About the Spring Calculator (Hooke's Law)
Springs stretch or squash in proportion to the force applied, as long as they are not overloaded. This calculator solves Hooke's law for whichever of the force, the spring constant or the stretch you do not know, and gives the energy stored in the spring. Type two of the force, the spring constant and the stretch and the spring force appears at once, with a few related figures underneath, and you can copy the result with one tap. The sums run in your browser, so nothing you enter is uploaded.
Updated October 2026
How to use the Spring Calculator (Hooke's Law)
- 1Enter two of the force, the spring constant and the stretch.
- 2Pick the units or options from the menus if the spring force tool offers them.
- 3Read the spring force in the large result box.
- 4Look at the extra rows for related figures.
- 5Press Copy result to keep the answer.
When you need the spring force
Physics students use it daily, and makers and engineers use it to choose springs for latches, scales and suspensions.
A stiffer spring has a larger k. Springs in parallel add their constants, and springs in series combine like resistors in parallel.
How the spring force is worked out
F = k × x, where k is in newtons per metre and x in metres. Energy = ½ × k × x². A spring of 400 N/m stretched by 0.05 m pulls back with 20 N and stores ½ × 400 × 0.0025 = 0.5 J. A force of 20 N on a 400 N/m spring stretches it 0.05 m.
Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.
- Solve any of three
- Energy stored
- Simple inputs
Mistakes to avoid with spring force
Keep the stretch in metres, not centimetres. Hooke's law fails past the elastic limit, when the spring stays bent. The tool does not check the limit.
On phone and computer
On a phone, type into the boxes one after another and read the spring force underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the spring force move. The spring calculator (hooke's law) works the same on both.
Checking your spring force by hand
A good habit is to test the spring calculator (hooke's law) with a case you already know. A spring of 400 N/m stretched by 0.05 m pulls back with 20 N and stores ½ × 400 × 0.0025 = 0.5 J. A force of 20 N on a 400 N/m spring stretches it 0.05 m.
If your own figures give a surprising answer, repeat the working yourself: F = k × x, where k is in newtons per metre and x in metres. Energy = ½ × k × x². Small differences usually come from rounding, from mixing units, or from a typing slip in one of the inputs. Spring force is just one mechanical sum. Look at pressure with the Pressure Converter, pump work with the Pump Power Calculator, and heat flow with the Heat Conduction Calculator.
Features
- Metres, not centimetres
- Check the elastic limit
- Springs in series and parallel combine
- Clear messages when the spring force inputs make no sense
- Copy the result with one tap
- Private: nothing is uploaded
Frequently asked questions
How do I calculate spring force?
F = k × x, where k is in newtons per metre and x in metres. Energy = ½ × k × x². A spring of 400 N/m stretched by 0.05 m pulls back with 20 N and stores ½ × 400 × 0.0025 = 0.5 J. A force of 20 N on a 400 N/m spring stretches it 0.05 m.
What is the formula for spring force?
F = k × x, where k is in newtons per metre and x in metres. Energy = ½ × k × x². The spring calculator (hooke's law) applies it exactly and rounds only the displayed answer to six significant figures.
What is the spring constant?
The force needed per metre of stretch, in newtons per metre.
Does it work for compression?
Yes, with the same formula.
What happens past the elastic limit?
The spring deforms permanently and the law no longer applies.
Is this spring calculator (hooke's law) free and private?
Yes. It is free, needs no account and runs in your browser, so the numbers you type are not uploaded or stored.