Enter two side lengths and leave the third blank or set it to 0.
Result updated. hypotenuse c: 5.
Triangle result
Main result from the values entered.
hypotenuse c
With side a = 3 and side b = 4, the hypotenuse c is 5.c = √(a² + b²)
Side a
3
Side b
4
Hypotenuse c
5
Use the same unit for all sides.
How this Pythagorean theorem calculator works
Enter two side lengths for a right triangle and leave one side blank or set it to 0. The calculator rearranges a² + b² = c² to solve the missing side, or checks all three positive sides against the formula.
Finding the hypotenuse vs finding a leg
When c is blank, the calculator finds the hypotenuse with √(a² + b²). When a or b is blank, it subtracts the known leg squared from c squared, then takes the square root.
What this calculator does not include
This calculator only applies to right triangles. It does not solve non-right triangles, draw precise diagrams or replace a full triangle solver.
Key terms and assumptionsShort notes about right triangles, the hypotenuse, units and missing-side validation.
- Right triangles only
- The formula a² + b² = c² applies to right triangles.
- Hypotenuse c
- Side c is treated as the hypotenuse, the longest side opposite the right angle.
- Missing side
- Enter two side lengths and leave the side to calculate blank or set it to 0.
- Unit-agnostic
- Use the same unit for all side lengths. The calculator does not convert units.
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FAQs
What is the Pythagorean theorem?
For a right triangle, the squares of the two legs add up to the square of the hypotenuse: a² + b² = c².
Which side is the hypotenuse?
The hypotenuse is the longest side of a right triangle and is opposite the right angle.
Can I leave any side blank?
Yes. Enter two sides and leave the side you want to calculate blank or set it to 0.
Why does the hypotenuse need to be longest?
In a right triangle, the hypotenuse is always longer than either leg.
Does this work for any triangle?
No. It only applies to right triangles.
Can I use units?
The calculator is unit-agnostic. Use the same unit for all side lengths.
Can I copy the result?
Yes. Copy result includes the solved side and formula.