They help in a specific, bounded way
Measurements eliminate the question “am I a medium?” That question causes a large share of avoidable returns, and removing it is worthwhile.
They do not eliminate the question “is this brand honest?”
Where the fit decision actually breaks
Look at the two independent failure points. You might be uncertain about your body, or the brand might be wrong about its garment. Measurements only address the first.
And the second is substantial. 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.
Knowing your waist exactly does not help if the brand has mislabelled the garment. Both errors are real and only one is yours.
What measurements genuinely fix
- Choosing between two sizes when you sit between them.
- Ordering from an unfamiliar brand without guessing.
- Reordering from a brand you have already calibrated.
- Communicating with a tailor.
The workflow that produces results
- Measure once, properly, and store permanently.
- Compare against the brand chart, adding ease for the garment type.
- Note the offset you find for that brand.
- Apply it forever after.
After a few brands you have a private fit map, and fit stops being a gamble.
The remaining problem
Ease. Charts rarely publish how much a garment allows, and NMSU Extension specifies 3 to 4 inches on the bust and 1 to 2 inches from nape to waist. Without that number you cannot compute the finished fit.
For stretch knit it gets stranger still, with negative ease of minus 2 inches being normal.
Add fit reviews
Measurements cover your body. Reviews cover the garment, which is the half you cannot control. That is the combination that actually works.
Deeper reading in using measurements online and why labels fail.