Spring Constant Calculator

In short Hooke's law says the force a spring exerts is proportional to how far it is stretched: F = kx. A spring that needs 20 N to stretch 0.1 m has a spring constant of 200 N/m, and stores exactly 1 joule of energy at that stretch. The energy is the part worth pausing on, because it is ½kx² rather than kx — stretching twice as far stores FOUR times the energy, not twice, since the force grows as you go and the work is the area under a rising line. That square is why a bow drawn twice as far hits far harder than twice as hard, and why the last few centimetres of any spring are where the energy lives. Add a mass and the same spring gives an oscillation period T = 2π√(m/k), which is 0.6283 s for 2 kg on this spring. Unlike a pendulum, this has no amplitude term at all: a mass on an ideal spring is genuinely isochronous, and that is precisely why mechanical watches moved from pendulums to balance springs. Two practical notes. Springs in parallel add their constants and springs in series halve them, which is the opposite way round from resistors and catches people every time. And Hooke's law is an approximation that is excellent over a small range and simply stops past the elastic limit, where the line bends and the spring does not come back.