Calculate a triangle’s area from a base and its perpendicular height. Choose US or metric input units and see the result in square feet, square yards and square meters. This is a geometric area calculator, not a material order, structural design or cost estimate.
Triangle area from base and height
Height meets the base line at a right angle (90 degrees). A sloping side is not the height unless it is perpendicular to the selected base. Both values use the selected unit. Changing units or systems clears the inputs.
Triangle area formula
Area = base × perpendicular height ÷ 2. Use the same length unit for both measurements. The resulting area uses the square of that unit. A base of 10 feet and perpendicular height of 6 feet gives 10 × 6 ÷ 2 = 30 square feet.
Which measurement is the height?
Height is the perpendicular distance from the opposite vertex to the line containing the chosen base. The foot of that perpendicular may lie outside the base segment for an obtuse triangle. Do not substitute the length of a sloping side. This tool does not infer height from three sides or from an angle.
US and metric conversion
NIST defines the inch as exactly 25.4 millimeters and gives 0.9144 meters per yard, with 36 inches per yard.1 This tool uses 0.0254 meter per inch, 0.3048 meter per foot and 0.9144 meter per yard. Length conversion factors are squared for areas: square feet = square meters ÷ (0.3048 × 0.3048).
Triangle area chart
Calculated examples for stated bases and perpendicular heights, not recommended dimensions or product coverage.
| Base | Perpendicular height | Area |
|---|---|---|
| 4 ft | 3 ft | 6 sq ft |
| 6 ft | 4 ft | 12 sq ft |
| 8 ft | 5 ft | 20 sq ft |
| 10 ft | 6 ft | 30 sq ft |
| 12 ft | 8 ft | 48 sq ft |
| 20 ft | 10 ft | 100 sq ft |
Worked examples
- 10 ft base, 6 ft height: 30 sq ft = 3.333333333 sq yd = 2.7870912 sq m.
- Equivalent metric input: 3.048 m base and 1.8288 m height produces the same 2.7870912 sq m and 30 sq ft.
- 24 in base, 12 in height: 144 sq in, or 1 sq ft. Divide square inches by 144 to get square feet, not by 12.
- 3 m base, 4 m height: 6 sq m, or about 64.5834625 sq ft. These are base and perpendicular height, not necessarily two arbitrary sides.
Area is not a material order
The result covers one flat triangle. It does not include depth, overlap, cuts, gaps, thickness, waste or package yield. Adding areas is valid only when the shapes do not overlap, or when overlap is subtracted separately. A triangular outline does not by itself define a suitable structure or product layout.
For rectangles, use the square footage calculator. For circular outlines, use the circle area and circumference calculator. Convert fractional inches with the fraction to decimal inches calculator before entering a decimal measurement.
Source and method
1 NIST: SI Units - Length, checked November 3, 2026. NIST supports the unit conversion factors. The triangle formula, chart and worked examples are arithmetic for this calculator.