The chest size is measured with a tape measure, under the arms and around the largest part of your chest. Not too tight and not to loose.
The waist size is measured around the narrowest part of your abdomen, generally at the belly button.
The t-shirts’ cut is slightly slim-fit. The fabric has some elasticity, which allows it to fit various morphologies. The men’s model is 1,78m tall (5’10 ft) and wears a S-size, for a tight wear. The women’s model is 1,70m tall (5’7 ft), wears a M-size for t-shirts and a S-size for the tank tops. If you are hesitating between two sizes of women’s t-shirt, don’t hesitate to go for the upper size.
The Ultrasoft t-shirts’ cut is a bit wide. If you like to wear your tees close to the body, you may order a size down.
But don’t worry : if you order a product which is too big or too small for you, you can send it back for a swap.