Calculate the area of a triangle in square feet. Enter base and height, three sides (Heron's formula), or two sides with an included angle. Converts between sq ft, sq in, sq yd, sq m, and acres.
Calculating the square footage of a triangle is essential for construction, landscaping, flooring, and real estate projects where triangular areas need to be measured accurately. Whether you're working with a triangular garden bed, a gable wall, a sail shade, or an oddly shaped room, knowing the exact area in square feet lets you estimate materials and costs with confidence.
This Square Feet of a Triangle Calculator supports three calculation methods. The simplest uses base and height—just multiply and divide by two. When you know all three sides but not the height, Heron's formula computes the area from the semi-perimeter. And if you have two sides with the included angle, the trigonometric formula ½ × a × b × sin(C) gives you the answer instantly.
Input dimensions in feet, inches, yards, meters, or centimeters, and the calculator converts everything to square feet automatically. Results are also displayed in square inches, square yards, square meters, square centimeters, and acres so you can compare across unit systems. Eight presets for common triangle sizes let you explore results immediately, while reference tables show areas for standard triangles and unit conversion factors. Visual bars provide an at-a-glance comparison of your triangle's area across different unit systems.
Triangle area problems often become inconvenient not because the formula is hard, but because the available measurements vary from job to job. Sometimes you have base and height, sometimes three sides from a field sketch, and sometimes two sides plus an angle from a corner layout. This calculator lets you work from whichever set of measurements you actually have, then converts the result into square feet and other common units for estimating materials, checking plans, or comparing alternate measurement methods.
Base & Height: A = ½ × base × height. Heron's: A = √[s(s−a)(s−b)(s−c)] where s = (a+b+c)/2. Two sides & angle: A = ½ × a × b × sin(C). All dimensions converted to feet before calculation.
Result: ½ × 20 × 15 = 150 sq ft
A triangle with base 20 ft and height 15 ft has area = ½ × 20 × 15 = 150 sq ft. That equals 21,600 sq in, 16.67 sq yd, or 13.94 sq m.
The formula A = ½ × base × height gives the area of any triangle when both dimensions are in feet; the result is directly in square feet. The height must be perpendicular to the base—a slanted measurement along a side will overestimate the area. For triangular garden beds, gable walls, or irregular land sections, measure the base along one edge and drop a vertical from the opposite vertex to obtain the true perpendicular height.
When height is inaccessible, Heron's formula recovers area from three side lengths: compute the semi-perimeter s = (a + b + c) / 2, then Area = √[s(s−a)(s−b)(s−c)]. This is ideal for surveys where three tape measurements are easier than a perpendicular height. The two-sides-and-included-angle method (A = ½ × a × b × sin C) suits fence-corner measurements where you know two fence lengths and the angle between them with a protractor or total station.
Mixing units is the most common source of error. Convert all dimensions to the same unit before computing. Key linear conversions: 1 ft = 12 in, 1 yd = 3 ft, 1 m ≈ 3.28084 ft. Area conversions (square the linear factor): 1 sq ft = 144 sq in, 1 sq yd = 9 sq ft, 1 sq m ≈ 10.764 sq ft, 1 acre = 43,560 sq ft. When working in meters, either convert the linear measurements to feet first, or compute in sq m and multiply the result by 10.764 to get sq ft.
When ordering flooring, tile, or fabric for a triangular area, calculate the exact area first, then add 10–15% waste for cuts and alignment—especially for tile patterns where edge cuts are inevitable. For wood flooring in a triangular bay window, mark the triangle with tape, measure base and apex height at right angles, and apply the base-height formula. Landscaping mulch typically covers 12–18 sq ft per bag at a 2-inch depth; divide the triangle area by the per-bag coverage to determine quantity. For roofing a triangular gable end, add 15–20% waste because of the steep diagonal cuts along the rake edge.
Multiply the base by the perpendicular height and divide by 2. If the base is 20 ft and the height is 10 ft, the area is 100 sq ft.
Heron's formula calculates the area from three side lengths: A = √[s(s−a)(s−b)(s−c)], where s is the semi-perimeter (a+b+c)/2. Understanding this concept helps you apply the calculator correctly and interpret the results with confidence.
Yes. Select "Meters" as the unit and the calculator converts to square feet automatically using the factor 1 m = 3.28084 ft.
1 square meter equals approximately 10.764 square feet.
The formula ½ × base × height requires the height to be at a right angle to the base. A slant height will overestimate the area.
Use the formula A = ½ × a × b × sin(C), where C is the angle between sides a and b. This calculator handles the conversion automatically.