GeomBench

Area Calculator

Rectangle and triangle area, side by side.

Width

Height

Rectangle area (w × h)

Triangle area (½ · w · h): 30

What you entered

Width: 10Height: 6

1
Rectangle area
10 × 6= 60
2
Triangle area (same base & height)
½ × 10 × 6= 30

Result

Rectangle area (w × h): 60

With width 10 and height 6, the rectangle area (60) is exactly double the triangle area (30) — a triangle is always half of the rectangle sharing its base and height.

Rectangle and triangle area from the same dimensions

A triangle with the same base and height as a rectangle has exactly half its area, whatever the dimensions.

Width	Height	Rectangle area	Triangle area
4	3	12.00	6.00
6	5	30.00	15.00
8	6	48.00	24.00
10	7	70.00	35.00
12	9	108.00	54.00

The exact halving holds in every row and for every triangle sharing the base and height, whatever its shape - a tall thin triangle and a wide squat one have the same area if base and height match, because the apex can slide sideways without changing either. That is why the triangle formula is half base times height rather than anything involving the slanted sides. Both areas are in square units of whatever unit you enter.

A triangle is always half its rectangle

Any triangle sharing a base and height with a rectangle covers exactly half that rectangle's area — that's why the triangle formula (½·base·height) is literally the rectangle formula divided by two.

Why compare them side by side

Seeing both formulas together makes the relationship between them concrete instead of abstract, which helps when you're estimating material for a gable roof section or a triangular garden bed next to a rectangular one.

Frequently asked questions

What is the formula for the area of a triangle?

Area = ½ × base × height. The height must be perpendicular to the base. Example: base = 10, height = 6 → Area = ½ × 10 × 6 = 30 square units. This works for any triangle, regardless of shape.

Why is a triangle's area half the rectangle's?

Any triangle fits inside a rectangle with the same base and height. The triangle occupies exactly half of that rectangle — draw the rectangle around any triangle and you'll see the leftover corners always equal the triangle itself.

How do I calculate area in acres?

1 acre = 43,560 square feet. Calculate the area in square feet first (length × width for rectangles, ½ × base × height for triangles), then divide by 43,560. A 200×300 ft plot = 60,000 sq ft ÷ 43,560 = 1.38 acres.