Physics Formulas

Pick a formula, then fill in all but one box: the empty box is worked out. Or tap a letter under Solve for, and the box you were solving keeps its answer while the one you tapped is worked out instead. Every box has its own unit, and the answer is shown in the unit you pick for it.

Every value is changed to SI units first (meters, seconds, kilograms, newtons, joules, watts, volts, amps, ohms), using exact sizes: a mile is exactly 1,609.344 m, a pound exactly 0.45359237 kg, km/h is 1,000 m in 3,600 s. Details shows the formula, the formula rearranged for your answer, your numbers put in with their units, and the answer, with a drawing where one helps.

Some values can’t be found from some others: a time can’t be 0 or below, a mass or a resistance must be above 0, and dividing by 0 has no answer. Square roots of numbers below 0 have no real answer, which in s = ut + ½at² and v² = u² + 2as means the object turns back before it covers the distance. When a time comes out two ways, the first one after the start is shown and both are explained. Use ± to make a value negative, for slowing down or moving the other way.

Gravity g starts at 9.81 m/s², the usual value near the Earth’s surface; change it for the Moon (1.62) or anywhere else. Answers are rounded to 4 significant figures unless you pick 2 to 6. Your formula, values and units are saved on this device only. Clear all empties the boxes in view (g goes back to 9.81), and Undo brings them back.