Easy Spring Rate Conversion Guide with Chart & Calculator

When looking to install coilovers or lowering springs, it’s essential that you get the right ones. However, the manufacturers never make things easy for you — which is why some of them display their spring rate in kg/mm, and others show it in lb/in.

It’s the age-old metric vs standard debate, and they throw you right in the middle of it! But, it doesn’t matter if your new coilovers are in imperial when you want metric, all you have to do is convert it.

We’re here to help you out with an easy-to-use coil spring rate conversion chart and calculator so you can get back to ordering ASAP.

Spring Rate Conversion Charts

If you’re not a fan of conversions or simply don’t have the time to do the math — don’t sweat. You can simply use the convenient spring rate conversion charts below.

If you are, however, looking for specific numbers that aren’t on this list, scroll down for our spring rate conversion calculator.

Lb/in to kg/mm

700 lb/in12.5 kg/mm
650 lb/in11.6 kg/mm
600 lb/in10.7 kg/mm
550 lb/in9.8 kg/mm
500 lb/in8.9 kg/mm
450 lb/in8 kg/mm
400 lb/in7.1 kg/mm
350 lb/in6.2 kg/mm
300 lb/in5.3 kg/mm
250 lb/in4.5 kg/mm

Kg/mm to lb/in

16 kg/mm896 lb/in
15 kg/mm840 lb/in
14 kg/mm784 lb/in
13 kg/mm728 lb/in
12 kg/mm672 lb/in
11 kg/mm616 lb/in
10 kg/mm560 lb/in
9.0 kg/mm504 lb/in
8.5 kg/mm476 lb/in
8.0 kg/mm448 lb/in
7.5 kg/mm420 lb/in
7.0 kg/mm392 lb/in
6.5 kg/mm364 lb/in
6.0 kg/mm336 lb/in
5.5 kg/mm308 lb/in

Spring Rate Conversion Calculator

When it comes to converting kg/mm to lb/in or vice versa, all you need to know is that 1 kg/mm equals 56 lb/in.

But if we’re being honest, you’re not always going to remember that useful trick the next time you need it. To help you out of this fix simply type in your measurement into the calculator below!

What Is Spring Rate?

In layman’s terms, spring rate refers to the amount of weight needed to compress a coil spring one inch. This is a critical measurement when deciding what kind of springs or coilovers you need on your vehicle.

If the springs are too stiff, they’ll never compress as you’re driving. But if they’re too loose, you’ll have a ride that sags and doesn’t bounce back as you drive.

Keep in mind that spring rates apply to new springs, as they age, they’ll wear down, which will make them easier to compress.

Finally, you’re not going to find a spring rate chart. Instead, you’re going to find specs, and you’ll need to convert them to work with the tools that you have — that’s where the lowering springs and coilover spring rate conversion charts above come in handy.

Coilover Spring Rates Explained

If you think you can get away with guestimating the right numbers to get the biggest benefit from installing coilovers, you’re in for a rough ride (quite literally). Your best bet is cross-checking your coilover spring rates with an easy conversion chart or calculator.

So, take the easy way out and bookmark this page to come back to whenever you need to complete another conversion!

Having a hard time figuring out if you’ve got the right measurement? Let us know in the comments below! And while you’re here, why not check out some of the other guides and articles that we have on our website?

1 comment

  1. I have a 2015 wrx and am having trouble finding the right spring rate. I am looking for somehting much stiffer but still managable for daily driving. Is 8k stiff enough or should I go up to 10k?

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