🔁 Spring Rate Converter
Convert a spring rate value between N/mm, N/m, lbf/in, and kgf/mm.
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Spring Rate Unit Conversion
Spring rate (stiffness) is expressed in different units depending on region and industry: N/mm and N/m in SI systems, lbf/in in US customary units, and kgf/mm in older metric engineering practice. This tool converts between them using exact unit-conversion factors: 1 lbf/in = 0.175127 N/mm, and 1 kgf/mm = 9.80665 N/mm (since 1 kgf = 9.80665 N).
Enter a spring rate in any of these units and get the equivalent value across all four, useful when comparing spring specifications from different manufacturers or catalogs that use different unit conventions.
Last reviewed August 2026