Enter any two known angles (in degrees °), click calculate, and get the third one automatically.
This tool is based on the Triangle Sum Theorem: the sum of the three internal angles of any triangle is always 180 degrees.
Formula: ∠A + ∠B + ∠C = 180°. If you know two angles, subtract their sum from 180° to find the third.
Works for all triangles: acute, right, and obtuse.
Ensure the sum of the two entered angles is less than 180 degrees.
180 degrees.
A triangle with one 90-degree angle.
Each angle is 60 degrees.
A triangle with one angle greater than 90 degrees.
180 - 50 - 60 = 70 degrees.
∠A + ∠B + ∠C = 180°. If two are known, subtract their sum from 180°.
Enter two internal angles to get the third, useful for geometry homework, teaching and design.
Yes. All inputs are in degrees; this calculator does not accept radians.
The third angle becomes very small. Be careful about measurement errors and triangle validity.
It can be used together with triangle area, trigonometric and side-length calculators.
This tool helps you quickly calculate the third angle of a triangle. Useful for geometry and design.
Scan QR code to use on mobile.