Enter any 3 values (at least one side) for a triangle — side a, side b, side c, angle A, angle B, or angle C — and the Triangle Calculator solves for all missing sides and angles, plus area, perimeter, and height. Works with degrees or radians, and handles all triangle types: right, oblique, equilateral, isosceles, and scalene.
Area
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Perimeter
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Side a
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Side b
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Side c
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Angle A (°)
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Angle B (°)
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Angle C (°)
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Height (from a)
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Triangle Type
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You need to provide exactly 3 values, and at least one of them must be a side length. Providing only angles is not enough because infinitely many similar triangles share the same angles but have different sizes.
These abbreviations describe which combination of sides (S) and angles (A) you know. SSS means all three sides are known; SAS means two sides and the included angle; ASA means two angles and the side between them; AAS means two angles and a non-included side; SSA (the ambiguous case) can yield zero, one, or two solutions.
The Law of Sines states that a/sin(A) = b/sin(B) = c/sin(C). It relates each side of a triangle to the sine of its opposite angle and is used to solve triangles when you know an angle-side pair plus one additional value.
The Law of Cosines generalizes the Pythagorean theorem: c² = a² + b² − 2ab·cos(C). It is used to solve triangles when you know all three sides (SSS) or two sides and the included angle (SAS).
Yes. Select 'Radians' from the Angle Unit dropdown and enter your angles in radians (e.g. π/2 ≈ 1.5708 for 90°). All angle results will also be displayed in degrees for clarity.
The SSA case (two sides and a non-included angle) can sometimes produce two valid triangles, one, or none. This calculator resolves to the principal solution. If the given side opposite the known angle is shorter than the other given side, a second solution may exist.
When the base and height are known, Area = (base × height) / 2. When two sides and the included angle are known, Area = (a × b × sin(C)) / 2. When all three sides are known, Heron's formula is used: Area = √(s(s−a)(s−b)(s−c)) where s = (a+b+c)/2.
This calculator handles all triangle types: equilateral (all sides equal), isosceles (two sides equal), scalene (no sides equal), right (one 90° angle), acute (all angles < 90°), and obtuse (one angle > 90°). Just enter any 3 values including at least one side.