Coil Spring Rate Calculator
Rate of a compression spring from wire, coil diameter and active turns.
d⁴ over D³: tiny wire changes swing the rate hugely. Keep index C between 4 and 12 — below 4 won't coil, above 12 tangles. Grinding ends costs ~2 coils of activity.
Formula
Coil Spring Rate Calculator is a free spring rate for mechanical and machine-design engineers — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Coil Spring Rate Calculator
Rate of a compression spring from wire, coil diameter and active turns. The calculation implements k = G·d⁴/(8·D³·n) (Shigley ch. 10; SMI handbook). d⁴ over D³: tiny wire changes swing the rate hugely. Keep index C between 4 and 12 — below 4 won't coil, above 12 tangles. Grinding ends costs ~2 coils of activity.
How to use Coil Spring Rate Calculator
- 1Enter Wire diameter in mm.
- 2Enter Mean coil diameter in mm.
- 3Enter Active coils.
- 4Enter Shear modulus G in GPa (Music wire 79 · SS302 69 · phosphor bronze 41).
- 5Read Spring rate, Spring index C (D/d) instantly — no submit button needed.
- 6Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Coil Spring Rate Calculator?
- ✓Implements the standard formula — k = G·d⁴/(8·D³·n)
- ✓Reference cited on-page: Shigley ch. 10; SMI handbook
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Coil Spring Rate Calculator use?+
It computes k = G·d⁴/(8·D³·n), per Shigley ch. 10; SMI handbook. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
d⁴ over D³: tiny wire changes swing the rate hugely. Keep index C between 4 and 12 — below 4 won't coil, above 12 tangles. Grinding ends costs ~2 coils of activity.
Is this suitable for machine design coursework?+
Yes — these are the exact Shigley/Machinery's-Handbook formulas, with the substitution shown step by step, so you can follow the worked example into your own calculation sheet.
Is the Coil Spring Rate Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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