How to use this calculator
- Enter geometry and material. Enter wire diameter, mean coil diameter, active coils and material so the spring rate can be calculated.
- Enter the applied force. Enter the load on the spring in the active unit system.
- Enter free length and end type. These set solid height and the buckling check.
- Read deflection and warnings. Read the calculated deflection, travel to solid, corrected stress and buckling verdict.
How it works
Spring deflection is the load divided by spring rate:
x = F / k
The rate is calculated from helical compression-spring geometry:
k = G · d⁴ / (8 · D³ · Nₐ)
where G is shear modulus, d is wire diameter,
D is mean coil diameter and Nₐ is active coil count.
Once the deflection is known, the same operating point is used for the design checks: the force is applied to the Wahl-corrected shear-stress formula, the deflection is compared with travel to solid, and the slenderness check flags buckling risk.
Worked example
Verified against the live calculator
A music-wire compression spring with d = 1.0 mm, D = 10 mm
and Nₐ = 8 has rate about 1.24 N/mm. Under
12.4 N load, deflection is x = 12.4 / 1.24 = 10 mm.
The calculator then checks that this 10 mm deflection stays below solid height and
within the corrected stress allowance.
Frequently asked questions
How do you calculate spring deflection from force?
First calculate spring rate k from the spring geometry, k = G·d⁴/(8·D³·Nₐ). Then deflection is x = F/k, where F is the applied force. This page also checks stress, travel to solid and buckling at that calculated deflection.
Is spring deflection the same as compression?
For a compression spring, deflection is the amount the spring shortens from free length. If a 40 mm free-length spring is loaded to 30 mm long, its deflection is 10 mm.
Why does the calculator need free length?
Free length is not needed to calculate rate, but it is needed to check remaining travel to solid and the buckling slenderness L₀/D.
Can I use this for a nonlinear spring?
No. This assumes a linear helical compression spring over the working range. Conical, variable-pitch or progressive springs need a different load-deflection model.
What if the calculated deflection is past solid height?
The spring would be fully compressed before reaching the entered load. Increase wire diameter, reduce coil diameter, reduce active coils, choose a stiffer material or use a longer spring envelope.
Method & assumptions
- Linear helical compression spring, static load only.
- Fatigue life, set, relaxation and manufacturing tolerances are not included.
- Material values are typical design data; verify supplier data for production or safety-critical springs.