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Spring Rate Conversion Chart & Calculator

Spring Rate Conversion Chart & Calculator

So you’ve decided you want an aftermarket suspension for your car or truck but can’t decide on which brand or which model to get because there are so many variations not in just features but also specs such as one of the most important ones – spring rates.

When looking at spring rates you often times need a spring rate conversion chart or a spring rate calculator to convert from either lb / in (pounds per inch) or kg / mm (kilograms per millimeter). Spring rates are essentially how stiff or how soft the spring is. Spring rates also allow you to customize your handling by adjusting for a firmer or softer spring rate in the front or rear to fine tune your balance.

For a quick and each spring rate conversion chart from lb/in to kg/mm (or vice versa), see below:

700 lb/in = 12.5 kg/mm
650 lb/in = 11.6 kg/mm
600 lb/in = 10.7 kg/mm
550 lb/in = 9.8 kg/mm
500 lb/in = 8.9 kg/mm
450 lb/in = 8 kg/mm
400 lb/in = 7.1 kg/mm
350 lb/in = 6.2 kg/mm
300 lb/in = 5.3 kg/mm
250 lb/in = 4.5 kg/mm

Convert spring rate values easily

Above, we show you the most popular conversion metrics that make up 99% of coilover and spring setups. To get a bit more granular, you can see the kg/mm to lbs/in conversion below, which goes all the way to 16 KG/MM (super stiff!) to 2.0 KG/MM (super soft)

16 = 896
15 = 840
14 = 784
13 = 728
12 = 672
11 = 616
10 = 560
9.0 = 504
8.5 = 476
8.0 = 448
7.5 = 420
7.0 = 392
6.5 = 364
6.0 = 336
5.5 = 308
5.0 = 280
4.5 = 252
4.0 = 224
3.0 = 168
2.0 = 112

quick reference chart

What Spring Rates should I get?

Having a spring rate converter is great, but what does this all mean? We hope you use this conversion chart to get a basis of all of the different coilover and lowering springs out there. For example, let’s say you have a Nissan 350Z and you want to get coilovers. Make a list of the brands in your budget that you are considering and write down their spring rates and other features. Then compare the spring rates between them to get a general idea of which ones are more or less stiff, which affects handling and ride.

It’s true that some spring rates don’t compare directly between brands because some brands have different shock valving adjustments and that makes the spring rates affect the ride and handling differently. We always recommend speaking with a professional tuner on your specific goals with your car and they can help you determine what spring rates you need.


We’d love to start a discussion – what spring rates do you have on your car or truck and what brand coilovers? Did you go with the default spring rates or did you get them custom? Did you get swift springs? Comment below!

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