Math calculator
Area Calculator
Area of rectangles, triangles, circles, trapezoids, and more.
Quick answer
How do you calculate area?
Multiply length by width for rectangles: a 12 ft × 10 ft room is 120 square feet. A triangle is half of base × height (½ × 10 × 6 = 30). A circle is π × radius²: r = 3 gives about 28.27 square units.
Rectangle A = l × w. Square A = a². Triangle A = ½bh. Circle A = πr². Trapezoid A = (a + b)/2 × h. Parallelogram A = bh. Ellipse A = πab. Sector A = (θ/360) × πr².
⚡ Answer updates as you type · Enter = calculate · Esc = reset
- Formula: A = l × w
- Substitute: A = 12 × 10
- A = 120 ft²
- Convert: 120 ft² = 11.1484 m² (1 ft = 0.3048 m, so square it).
Find the area of a rectangle, square, triangle, circle, trapezoid, parallelogram, ellipse, or sector — in square feet, meters, acres, and more, with the formula worked out.
About this Area Calculator
The Area Calculator finds the area of a rectangle, square, triangle, circle, trapezoid, parallelogram, ellipse, or circle sector in mm, cm, m, km, inches, feet, yards, or miles. It also converts the result to square meters, square feet, and acres and gives the perimeter — great for flooring, paint, gardens, land, and geometry homework.
What you'll need
- • Shape
- • Unit
- • Dimensions: length, width, base, height, radius, or angle
How it works
- 1. Choose the shape and unit.
- 2. Enter the measurements shown on the picture.
- 3. The calculator applies the area formula.
- 4. Read the area in square units, m², ft², and acres.
- 5. Check the substituted formula in the steps.
Worked example
A trapezoid garden with parallel sides 8 ft and 12 ft and height 5 ft: A = (8 + 12) ÷ 2 × 5 = 50 ft², about 4.65 m².
Related searches
Area Calculator FAQ
What is the Area Calculator?
The Area Calculator is a free online tool that helps you area of rectangles, triangles, circles, trapezoids, and more.
How do I use the Area Calculator?
Open the Area Calculator, enter the requested values, and review the instant estimate on the page.
Is the Area Calculator free?
Yes. The Area Calculator is free to use on Fast Online Calculator and does not require an account.
How do I find square footage of a room?
Measure length and width in feet and multiply. A 15 ft × 12 ft room is 180 square feet. For L-shaped rooms, split into rectangles and add them.
What is the difference between area and perimeter?
Area is the space inside a shape (square units). Perimeter is the distance around it (regular units).
How many square feet are in an acre?
One acre is 43,560 square feet, or about 4,046.86 square meters.
What if I know the diameter of a circle?
Divide the diameter by 2 to get the radius. A 10 ft diameter circle has r = 5, so A = π × 25 ≈ 78.54 ft².
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