Triangle Calculator

Calculate the area, perimeter, angles and sides of any triangle from any known values.

✓ Free to use ✓ Instant results ✓ Mobile friendly ✓ No sign-up needed

Known Values

Side a (or base)

Side b

Side c (or hypotenuse)

Included Angle (°) for SAS

Area

Perimeter

Hypotenuse / Side c

Angles

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Types of Triangles

Triangles are classified by sides (equilateral, isosceles, scalene) and by angles (acute, right, obtuse). Different formulas apply to each.

How do I find the area of a triangle?+

Area = 0.5 × base × height. If you only know sides, use Heron's formula.

What is a right triangle?+

A right triangle has one 90° angle. You can use Pythagoras (a²+b²=c²) to find unknown sides.