Hooke’s Law Calculator

Fill in any two of spring constant, extension and force, and leave the third blank.

This result is an estimate only. Double-check important figures before relying on them.

How it is calculated

Force F = k × x
Spring constant k = F ÷ x
Extension x = F ÷ k
Stored energy = ½ × k × x²

For the basic law of motion, see the force calculator.

Worked example

A spring with k = 200 N/m stretched 0.05 m:

F = 200 × 0.05 = 10 N
Energy = ½ × 200 × 0.05² = 0.25 J

Why your number may differ

Hooke’s law only holds while the spring is within its elastic limit. Past that point the spring deforms for good and the straight-line relationship breaks.

Frequently asked questions

What is Hooke’s law?

The force a spring exerts is proportional to how far it is stretched or compressed: F = kx, as long as it stays within its elastic limit.

What is the spring constant?

It measures stiffness, in newtons per metre. A bigger value means a stiffer spring.

How is the stored energy found?

Elastic energy = ½ × k × x², in joules.