What guessing actually involves
Reading a label, comparing it to your vague sense of your size, and estimating which of two options is less wrong. Every step is uncertain.
And the label itself is unreliable. Across over 1,000 garments in 50 UK brands, only 64% matched their own published chart within 1 cm, with 4.2 cm of average within-brand variance.
What measuring involves
Comparing a number you know to a number the brand published. One uncertain step instead of three.
The measured number has error too, around 2.5 to 6.1 cm depending on the measurement. But that error is known and consistent.
A bounded 6 cm error you can plan around beats an unbounded guess you cannot.
The realistic gain
Measurements remove the uncertainty about your body. They leave the uncertainty about the garment untouched.
For a brand whose chart is accurate, this is decisive. For a brand whose chart is off by 4 cm, you are still guessing about a different number.
Where guessing hurts most
- When you sit between sizes, since guessing has no basis.
- At larger sizes, where chart accuracy falls to 54% at UK 20-22.
- For fitted garments, where a few centimetres decides the outcome.
- Across new brands, where you have no calibrated experience.
Where guessing is fine
- Reordering a garment from a brand you know well.
- Loose, forgiving fabrics.
- Items you would return cheaply anyway.
Add the missing half
Measurements cover your body. Fit reviews cover the garment. Using both removes considerably more uncertainty than either alone, because they address different failure modes.
More in why labels fail so often.