Measure your spring length with a spring off the trampoline, unstretched, including hooks in millimetres (mm). Then count how many springs your trampoline has. Any replacement needs to be fully attached to your frame.
Now measure from the end of your frame to end of the spring, including the hook. Make sure the spring is attached to the frame, but not to the mat. There should be no tension on the spring in this measurement.
Using this Round Mat Calculator will help eliminate guesswork. Please make sure your measurements are accurate.
Approximating or rounding your measurements will distort the outcome!