Spring Rate Calculator

How to Use the Motorcycle Spring Rate Calculator

Use this spring rate calculator to accurately determine the rate (stiffness) of your motorcycle coil springs. Essential for dialing in suspension performance on custom builds, vintage bikes, or any ride. Just enter your spring's wire diameter, mean coil diameter, number of active coils, and select your spring material for the correct modulus of rigidity. Instantly see results in both N/mm and lbf/in.

• Wire Diameter: Thickness of the spring wire itself.
• Mean Coil Diameter: Measured from the center of the wire on one side to the center of the wire on the opposite side. You can also measure the outside diameter of the coil and subtract the wire diameter.
• Number of Active Coils: Only the coils that compress and support load, not the ground/closed coils at each end. For closed-end springs, subtract 1 to 1.5 coils from the total count.
• Material: Pick the most accurate match for your spring for proper modulus of rigidity.

Tip: For accurate spring rate, measure carefully and count only the active coils. If you’re not sure, contact Choice City Moto, we’re here to help you dial in your suspension!

This calculator uses the proven spring rate formula:
k = [d4 × G] / [8 × D3 × n]
Where k = spring rate, d = wire diameter, G = modulus of rigidity, D = mean coil diameter, n = active coils.

Ideal for motorcycle spring rate calculation, suspension tuning, custom builds, or restorations. Trust your numbers, and ride with confidence!