Physics

Spring Calculator

Find the rate of a helical compression spring.

Shear modulus (GPa)

Wire diameter

Mean coil diameter

Active coils

Calculated Output

Spring rate (N/mm) 2.478

Formula: k = G·d⁴ ÷ (8·D³·n)

Step-by-Step Breakdown

1. Values used:

2. Shear modulus = 79.3 GPa

3. Wire diameter = 2

4. Mean coil diameter = 20

5. Active coils = 8

7. Spring rate = 2.478N/mm

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The math behind it

k = G·d⁴ ÷ (8·D³·n). Thicker wire stiffens dramatically (d⁴); larger coils soften it (D³).

Steel, 2 mm wire, 20 mm coil, 8 coils → about 0.99 N/mm.

How to make a stiffer spring?

Use thicker wire, a smaller coil diameter or fewer active coils.