FREE · VISUAL · STEP BY STEP

Triangle Calculator & Solver

Solve any triangle from the information you know. Calculate sides, angles, area, perimeter, heights, medians, radii, and triangle centers with clear step-by-step solutions.

✓ SSS · SAS · ASA · AAS · SSA ✓ Right Triangle Solver ✓ Interactive Triangle

TRIANGLE SOLVER

Enter the information you know

Choose a problem type and enter the known sides and angles. The calculator determines the rest automatically.

Side unit

Sides

Side a opposite A

Side b opposite B

Side c opposite C

Angles

Angle A opposite a

Angle B opposite b

Angle C opposite c

SOLUTION

Triangle Results

CLASSIFICATION

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PERIMETER

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SEMIPERIMETER

—

Sides

a —

b —

c —

Angles

A —

B —

C —

VISUALIZATION

Interactive Triangle

Turn on edit mode and drag any vertex to change the triangle interactively.

Incircle Circumcircle Centers

Edit Triangle Drag vertices

G Centroid I Incenter O Circumcenter H Orthocenter

GEOMETRY

Triangle Properties

Altitude to a —

Altitude to b —

Altitude to c —

Median to a —

Median to b —

Median to c —

Inradius r —

Circumradius R —

Longest side —

SPECIAL POINTS

Triangle Centers

Centroid

Intersection of the three medians.

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Incenter

Intersection of the three angle bisectors.

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Circumcenter

Center of the circumcircle.

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Orthocenter

Intersection of the three altitudes.

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EXPLANATION

Step-by-Step Solution

REFERENCE

Triangle Formulas

Area

A = \frac{1}{2} b h

Half the product of a base and its corresponding height.

Heron's Formula

A = \sqrt{s (s - a) (s - b) (s - c)}

Calculates the area when all three side lengths are known.

Law of Cosines

c^{2} = a^{2} + b^{2} - 2 a b cos C

Used to find an unknown side or angle, especially in SAS and SSS problems.

Law of Sines

\frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C}

Relates each side of a triangle to the sine of its opposite angle.

Inradius

r = \frac{A}{s}

The inradius equals the area divided by the semiperimeter.

Circumradius

R = \frac{a b c}{4 A}

The radius of the circle passing through all three vertices.

FAQ

Triangle Calculator FAQ

What information do I need to solve a triangle?

Common cases include SSS, SAS, ASA, AAS and SSA. A complete triangle normally requires three independent measurements, including at least one side length.

Can I solve a right triangle?

Yes. Select Right Triangle and enter any two appropriate side lengths.

Can SSA produce two triangles?

Yes. SSA is the ambiguous case and can produce zero, one, or two valid triangles depending on the measurements.

Can I drag the triangle?

Yes. Turn on Edit Triangle and drag any of the three vertices. The calculator immediately recalculates the triangle.

What is Heron's formula used for?

Heron's formula calculates the area of a triangle when all three side lengths are known.

Triangle Calculator & Solver

Enter the information you know

Sides

Angles

Triangle Results

Sides

Angles

Interactive Triangle

Triangle Properties

Triangle Centers

Centroid

Incenter

Circumcenter

Orthocenter

Step-by-Step Solution

Triangle Formulas

Area

Heron's Formula

Law of Cosines

Law of Sines

Inradius

Circumradius

How to solve a triangle

Triangle classification

Triangle inequality

Triangle Calculator FAQ