You buy a size M shirt that fits perfectly, order the same letter size from another brand, and it arrives fitting like a small tent — or a child’s tee. This isn’t your imagination. US women’s clothing sizes have drifted upward for decades, a practice called vanity sizing, and the gap between two brands’ size M can now exceed 10 cm at the chest.
If you’re tracking body measurements over time (waist, chest, or hip circumference changes across the years), our body-measurement notes pair naturally with a date-of-birth tool for logging how measurements shift with age.
How Much Do Sizes Actually Differ?
| Garment | Brand A “M” (chest) | Brand B “M” (chest) | Difference |
|---|---|---|---|
| Women’s tee | 94 cm | 104 cm | +10 cm |
| Men’s button-up | 97 cm | 104 cm | +7 cm |
| Jeans (waist) | 76 cm / W30 | 82 cm / W30 | +6 cm |
A 2016 study of more than 5,000 garments found men’s waist sizes had inflated by about 8 cm since the 1950s, while women’s had grown even more. The label number stayed the same; the actual garment got larger.
The Reliable Fix: Measure, Don’t Guess
Every brand publishes a size chart, and the only number that matters is your body measurement against that specific chart. The process takes two minutes:
- Chest: measure around the fullest part, tape horizontal, arms down.
- Waist: measure at the narrowest point, usually just above the navel.
- Hip: measure around the fullest point of the seat.
- Inseam: measure from crotch seam to hem on a pair of trousers that already fit.
Then match those numbers to the brand’s chart, ignoring the letter on your old favourite shirt entirely.
Why Vanity Sizing Exists
Retailers discovered that customers buy more when they can wear a “smaller” size. Shifting a size M up by 4 cm lets a person who was a size L five years ago now fit into a medium — and feel better about it. The effect compounds: what was a size 12 in 1970 is close to a size 6 in many modern lines.
Brand-to-Brand Practical Rules
- Fast fashion tends to run smaller and less consistent within its own range.
- Athletic brands often run a half-size to a full size smaller than dress brands.
- Luxury and European brands usually run truer to measurement but cut slimmer.
- Made-to-measure or size-chart-first brands are the most predictable — the number means what it says.
FAQ
Should I keep a “reference shirt” to compare against? Yes — the flat-lay measurement of a garment that fits is often more useful than your body measurement, because it also accounts for the cut and fabric stretch.
Do men’s sizes drift too? Yes, though more slowly. Men’s waist and shoe sizes have both inflated measurably over the past 60 years.
What about children’s clothing? Kids’ sizes are anchored to height and weight bands and are more consistent than adult sizes, but brands still vary by up to one size.
The letter on the tag is a marketing convention, not a measurement. Buy by the tape, not the label.
