1. On a fan with an even number of blades, determine the fan diameter by measuring from blade tip to blade tip on a straight line through the fan axis as shown.
2. For fans with either an even or odd number of blades measure from the blade tip to the center of the hub (as shown) and multiply by 2.
3. For all fans, you may use steps 3 and 4. First, measure the hub diameter as shown, and then proceed to step 4.
4. Measure the length of one blade from tip to base. Be sure to measure from just above the blade root, as shown, OR from where the blade meets the hub in an assembled fan. Multiply the blade length by two and add that measurement to the hub diameter from step 3 to determine your total fan diameter.