Spring Rate Calculator
Spring stiffness in N/m and N/mm from a known force and deflection, with the stored energy.
Results
Ratio
12,000.00
N/m
Ratio
12.0000
N/mm
Energy
3.7500
J
What this tool does
A spring's rate is the force it takes to compress or extend it by one unit of length, and within its working range that number stays constant. The stored energy is half the force times the deflection, which is why a spring at double the deflection holds four times the energy.
Formula
k = F ÷ x , E = ½ × k × x²
Variables
| Symbol | Meaning | Unit |
|---|---|---|
f | Force | N |
x | Distance | mm |
k | Ratio | N/m |
km | Ratio | N/mm |
E | Energy | J |
Worked example
- Force300 N
- Distance25 mm
- Ratio12,000.00 N/m
- Ratio12.0000 N/mm
- Energy3.7500 J
Limitations
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.