a high armhole allows more arm movement but requires a more precise shoulder fit. A low armhole is more forgiving but restricts overhead reach.
- Back length vs. front length: brands cut these differently based on their assumed posture. A brand that assumes a more upright posture will cut a longer back.
- Seat curve: the amount of curve built into the back rise of trousers. A flatter seat curve fits a straighter body. More curve accommodates a rounder seat without pulling.
- Ease allowance: the amount of extra fabric added beyond the body measurement. A fitted shirt might add 2 inches of ease to the chest. A relaxed shirt might add 6 or more.
What a Measurement Actually Is
This is the part most shoppers and even some buyers miss. A measurement on a garment tag or size chart is almost never a body measurement. It is a garment measurement, taken flat, of the finished piece.
When a brand lists a chest of 40 inches, they typically mean the garment measures 20 inches across the chest when laid flat and doubled. That already includes ease. Your body might measure 38 inches at the chest and fit that garment, or it might measure 40 inches and find the garment too tight because the ease was calculated for a different posture or shoulder width.
Body measurements and garment measurements are two different data sets. Confusing them is the root cause of most fit failures in online shopping. A shopper measures 32 inches at the waist, finds a trouser listed as size 32, and receives a garment that either fits or does not depending on how that brand defines the waist point (natural waist, hip, or somewhere between), how much ease they added, and how their block distributes the fabric across the seat and thigh.
The measurement points that vary most by brand
- Chest: measured at the fullest point, or one inch below the armhole, depending on the brand.
- Waist: measured at the natural waist, or at the waistband seam, which may sit two inches lower.
- Hip: measured at the fullest point of the seat, but the distance from the waistband to that point varies by block.
- Inseam: measured from the crotch seam to the hem, but crotch seam placement varies by rise, and rise is rarely listed.
What This Means for Buyers
Size labels are brand-specific shorthand. They are useful within a single brand's size run and nearly useless across brands. The only reliable unit of comparison is a garment measurement taken at a consistent point, compared against a body measurement taken at the same point with a known ease preference applied.
Independent tailors have always known this. They measure the body, not the label. The growing interest in body scanning tools reflects the same logic: if you know your actual dimensions at consistent landmarks, you can evaluate garment specs directly rather than guessing from a size number.
Alex Folzi is building toward exactly this. The iOS app is currently waitlist-gated and under App Store review. The premise is straightforward: scan once, store your measurements, compare them against garment data. No more size guessing across brands.
The Short Takeaway
A size number is a brand's internal label. A garment measurement is a physical fact. A body measurement is another physical fact. Fit happens when those two sets of facts are compared directly, with ease accounted for. Everything else is guessing.
If you work in apparel sourcing, product development, or procurement and want to think through how measurement standards affect returns and sizing strategy, reach out to the IT Custom Solution team for a brief conversation. No pitch, just a practical exchange.