More info on how to use the F-O-A Spring Rate Calculator can be found here.

Total Wheel Travel (in)
Sprung Weight of corner (lb.)
Distance (dist1, dist3, or dist5) (in)
Distance (dist2, dist4, or dist6) (in)
Droop %
Spring angle from vertical (Degrees)
Spring Rates (lb./in)

Main Tender  
Individual Spring Rates (lb./in)
Primary Spring Rate (lb./in)

If you wish to re-calculate, change either the Main or the Tender Spring Rates and click Re-Calculate.