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Triangle Calculator

Solve any triangle given sides and/or angles. Supports SSS, SAS, ASA, AAS, and right triangle. Shows all missing sides, angles, area, and perimeter.

Solve By
Side a
Side b
Side c
Angle A
Angle B
Angle C
Area
Perimeter
Frequently Asked Questions
How do I calculate triangle area?

Area equals 0.5 times base times height. With three sides use the Heron formula: Area equals the square root of s times (s-a) times (s-b) times (s-c) where s equals half the perimeter.

What is the Pythagorean theorem?

For right triangles: the square of the longest side equals the sum of squares of the other two sides.

What types of triangles exist?

By sides: equilateral (all equal), isosceles (two equal), scalene (none equal). By angles: acute, right, obtuse.

How do I find a missing angle?

All three interior angles sum to 180 degrees. Subtract known angles from 180 to find the missing one.

What is the sine rule?

Each side divided by the sine of its opposite angle gives the same ratio. Use it with two angles and one side.