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Spring Rate Converter — N/m, N/mm, lb/in, kgf/mm

Convert a spring rate value between any combination of N/m, N/mm, kN/m, kN/mm, lb/in, kgf/mm, kgf/m and daN/mm. All conversions route through N/m as the SI base unit.
The spring rate you want to convert

From unit

In N/m (SI base unit)
10,000N/m

All spring rate units converted via N/m as the SI base

N/m
10,000 N/m
N/mm
10 N/mm
kN/m
10 kN/m
kN/mm
0.01 kN/mm
lb/in
57.1015 lb/in
lbf/in
57.1015 lbf/in
kgf/mm
1.0197 kgf/mm
kgf/m
1,019.72 kgf/m
daN/mm
1 daN/mm
N/m10,000 N/m
N/mm10 N/mm
kN/m10 kN/m
lb/in57.1015 lb/in
kgf/mm1.0197 kgf/mm
Step by step
  1. 1

    Conversion factor: 1 N/mm in N/m

    1,000
  2. 2

    Value in N/m: value × factor

    10 × 1,000 = 10,000
Results are estimates for general information only and are not professional advice — always verify important results independently before relying on them. Read the full disclaimer.
Quick answer

How does this calculator work?

Enter a spring rate value and its unit; the converter outputs it in N/m, N/mm, kN/m, kN/mm, lb/in, kgf/mm, kgf/m and daN/mm simultaneously. Key factors: 1 N/mm = 1,000 N/m; 1 lb/in = 175.127 N/m; 1 kgf/mm = 9,806.65 N/m.

Formula
k [target] = k [source] × (factor_source / factor_target) where factors are in N/m
How this is calculated

Spring rate (stiffness) has an SI unit of N/m — one newton of force per metre of deflection. In practice, engineers and manufacturers use a wide range of units depending on their industry and region: automotive suspension engineers often work in N/mm or kN/m; imperial-system users work in lb/in or lbf/in; and traditional mechanical datasheets may list kgf/mm.

Every conversion uses N/m as the pivot unit. The key relationships are: 1 N/mm = 1,000 N/m; 1 kN/m = 1,000 N/m; 1 lb/in = 175.127 N/m (derived from 1 lbf = 4.44822 N and 1 in = 0.0254 m); 1 kgf/mm = 9,806.65 N/m (derived from 1 kgf = 9.80665 N and 1 mm = 0.001 m).

The converter displays all supported units simultaneously so you can read off whichever value your target application needs without running separate conversions.

Frequently asked questions

1 lb/in = 175.127 N/m = 0.175127 N/mm. Equivalently, 1 N/mm ≈ 5.710 lb/in. These factors come from 1 lbf = 4.44822 N and 1 inch = 25.4 mm.

They are numerically equal: 1 N/mm = 1,000 N/m = 1 kN/m. So a spring rate of 50 N/mm is the same as 50 kN/m. The choice of unit is a convention — N/mm is common in mechanical/manufacturing contexts, kN/m in structural and civil engineering.

Multiply by 9.80665, the standard gravity acceleration in m/s². For example, 2 kgf/mm = 2 × 9.80665 = 19.613 N/mm. This is exact within the definition of the kilogram-force (1 kgf = 9.80665 N).

Also known as

spring rate unit converter
n/mm to lb/in converter
kn/m to n/mm
spring stiffness unit conversion
lb per inch to newtons per meter
kgf/mm to n/mm converter

APA

TG we-Calculate Editorial Team. (2026). Spring Rate Converter — N/m, N/mm, lb/in, kgf/mm [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/spring-rate-converter

Chicago

TG we-Calculate Editorial Team. "Spring Rate Converter — N/m, N/mm, lb/in, kgf/mm." TG we-Calculate. 2026. https://we-calculate.com/calculator/spring-rate-converter.

IEEE

TG we-Calculate Editorial Team, "Spring Rate Converter — N/m, N/mm, lb/in, kgf/mm," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/spring-rate-converter

BibTeX

@misc{wecalculate_spring_rate_converter, title = {Spring Rate Converter — N/m, N/mm, lb/in, kgf/mm}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/spring-rate-converter}}, year = {2026}, note = {TG we-Calculate} }

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