Starlight Tools

Suspension Spring Rate Calculator

Calculate a spring rate, effective wheel rate, undamped ride frequency, and static deflection for one front or rear corner. Choose imperial or metric units; inputs stay in this browser tab.

A baseline calculation is not a suspension specification Real suspension behavior also depends on tires, dampers, anti-roll bars, bump stops, geometry through travel, aerodynamics, load cases, fatigue, clearances, and vehicle-control systems. Confirm any hardware or setup change with qualified, vehicle-specific engineering guidance.

Enter vehicle and suspension data

Vehicle and selected corner

Use the vehicle's weight in the setup condition.

Rear share is calculated as 100% minus this value.

Use 50% if left/right corner weights are unknown.

Effective unsprung contribution for this corner.

Spring travel ÷ wheel travel near ride height.

Rate or frequency target

Undamped sprung-mass natural frequency; not a recommendation.

Privacy: values are calculated locally. They are not uploaded, stored, or included in analytics events.

Calculated suspension rates

Spring rate, wheel rate, and ride-frequency formulas

This calculator defines motion ratio as spring travel divided by wheel travel. Because leverage changes both force and displacement, the ratio is squared when converting rate:

wheel rate = spring rate × motion ratio²
spring rate = wheel rate ÷ motion ratio²

Selected corner weight comes from axle distribution and left/right corner share. The effective unsprung amount is subtracted before ride frequency is calculated:

corner mass = vehicle mass × axle share × corner share
sprung corner mass = corner mass − unsprung mass
ride frequency = (1 ÷ 2π) × √(wheel rate ÷ sprung mass)

For the frequency equation, rate is converted to N/m and mass to kg. Static deflection is the sprung corner load divided by wheel rate. Tire compliance, damping, and other suspension springs are excluded.

Motion-ratio warning: some references define motion ratio as wheel travel divided by spring travel—the reciprocal of this page's convention. If your source uses that convention, invert it before entry. Directly measuring small, controlled wheel and spring movements near ride height is usually clearer than relying only on arm lengths.

How to use the spring rate calculator

  1. Choose the known quantity. Use target frequency for a mass-based baseline, target wheel rate for an effective rate at the tire contact-patch end of the suspension, or known spring rate to evaluate an installed spring.
  2. Use setup-condition weight. Include the driver, fuel, fluids, cargo, and other loads that belong in the intended condition. Measured corner weights are better than a nominal brochure weight.
  3. Estimate the selected corner. Enter front distribution and the selected corner's share of that axle. If only axle weights are known, convert them to percentages; use 50% left/right only as an approximation.
  4. Remove effective unsprung mass. Account for the wheel, tire, brake, hub, and appropriate portions of links, shafts, spring, and damper. The exact effective amount depends on component motion.
  5. Measure the ratio near ride height. Enter spring movement divided by wheel movement. Geometry can make this ratio change throughout travel.
  6. Verify the complete system. Check spring travel to coil bind, damper stroke, preload and seating, droop, bump stops, loads, clearances, alignment, tire behavior, damping, and control-system compatibility.

What the results mean

ResultMeaningNot included
Spring rateLinear force per unit spring deflection at the springPreload, coil bind, progressive or dual-rate transitions
Wheel rateMain spring's effective vertical rate at the wheel for the entered ratioTire, anti-roll bar, bump stop, bushing, and chassis rates
Ride frequencyUndamped natural frequency of a simple sprung quarter-car massDamper response, tire stiffness, coupling, pitch, roll, and aero loads
Static deflectionLinear equilibrium deflection from the calculated sprung corner loadPreload position, gas force, friction, installed travel, and nonlinear geometry

Suspension spring rate calculator FAQs

What motion-ratio convention does this calculator use?

Motion ratio is spring travel divided by wheel travel. A spring that compresses 0.80 inch while the wheel rises 1.00 inch has a motion ratio of 0.80. Under the page's idealized linear model, wheel rate equals spring rate multiplied by 0.80 squared.

How do I calculate wheel rate from spring rate?

Multiply spring rate by the square of this page's motion ratio. For example, a 500 lb/in spring at a 0.80 ratio produces 500 × 0.80² = 320 lb/in at the wheel before other elastic elements are considered.

Why does the calculator subtract unsprung weight?

Ride frequency uses the mass supported by the spring. The wheel, tire, hub, brake, and portions of suspension links are not fully supported by it, so an effective unsprung contribution is removed from corner weight.

Can vehicle weight alone determine the correct spring rate?

No. Weight establishes supported mass, but a desired response is still needed. This calculator therefore uses a target ride frequency or target wheel rate, or evaluates a spring rate you already know.

Does wheel rate include the anti-roll bar or tire?

No. The displayed wheel rate is the main spring's effective vertical rate under the stated ratio. Tires, anti-roll bars, bushings, bump stops, helper springs, and structural compliance are not combined into it.

Does the result account for progressive suspension geometry?

No. It is a local linear estimate. Motion ratio and effective spring rate can change through travel, especially with rising-rate linkages, progressive springs, helper or tender spring transitions, bump stops, and component compliance.

Are my vehicle measurements tracked?

No. Calculation happens locally in your browser. This tool does not upload, store, or attach input values to analytics events.

Limits and safety disclaimer

  • The model treats one corner as a linear, undamped, single-degree-of-freedom system. It does not simulate whole-vehicle heave, pitch, roll, load transfer, road inputs, tire dynamics, damping, or transient response.
  • The entered motion ratio is assumed constant and applied to a main linear spring. Separate spring and damper motion ratios, installation angle changes, friction, compliance, progressive springs, and bump stops can change actual behavior.
  • Static deflection is a mathematical equilibrium reference, not an installed ride-height or travel prediction. Preload does not change the rate of a linear spring, but it affects when the spring carries load and the available droop.
  • Spring selection must also consider material and manufacturing tolerances, maximum load and travel, coil bind, buckling, seats, retainers, damper stroke and valving, fatigue life, temperature, corrosion, and applicable vehicle or competition rules.

Engineering and safety disclaimer: Results are educational estimates, not design approval, setup advice, or confirmation that a spring is safe or compatible. An unsuitable suspension setup can reduce tire contact, control, stability, component life, or clearance. Have safety-critical changes checked by a qualified suspension professional or engineer using vehicle-specific data.

Methodology and sources

Last reviewed: August 2, 2026. The calculator uses ideal linear-spring, motion-ratio, static-load, and undamped natural-frequency relationships. The convention is stated explicitly because the reciprocal convention is also common.

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