Compression spring calculator
Calculate spring rate, maximum safe load, deflection and solid height for your compression spring. Enter the dimensions and get engineering results instantly.
Formula
Symbols
Worked example
Computed by the same engine as the calculator above, using the form's starting values.
Enter wire diameter, outer diameter, free length and coil count. The calculator applies the Wahl factor and automatically validates spring index and shear stress.
Load limits use the real allowable stress of each catalog material, so the result already tells you whether the design is manufacturable.
Need a quote? Open the same configuration in the full designer for tiered pricing and a technical drawing.
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 spring rate of a compression spring?
It is the force needed to compress the spring by one unit of length, expressed in lbf/in or N/mm. A 57 lbf/in spring takes 57 lbf for every inch of compression, approximately linearly until the coils touch.
How do I make a compression spring stronger?
Increase the wire diameter (the effect scales with the fourth power), reduce the outer diameter, or reduce the number of active coils. Any of the three changes raises the spring rate.
What is solid height?
It is the length of the spring when all coils touch. The spring cannot work past that point, and healthy designs keep clearance between the maximum working deflection and solid height.
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.
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