Nobody knows, which is the problem
There is no published benchmark for AI body measurement accuracy stratified by body size or shape. So claims in either direction are unproven.
That absence is itself the finding. If a provider asserts universal accuracy, there is no study behind it.
The documented concerns
Several independent lines point the same way without quantifying it.
A leading 3D scanning provider told Apparel Resources in 2019 that very large bodies make clean arm and leg separation difficult, which is needed for good measurement extraction. That is a vendor describing a limitation of their own system.
Manual waist measurement error grows with waist size, noted across several studies of waist circumference reliability in larger bodies.
Validation datasets skew young and lean. Researchers explicitly warn that larger, shorter or taller participants affect measurement variability, and one study noted its own sample was young Swiss men only.
Where the effect is measurable
Not in the AI, but in the charts. Research on over 1,000 UK garments found chart accuracy fell from 71% at UK 8-10 to 54% at UK 20-22.
And shoppers report it directly: 46% of plus-size respondents in a 2025 survey cited sizing inconsistencies, against 34% of mid-size and 25% of straight-size shoppers.
The measurable problem for larger bodies is chart accuracy, not measurement accuracy. That distinction matters for where you should place your trust.
The model constraint
Statistical body models average toward the training population. A shape space built on ten principal components capturing 96.6% of variance does well for typical bodies and less well for unusual ones.
Practical guidance
- Treat universal accuracy claims as unproven rather than false.
- Verify the waist manually, since error there grows with size.
- Expect brand charts to be least reliable at larger sizes.
- Rely on your own recorded measurements rather than an inferred size.
- Use fit reviews from similarly-sized shoppers.
What would settle it
A published benchmark stratified by body size. It would be genuinely valuable and would let buyers evaluate tools properly. Its absence is the reason this remains unresolved.
Related: plus-size specifics and the chart data.