Spring Rate Calculator

If you have unmarked springs and want to get a rough idea of what spring rate they are, you can use Eibach's spring rate calculator. This tool is designed for reference purposes only for unmarked helical round wire compression coil springs. See notes below on how to measure your spring. There are many variables which are not represented in these calculations, therefore results are estimates and may vary.

Use decimals instead of fractions. For example 5.5 not 5-1/2

Measured in    Inches    Millimeters

Wire diameter in inches:

Inside diameter in inches:

Number of coils:



Estimated Spring Rate:
Notes: If you're measuring a powder coated spring, for example at 0.430" thick, that's going to yield a different spring rate than if you compensated for the powder coat by deducting 0.004" to 0.012" in your coil thickness. Instead of inputting 0.430" for the coil thickness, try 0.418" to compensate for the thickness of the powder coat.

For the number of coils, Eibach is counting full 360° loops plus the partial coil at the top. Point the bottom notch towards yourself. The first full 360° loop is coil number 1. Count upward until you get the partial top.

If the bottom notch is pointing at yourself and represents the 6 o'clock position, compare roughly where the top loop ends.

  • 3 o'clock = 25% example 5.25 coils
  • 6 o'clock = 50% example 5.50 coils
  • 9 o'clock = 75% example 5.75 coils
If you have 5 complete 360° loops and the top partial loop ends at 3 o'clock then you'd input 5.25 into the calculator for the number of coils. If it ends at 6 o'clock then you'd input 5.50 and if it ends at 9 o'clock then you'd input 5.75.

How to count the coils on an Eibach spring

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