To calculate the square meters of a triangle, you won't need a special measuring device. Square units gauge a triangle's area, the two-dimensional space inside its three sides. After measuring the triangle's sides in meters, you use a triangular area formula to determine the number of square meters in the triangle's area. One such formula is called Heron's formula, and it works for any type of triangle.

## Measure the Sides

Measure all three of the triangle's sides. For an example, assume your triangle's three sides measure 6, 8 and 10 meters.

## Calculate the Perimeter

Add the measurements together to get the perimeter. Then halve that number to determine the semi-perimeter -- 6, 8 and 10 added together equals 24 meters, half of which is 12 meters.

## Subtract the Sides from the Semi-Perimeter

Subtract the three sides separately from the semi-perimeter — 12 - 6 is 6 meters, 12 - 8 is 4 meters and 12 - 10 is 2 meters.

## Multiply the Differences

Multiply the three differences from the prior step, and then multiply that product by the semi-perimeter -- 6 * 4 * 2 equals 48 meters; 48 * 12 equals 576 meters.

## Calculate the Square Root

Calculate the square root of the previous step's final product to find the triangle's area -- the square root of 576 meters is 24, so the area of the triangle is 24 square meters.

#### TL;DR (Too Long; Didn't Read)

If your measurements are standard (feet or yards) rather than metric, you can convert them to metric units using an online conversion program.