TBT Racing · Complimentary Tool

Spring Rate Calculator

Know exactly what any coil spring is rated. Measure three things, get the rate in kg/mm and lbs/in.

Calculate a spring rate

Inner diameter (mm)

Wire diameter (mm)

Active coils

Enter the three measurements above to see the spring rate.

How to measure: inner diameter is across the inside of the coil; wire diameter is the thickness of the wire (use calipers); active coils are the coils that actually compress — count the total and subtract the flat/closed end coils (~1 each end).