Chest measurement done correctly and the typical mistake
Short answer: Measure over the fullest point with the tape level across the back. The typical mistake is a tape that slips down at the back and gives a reading that is too small.
How to do it
Stand relaxed with your arms at your sides. Put the tape around the chest at the fullest point and check in the mirror that it lies level all the way round, including across the shoulder blades. Breathe out normally and read the number.
The mistake everyone makes
The tape slips down at the back because the arms are raised while measuring. That gives a reading several centimetres too small, and therefore a size that pulls across the chest. Get help if you can.
What the number is used for
Chest is the main measurement for tops, shirts and undershirts. For a bra you measure both under the bust and over the fullest point, and those are two different numbers. See bamboo bras without underwire.
Always compare with the size chart
Brands cut differently, and a size does not mean the same thing at two manufacturers. Use the number rather than the letter. See bamboo clothing for women and bamboo clothing for men.
Frequently asked questions
Should I measure wearing a bra
Yes, wearing the bra you normally use, otherwise the measurement does not match everyday life.
Should I breathe in
No. Breathe out normally and hold the tape lightly against the body.
What if the chest falls between two sizes
Choose the larger if the fabric has no stretch, and the smaller if it contains elastane.