Determining trampoline size allows you to know the correct size of replacement parts needed to keep a worn trampoline safe. The shape of a trampoline will affect the way you take your measurements, but won't change the parts of the trampoline you need to measure. On both round and rectangular trampolines, one location of the trampoline may differ from other locations. Taking the measurements from multiple locations will ensure you have the correct measurements.
Slide the tape measure across the trampoline mat until the end of the tape measure hooks on the outside of the trampoline frame furthest away from you. Stretch the tape measure to the outside of the trampoline frame closest to you. Read the measurement where the tape measure crosses the trampoline frame.
Move to a point on the trampoline 45 degrees away from the location you took the first measurement. Take a second measurement.
Move to a point 45 degrees from the second measuring location. Take a third measurement.
Add the three measurements. Divide the total by three to determine the average measurement.
Hook the end of a tape measure on the outside frame corner on the length of the trampoline frame. Pull the tape measure across the trampoline mat until it crosses the outside of the trampoline frame nearest you. Read the corner length measurement.
Move to the opposite corner. Measure the length of the trampoline frame.
Measure the distance across the outside of the trampoline at both corners of the trampoline's width.
Add both lengthwise measurements and divide the number by two to determine the length of the trampoline frame. Repeat the process with the two width measurements to determine the width of the trampoline frame.