Spring rate converter
Convert spring rates between metric and imperial, and watch a 10 kg weight squash your spring.
That's about the same as a mattress spring. A 10 kg weight would squash it about 9.807 mm.
What it means
How much does it give?
Real springs only follow this straight line within their working range. Past that they bind or take a permanent set.
Every unit
Your spring rate in every unit
Learn
Three things worth knowing
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lbf/in ÷ 5.71 = N/mm
A 400 lbf/in coilover is 70 N/mm. The exact factor is 175.13 N/m per lbf/in.
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Hooke’s anagram
Robert Hooke published his law in 1676 as the anagram ceiiinosssttuv, unscrambling two years later to "ut tensio, sic vis": as the extension, so the force.
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Rate is not stiffness of the car
Wheel rate differs from spring rate because of the suspension geometry. A spring mounted at an angle feels softer at the wheel.
Shortcuts
Popular spring rate conversions
Background
About spring rate
Spring rate is force per unit of squash. Car suspension is quoted in N/mm in Europe and lbf/in in the US, which differ by a factor of about 175.
Hooke’s law ties it together: F = kx, so the squash is simply the force divided by the rate.