Place your tape measure under your arms and measure
the fullest part of your chest. Keep the tape
parallel to the floor. Avoid pulling it too tight.
Measure the length of your shirt from the top, back
of neck to the bottom of the shirt. This should be
done with a shirt flat on a table, not while
Shirt Body Width
Measure the width of a shirt from side-seam to
side-seam while laid flat, not while wearing.