Triangle Solver

Enter any valid combination of sides and angles (SSS, SAS, ASA, AAS, SSA) and solve the remaining parts, area, and perimeter. Calculates in your browser.

Enter known sides and angles; leave the rest blank. Angle A is opposite side a.

Side a · b · c-
Angle A · B · C-
Area-
Perimeter-

Show the math

The laws of sines and cosines solve any triangle from enough parts:

a ÷ sin A = b ÷ sin B = c ÷ sin C

c² = a² + b² − 2ab·cos C

Works with SSS, SAS, ASA, AAS, and SSA inputs. All math runs in your browser.

What this does

A triangle solver takes any valid combination of sides and angles (SSS, SAS, ASA, AAS, SSA) and solves the remaining parts, area, and perimeter.

How to use it

  1. Enter the sides and angles you know.
  2. Match each angle to its opposite side.
  3. Read the solved triangle.
  4. See the area and perimeter.

How it works

It applies the law of sines or law of cosines depending on what you supply. Angle A is opposite side a, and so on.

a ÷ sin A = b ÷ sin B; c² = a² + b² − 2ab·cos C

Understanding your result

Watch the SSA case, two sides and a non-included angle, because it is the ambiguous one: it can yield two valid triangles, one, or none, so confirm which fits your situation. The solver applies the law of sines or cosines from what you supply, and if it reports no solution your inputs cannot form a real triangle, often because the angles do not sum to 180 degrees.

Example

A 3-4-5 triangle solves to a right angle opposite the longest side.

Sources & methodology

Last updated .

Frequently asked questions

How does it solve triangles?

It uses the law of sines (a ÷ sin A = b ÷ sin B) and the law of cosines (c² = a² + b² − 2ab·cos C) depending on what you supply.

Which inputs work?

Any solvable set: SSS, SAS, ASA, AAS, and SSA. Angle A is opposite side a, and so on.

Is my data stored?

No. Everything is calculated locally in your browser.