Spring force calculator
Calculate the force (load) a compression spring exerts and the maximum safe load before the material yields.
Formula
Symbols
Worked example
Computed by the same engine as the calculator above, using the form's starting values.
Force is rate times deflection (F = k·x). Use the designer to simulate specific operating points and see the stress margin.
The calculator also reports solid height and maximum safe deflection, with the Wahl correction applied to the shear stress.
If you know the required force and travel instead, use the required rate calculator to find out which spring to look for.
Quick tuning: more or less force
- Thicker wire
- Smaller outer diameter
- Fewer active coils
- Thinner wire
- Larger outer diameter
- More active coils
How to measure your spring
- Measure the wire diameter (d) with calipers or a micrometer, away from the ends.
- Measure the outer diameter (OD) across the coils. The mean diameter is OD minus d.
- Measure the free length (FL) with no load, end to end.
- Count the total number of coils. Closed and ground ends reduce the active coil count.
- Identify the end type: closed and ground, closed, double closed or open.
Material moduli and density
| Material | Shear modulus G | Elastic modulus E | Density |
|---|---|---|---|
| Carbon steel (MW) | 11.5 × 10⁶ psi (79.3 GPa) | 29.5 × 10⁶ psi (203.4 GPa) | 7.85 g/cm³ |
| Stainless 302 (SS302) | 10.0 × 10⁶ psi (69.0 GPa) | 28.0 × 10⁶ psi (193.0 GPa) | 7.90 g/cm³ |
| Stainless 17-7 (SS177) | 11.0 × 10⁶ psi (75.8 GPa) | 29.4 × 10⁶ psi (203.0 GPa) | 7.81 g/cm³ |
| Stainless 316 (SS316) | 10.0 × 10⁶ psi (69.0 GPa) | 28.0 × 10⁶ psi (193.0 GPa) | 7.98 g/cm³ |
| Oil tempered MB (OT) | 11.2 × 10⁶ psi (77.2 GPa) | 29.5 × 10⁶ psi (203.4 GPa) | 7.85 g/cm³ |
| Chrome silicon (CS) | 11.2 × 10⁶ psi (77.2 GPa) | 29.5 × 10⁶ psi (203.4 GPa) | 7.85 g/cm³ |
| Hard drawn (HD) | 11.5 × 10⁶ psi (79.3 GPa) | 29.5 × 10⁶ psi (203.4 GPa) | 7.85 g/cm³ |
| Phosphor bronze (PB) | 6.0 × 10⁶ psi (41.4 GPa) | 14.9 × 10⁶ psi (103.0 GPa) | 8.86 g/cm³ |
| Beryllium copper (BC) | 7.0 × 10⁶ psi (48.3 GPa) | 18.6 × 10⁶ psi (128.0 GPa) | 8.25 g/cm³ |
| Chrome vanadium (CV) | 11.2 × 10⁶ psi (77.2 GPa) | 29.5 × 10⁶ psi (203.4 GPa) | 7.85 g/cm³ |
Frequently asked questions
What is the formula for spring force?
F = k·x (Hooke's law): force equals the spring rate times the deflection. A 45 lbf/in spring compressed 0.5 in exerts 22.5 lbf.
What limits the maximum load of a spring?
The shear stress in the wire, corrected by the Wahl factor, compared with the material's allowable stress. Exceeding it causes permanent set (the spring loses free length).
Does force stop growing at solid height?
No: at solid height the spring becomes a rigid tube and force rises abruptly. Running into solid damages the spring and the mechanism, so keep design clearance.
Design the spring and get an instant quote
Open the 3D designer, tune the dimensions and see quantity pricing with a technical drawing and stress analysis.
Open in designer