Right Triangle Calculator

Enter two sides of a right triangle to find the third side, both angles and the area.

Angle A is opposite leg a

Result

Enter values and press Calculate to see the result.

Formula

tan⁡A=ab,sin⁡A=ac\tan A = \frac{a}{b},\quad \sin A = \frac{a}{c}

SOH CAH TOA relates the angles to the sides.

A+B=90∘A + B = 90^\circ

The two acute angles of a right triangle add up to 90°.

How to use this calculator

  1. Choose which sides you know and enter them.
  2. Angle A is opposite leg a; angle B is opposite leg b.

Worked example

Legs 3 and 4

c = √(9 + 16) = 5.

A = tan⁻¹(3/4) ≈ 36.869898°, B ≈ 53.130102°, and the area is ½ × 3 × 4 = 6.

Frequently asked questions

Can I solve a triangle from an angle and a side?

Yes — use the Triangle Solver, which solves any triangle from three sides (SSS), two sides and the angle between them (SAS), or two angles and a side (ASA).

Why are the angles decimals?

Inverse trigonometric values are usually irrational, so they are rounded.

Learn more