Right Triangle Calculator
Calculate right triangle instantly in your browser.
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What this tool does
Calculate right triangle instantly in your browser. Right triangles only; the two acute angles always sum to 90°.
How to use the Right Triangle Calculator
- Enter or select leg a (enter 0 if unknown).
- Enter or select leg b (enter 0 if unknown).
- Enter or select hypotenuse c (enter 0 if unknown).
- Read the calculated result; change any measurement to compare alternatives.
Formula
Enter any two sides (the third as 0): the missing side comes from a² + b² = c², the angles from inverse trig — A = atan(a/b) — the area is ab/2 and the perimeter is a + b + c.
- a
- Leg a (enter 0 if unknown)
- b
- Leg b (enter 0 if unknown)
- c
- Hypotenuse c (enter 0 if unknown)
Right triangles only; the two acute angles always sum to 90°.
Worked example
For right triangle calculator, the following measurements illustrate the exact method: Leg a (enter 0 if unknown): 3; Leg b (enter 0 if unknown): 4; Hypotenuse c (enter 0 if unknown): 0.
Inputs
- Leg a (enter 0 if unknown)3
- Leg b (enter 0 if unknown)4
- Hypotenuse c (enter 0 if unknown)0
Result
- Leg a3
- Leg b4
- Hypotenuse c5
- Angle A (opposite a, degrees)36.87
- Angle B (opposite b, degrees)53.13
- Area6
- Perimeter12
Results explained
- Leg a
- Leg a from the formula above. Right triangles only; the two acute angles always sum to 90°.
- Leg b
- Leg b from the formula above. Right triangles only; the two acute angles always sum to 90°.
- Hypotenuse c
- Hypotenuse c from the formula above. Right triangles only; the two acute angles always sum to 90°.
- Angle A (opposite a, degrees)
- Angle A (opposite a, degrees) from the formula above. Right triangles only; the two acute angles always sum to 90°.
- Angle B (opposite b, degrees)
- Angle B (opposite b, degrees) from the formula above. Right triangles only; the two acute angles always sum to 90°.
- Area
- Area from the formula above. Right triangles only; the two acute angles always sum to 90°.
- Perimeter
- Perimeter from the formula above. Right triangles only; the two acute angles always sum to 90°.
Frequently asked questions
Enter any two sides (the third as 0): the missing side comes from a² + b² = c², the angles from inverse trig — A = atan(a/b) — the area is ab/2 and the perimeter is a + b + c.
Right triangles only; the two acute angles always sum to 90°.
Where mathematically meaningful, yes. Fields specify permitted ranges and undefined operations display an error.
Exact integer calculations use safe integers; decimal calculations use browser floating point, so small rounding differences can occur.
All values remain in your browser and are never uploaded.