Hypotenuse Calculator
Enter the two legs of a right triangle to get the hypotenuse — the long side opposite the right angle — plus both angles and the area.
- c = √(a² + b²) = √(9 + 16) = √25 = 5
- A = arctan(a ÷ b) = 36.87°, B = 90° − A = 53.13°
Hypotenuse c
5
- Leg a
- 3
- Leg b
- 4
- Hypotenuse c
- 5
- Angles A · B
- 36.87° · 53.13°
- Area
- 6
- Perimeter
- 12
- Height to c
- 2.4
How to find the hypotenuse
- Square each leg: 6² = 36 and 8² = 64.
- Add them: 36 + 64 = 100.
- Take the square root: √100 = 10. The hypotenuse is 10.
If you know one leg and an angle instead, c = leg ÷ sin(opposite angle) — the right triangle calculator handles that case. Everyday uses: ladder length against a wall, the diagonal of a screen or a room, rafter length from run and rise.
Questions people ask
Is the hypotenuse always the longest side?
Yes. It is opposite the largest angle (90°), and the largest side is always opposite the largest angle.
How long a ladder do I need?
If the top must reach 12 ft up and the foot sits 3 ft out (the usual 4:1 safety ratio), the ladder is √(144 + 9) ≈ 12.37 ft.
What is the diagonal of a 12 × 16 ft room?
√(144 + 256) = √400 = 20 ft.