Triangle Calculator

SSS uses the law of cosines for the angles and Heron’s formula for the area. SAS uses the law of cosines to find the missing side and the law of sines to find the remaining angles. ASA uses the law of sines once the third angle is derived from 180° minus the two given angles.

All angles are in degrees, both input and output. The calculator converts to radians internally for the trig functions.

The calculator checks the triangle inequality in SSS mode, and checks that angles are positive and sum to less than 180° in SAS / ASA modes. If the inputs are invalid, you will see an error message in place of the numeric result.