Use a flexible measuring tape or a ruler
Measure hand length from the base of the palm to the tip of the middle finger
Measure hand width across the widest part of the palm, excluding the thumb
Measure hand circumference around the knuckles with the fingers together and the thumb excluded
Keep the hand relaxed and flat for length and width measurements
Keep the hand slightly open for circumference measurement
Measure both hands and use the larger one
Record the measurements in inches or centimeters
Repeat the measurements for accuracy