Length 5 m, width 3 m
Area = length × width
5 × 3 = 15 m². For a square with side 3 m, enter 3 as both the length and width to get 9 m².
Geometry and measurement
Area Calculator
Choose a shape, enter its dimensions, and convert the area into the units you need.
Calculate a shape's area
Area
Enter the shape's dimensions, then select Calculate.
Same area in other units
Calculation steps
Your dimensions are processed in your browser and are not sent to a server.
Formulas and worked examples
Base 6 m, perpendicular height 4 m
Area = base × height ÷ 2
6 × 4 ÷ 2 = 12 m². The height must be perpendicular to the chosen base. A sloping side is not usually the height.
Radius 3 m
Area = π × radius²
π × 3² = 9π m² ≈ 28.274334 m². A diameter of 6 m gives the same result because the radius is half the diameter.
Parallel sides 6 m and 10 m, height 4 m
Area = (side A + side B) × height ÷ 2
(6 + 10) × 4 ÷ 2 = 32 m². Average the lengths of the parallel sides, then multiply by the perpendicular height.
Square units, precision, and references
Area conversions use the square of the length conversion factor. Since 1 m = 100 cm, 1 m² = 10,000 cm². Similarly, 1 ft = 12 in gives 1 ft² = 144 in², not 12 in².
Inches, feet, and yards use exact international definitions: 1 in = 0.0254 m, 1 ft = 0.3048 m, and 1 yd = 0.9144 m. An acre here is exactly 43,560 international square feet, or 4,046.8564224 m². A hectare is exactly 10,000 m². Historical U.S. survey-foot units are not used.
Rectangle, triangle, and trapezoid calculations preserve exact fractions throughout multiplication and conversion. Circle calculations preserve the exact coefficient of π and evaluate π with 120 significant digits. Results display 6 decimal places by default; you can select 0, 2, 4, 6, or 10. Rounding is to the nearest value with exact halfway values rounded up. The ≈ mark indicates a rounded result and is always shown for decimal circle areas.
Exact arithmetic cannot make a measurement more precise. For example, a width measured only to the nearest centimeter still has that measurement limit even if the result shows six decimal places.
Unit references: NIST SI Units — Length, NIST SI Units — Area, and NIST exact international-foot conversion factors.
Common questions
Can I enter feet and inches together?
Use one unit for every dimension. For 5 feet 6 inches, enter 5.5 with feet selected, or 66 with inches selected. Text such as 5 ft 6 in is not accepted. The Unit Converter can help convert dimensions before you calculate the area.
What is perpendicular height?
It is the distance measured at a 90-degree angle to the chosen base. For a triangle, it runs from the opposite vertex to the base or its extended line. For a trapezoid, it is the perpendicular gap between the two parallel sides. Measuring along a sloping side gives a different length.
Should I enter a circle's radius or diameter?
Enter the radius. Divide the diameter by two first: a circle 10 cm across has a radius of 5 cm. Entering the diameter as the radius would make the calculated area four times too large.
Can the two parallel sides of a trapezoid be equal?
Yes. Equal positive parallel sides produce the same area formula as a parallelogram: side length × perpendicular height. All required dimensions must be greater than zero; degenerate shapes with zero height or radius are not accepted.
How do I calculate an irregular floor or garden?
Divide a flat outline into non-overlapping rectangles, triangles, circles, or trapezoids. Calculate each part in the same area unit, then add the parts. Subtract holes or cutouts separately. A sloped or curved surface may need different measurements and is outside this calculator's scope.
Why does a tiny area display zero?
A positive area can be smaller than the selected display precision. It will show ≈ and a note with the exact value, including π for circles. Choose a smaller area unit such as mm², or increase decimal places. The underlying area is not replaced with zero.