Triangle area calculator

Calculate triangle area from the base and perpendicular height using A = b × h ÷ 2. Use matching measurement units and get the area in square units.

Result

Different shape, same area

Use the “Drawing shape” menu above to change the figure. The base and height stay the same, so the area does too. The dashed line shows the height perpendicular to the base.

How do you calculate the area of a triangle?

Multiply the base by the perpendicular height and divide by two. Base and height must use the same unit; the result is in square units.

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

Which height should you use?

The height meets the base or its extension at a right angle: it is generally not the sloping side. In an obtuse triangle it may lie outside the triangle. If you know the area, use the inverse formulas to find the base or height. Base and height alone do not determine the perimeter.

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

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

Example: a triangular sail

A sail has a base of 6 m and a perpendicular height of 4 m. Their product is 24 m²; the sail occupies half of this area, or 12 m².

From measurements to area

Input: $b = 6 m; h = 4 m$
Result: $12 m^{2}$

Calculation steps

Multiply the base and height, both measured in metres.
$6 \times 4 = 24 m^{2}$
Divide the product by two to get the sail’s area.
$A = \frac{24}{2} = 12 m^{2}$

How to get the area in square metres

If your measurements are in centimetres, choose m as the result unit to read the area in m². A triangle with a base of 6 cm and height of 4 cm covers 12 cm², equivalent to 0.0012 m². Convert areas using the square of the length conversion factor.

1 m^{2} = 10000 {cm}^{2}

Precision and special cases

Base and height from 0 to 10¹²; input area up to 5 × 10²³ in the chosen units. Results are normally rounded to two decimal places; small values retain useful digits. Zero represents a degenerate figure. The drawing adapts its scale and illustrates the selected shape; it does not reconstruct a triangle from three sides.

If a change of mode or input unit exceeds numerical limits, it is rejected and the previous measurements are kept. Positive values too small to represent are not treated as zero. Edit a measurement or choose another option to resume calculation.

For inverse calculations, area uses the square of the input unit. A known side of zero cannot determine the other side.

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Triangle area calculator

Result

Different shape, same area

How do you calculate the area of a triangle?

Which height should you use?

Example: a triangular sail

From measurements to area

Calculation steps

How to get the area in square metres

You might also need

Triangle perimeter calculator

Regular hexagon area calculator

Regular polygon area calculator