Hooke's law spring calculator
Pick the unknown and enter the other two values. Extension is how far the spring is stretched or squeezed from its natural length.
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How to use it
- Enter what do you want to find?, spring constant k, extension x and force f.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
F = k × x, k = F ÷ x, x = F ÷ k, and stored energy E = ½ × k × x².
Example
Inputs: What do you want to find? = Force, Spring constant k = 200 N/m, Extension x = 0.05 m, Force F = 10 N. Result: Spring force: 10 N; Stored elastic energy: 0.25 J.
Limits and caveats
- Hooke's law holds only within the elastic limit; beyond it the spring deforms and does not return.
- Assumes an ideal, massless spring.
Questions about this tool
What does the spring constant mean?
It is the force needed to stretch the spring by one meter. A higher constant means a stiffer spring.
How do I measure a spring constant?
Hang a known mass, measure the extension, then divide its weight (mass × 9.81) by the extension in meters.
Does it work for compression?
Yes. Within the elastic limit squeezing behaves like stretching; enter the compression as a positive number.