For all measurements use a soft tailor tape measure.
2- Shoulder Width
3- Sleeves Length
When having your bicep measured, your arms should be completely relaxed and hanging loose by your sides.
To ensure that your shirt fits properly, the bicep measurement should be taken around the thickest part of your bicep. This point will probably be high up on your arm, only about 2 inches (5.1 cm) below the armpit.
Insert a finger width.