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Triangle Calculator

Solve any triangle from common combinations like SSS, SAS, ASA, SSA, or right triangles. Find missing sides, angles, area, and perimeter.

Known values

Pick the layout that matches your question, then enter positive lengths and angles in degrees.

Inputs

Side a
Side b
Side c
triangle calculatorright triangle solverlaw of sines and cosines

Solution

Primary solution

Sides (a, b, c)
3, 4, 5 units
Angles (A, B, C)
36.8699°, 53.1301°, 90°
Perimeter
12 units
Semiperimeter
6 units
Area
6 units^2
Inradius / Circumradius
1 units / 2.5 units
Altitudes (h_a, h_b, h_c)
4, 3, 2.4 units

Scaled diagram

ABCcab

How to use this tool

  1. Select the triangle mode (SSS, SAS, ASA/AAS, SSA, or right triangle).
  2. Enter the known sides and angles as positive values, with angles in degrees.
  3. Review the solved sides, angles, area, perimeter, and derived measures. Export if needed.

What this solver computes

  • Missing sides and angles for common triangle input patterns.
  • Perimeter, semiperimeter, area, inradius, circumradius, and altitudes.
  • Two-solution handling for ambiguous SSA cases.

When SSA gives two triangles

  • SSA uses a side-angle-side pattern where the known angle is not included between the known sides.
  • Depending on proportions, this can create two valid placements for one vertex.
  • The solver shows both valid outcomes so you can compare them directly.

FAQ

Do I need specific units?
Any consistent length unit works. If you enter sides in centimeters, perimeter is in centimeters and area is in square centimeters.
Can this solve right triangles too?
Yes. In right-triangle mode, enter both legs and the solver computes the hypotenuse, acute angles, area, and perimeter.
Why does my input show no solution?
The values may violate triangle constraints, such as triangle inequality in SSS or impossible SSA proportions. Adjust lengths or angle and try again.

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