Keep your arms slightly bent, with your fingers in your pockets.

Consider adding just a little extra to this length for shirt sleeves. That way, when you reach forward, your sleeves won’t ride up on your arms. [5] X Expert Source David PewProfessional Tailor Expert Interview. 5 January 2021. If you’re measuring for a coat, measure to the point where your wrist starts to widen into your thumb, and do not add any extra. [6] X Expert Source David PewProfessional Tailor Expert Interview. 5 January 2021.

Ask your partner to keep the tape measurer even to keep the measurement accurate.