Enter what you know, leaving one variable blank, then click Calculate.
Most calculators make you do the algebra yourself, then hand you a bare number. ( for short) works the other way: each of its 687 solvers can find any variable in its formula (2,317 rearrangements, ready to go), so you skip the algebra, and the answer arrives in your choice of units with its work underneath.
Solve for anything
Fill in what you have and leave the unknown empty. Need the radius from an area, or the launch speed from a stopping distance? Same page, nothing to rearrange.
Units are handled
Mix inches with metres, gpm with litres per second, °F with kelvin. Whatever you have in front of you is fine: the site knows 357 units across 78 quantities, and it shows the conversion as its own step so you can check it.
The work is shown
No mystery numbers. The answer unfolds the way you'd write it out by hand: the formula rearranged, your values plugged in with their units, the conversion, the result. Then the same answer again, in every other unit you might want it in.
For students, trades, and 'the experts'
Students settle whose answer is right and keep learning. Trades get the dose, the flow, or the pressure drop in field units, on a phone, between tasks. And the experts? Even when you know the formula cold, it beats the back of an envelope.
Try it The solver below is live. Put 3 in a, 4 in b, leave c empty, and press Calculate. Then flip the metric/imperial toggle and watch the whole calculation redo itself in the other system; below the answer, c is already listed in every length unit there is. When you're done playing, all 687 solvers are one click away.
Pythagorean Theorem
Enter your known values, leave one input blank, and solves for the missing one. Try different units for next level excitement!
One answer feeds the next
Real problems are rarely one formula. You work out a flow rate to get a velocity, to get a Reynolds number, to get a friction factor, to get a pressure drop — and every step depends on the one before it.
Example Problems run that whole sequence on one page. Each step shows the formula it used and the value it carried forward, and every number is editable: change one input and every step after it recalculates. Values travel between steps at full precision, not the rounded figure on screen, so a four-step chain does not quietly accumulate error.
And everything around the formulas
- Unit converters — 78 quantities, one value shown in every unit of its kind at once
- Physical constants — 292 values with their units, uncertainty and where each one came from
- Periodic table — all 118 elements, and their molar masses drop straight into the chemistry solvers
- Formula sets — 70 named groups like the kinematic equations and the gas laws, each with the rule for choosing between them
Learning zone
The Pythagorean theorem says that in any right triangle, the square of the hypotenuse (the side opposite the right angle) equals the sum of the squares of the other two sides. Known to Babylonian surveyors a thousand years before Pythagoras, it remains the working tool of carpenters, pipefitters, and navigators: the 3–4–5 triangle is still how a layout crew squares a foundation.
It only applies to right triangles. If your triangle has no 90° angle, reach for the law of cosines instead.
- = Leg a
- = Leg b
- = Hypotenuse c
Every solver has one. Browse all 687 →