A ruler
i would use inches
To measure crank arm length accurately, use a ruler or measuring tape to measure the distance from the center of the bottom bracket to the center of the pedal spindle. This measurement will give you the crank arm length.
You would use meters.
I would use feet
You would answer it with cubic feet
To measure your arm length, stand up straight with your arms relaxed at your sides. Use a measuring tape and extend it from the top of your shoulder (where it meets your neck) down to your wrist bone. Make sure your arm is straight when measuring for accuracy. Alternatively, you can measure from your shoulder to your fingertips for a longer measurement.
meters
You would use either inches or centimeters.
I would use centimetres and millimetres
centimeter
The best method to accurately measure crank arm length is to use a ruler or measuring tape to measure the distance from the center of the bottom bracket to the center of the pedal spindle. This measurement should be taken in millimeters for precision.
Well, honey, you'd want to use good ol' centimeters to measure the length of your arm. It's precise enough to give you an accurate measurement without getting all tangled up in those pesky decimals. So grab a ruler and start measuring, darling!