Compare with a shirt you own, or measure your body. Use one method.
1. Measure a shirt you own
Lay it flat. Measure across the chest from one armpit to the other. If shown in the size chart, also check shoulder width and sleeve length.
For tops: chest, shoulders, sleeve length. For pants: waist, hip, inseam.
2. Measure your body
Wrap the tape around your chest, waist, or hips. Keep it level and comfortable, not tight. Enter these in the body fields.
A body measurement goes around you. A shirt measurement goes across the shirt. If a size chart measurement is unclear, leave it blank.