Spring Constant Calculator

Hooke's law

F = k × x PE = ½ × k × x²

Stretch a spring twice as far, get twice the force but four times the stored energy: the energy is the area under the force line. 50 N stretching a spring 10 cm means k = 500 N/m and 2.5 J stored.

Until it isn't linear

Hooke's law holds up to the elastic limit; past it the spring deforms permanently and the formula quietly stops being true. Real datasheets quote a working range. The law is also the seed of all vibration physics: mass on a spring gives the oscillation every guitar string and building sway model starts from.