Triangle Area Calculator
Find the area of a triangle from its base and height, or from the lengths of its three sides.
Reviewed by the WorldCalcs team · Methodology · Last reviewed: June 2026
Area
30
area = ½ × 10 × 6 = 30
What is a triangle area calculator?
A triangle area calculator finds the area of a triangle. It supports the two most common methods: the simple base times height formula, and Heron's formula when you know all three side lengths. This is useful for geometry homework, construction, land measurement and any time you need the space inside a triangle.
How it's calculated
With a base and the perpendicular height, the area is ½ × base × height. When you know all three sides a, b and c, use Heron's formula: first find the semi-perimeter s = (a + b + c) ÷ 2, then area = √(s(s − a)(s − b)(s − c)). The three sides must be able to form a triangle, meaning each side is shorter than the sum of the other two.
Example
A triangle with a base of 10 and a height of 6 has an area of ½ × 10 × 6 = 30. Using Heron's formula on a 3-4-5 triangle: s = (3 + 4 + 5) ÷ 2 = 6, so the area is √(6 × 3 × 2 × 1) = √36 = 6. A 5-5-6 triangle gives s = 8 and an area of √(8 × 3 × 3 × 2) = √144 = 12.
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Results are estimates and may contain errors — for general information only, not professional advice. Always verify before relying on them. Disclaimer
How to use
Choose a mode, then enter the measurements. The calculator updates instantly.
Base and height: area = ½ × base × height. Three sides: uses Heron's formula with the semi-perimeter.