Area Calculator
Calculate the area of common shapes — rectangle, circle, triangle, trapezium, and more.
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What Is a Area Calculator?
This area calculator computes the surface area of common 2D shapes. Select a shape, enter the measurements, and get the result in square units instantly.
Area measures the amount of two-dimensional space inside a boundary. It applies to flooring, painting, gardening, roofing, tiling, fabric cutting, and land measurement. Every shape has a specific formula linking its dimensions to the enclosed space.
Supported shapes include rectangles, squares, circles, triangles, trapeziums, parallelograms, and ellipses. Enter dimensions in any consistent unit — metres, centimetres, feet, or inches — and the result appears in the corresponding square unit.
How Do You Use This Area Calculator?
Select a shape, enter the required dimensions, and click Calculate. The result shows the area with the formula used.
- Select the shape from the dropdown menu.
- Enter the required dimensions in the input fields provided.
- Confirm the measurement unit you are using.
- Click Calculate to see the area result.
- Read the area value and the formula used.
- Click Reset to calculate a different shape.
How Does the Area Calculator Formula Work?
The formula used: Rectangle: L × W. Circle: πr². Triangle: ½ × base × height. Trapezium: ½(a + b) × h
Each shape uses a different formula based on its geometry.
Rectangle = length × width
Square = side × side = side²
Circle = π × radius² (π ≈ 3.14159)
Triangle = ½ × base × height
Trapezium = ½ × (parallel side a + parallel side b) × height
Parallelogram = base × perpendicular height
Ellipse = π × semi-major axis × semi-minor axis
All results are expressed in square units (m², cm², ft²) matching the input unit.
What Are Some Example Calculations?
Rectangle 5m × 3m = 15 m². Circle with radius 4m = 50.27 m². Triangle with base 6m and height 4m = 12 m².
A rectangular room measures 4.5m by 3.8m. Calculate the floor area for carpet.
Area = 4.5 × 3.8 = 17.1 m².
The room requires 17.1 m² of carpet. Add 10% for waste: order 18.81 m².
A circular pond has a diameter of 6m. Find the surface area.
Radius = 6 / 2 = 3. Area = π × 3² = π × 9 = 28.27 m².
The pond covers 28.27 m² of surface area.
A triangular garden bed has a base of 5m and a height of 3.2m.
Area = ½ × 5 × 3.2 = 8 m².
The garden bed covers 8 m². Divide by the coverage rate per bag to find how much soil to buy.
When Should You Use a Area Calculator?
Use this calculator whenever you need to measure the space inside a flat shape. Common tasks include ordering flooring or carpet, estimating paint coverage for a wall, sizing a garden plot, or calculating land area for a property boundary.
Construction projects require area calculations for material quantities and cost estimates. Students use area formulas in geometry and trigonometry coursework. Select your shape above and enter the dimensions to get an instant answer.
What Do These Terms Mean?
How Do the Options Compare?
| Shape | Formula | Inputs needed |
|---|---|---|
| Rectangle | length × width | Length, width |
| Square | side² | Side length |
| Circle | π × radius² | Radius (or diameter ÷ 2) |
| Triangle | ½ × base × height | Base, perpendicular height |
| Trapezium | ½ × (a + b) × height | Two parallel sides, height |
| Parallelogram | base × height | Base, perpendicular height |
| Ellipse | π × a × b | Semi-major axis, semi-minor axis |
What Are the Best Tips to Know?
- Always use the same unit for all dimensions. Do not mix metres with centimetres in a single calculation.
- For irregular shapes, break them into rectangles and triangles, calculate each area, and add the results.
- Add 10% to your result when ordering materials to account for waste and cutting.
- Measure the perpendicular height for triangles and trapeziums — not a slanted side.
- Convert the final area between units by multiplying: 1 m² = 10,000 cm². 1 m² = 10.764 ft².
What Mistakes Should You Avoid?
- Using the diameter instead of the radius in the circle formula. Divide the diameter by 2 first.
- Forgetting to halve the result for triangles. The formula includes ½ × base × height.
- Mixing units within a single calculation, producing a meaningless result.
- Using a slanted side length instead of the perpendicular height in triangle and trapezium formulas.
- Confusing area (square units) with perimeter (linear units) when ordering materials.
Frequently Asked Questions
What is the difference between area and perimeter?
Area measures the space inside a shape (in square units like m²), while perimeter measures the total length around the outside of a shape (in linear units like m).
How do I calculate the area of an irregular shape?
Break the irregular shape into simpler shapes (rectangles, triangles), calculate each area separately, and add them together.
What units should I use for area?
Area is measured in square units. If your dimensions are in metres, the area is in square metres (m²). If in feet, the area is in square feet (ft²).
How do I convert between square metres and square feet?
Multiply square metres by 10.764 to get square feet. Multiply square feet by 0.0929 to get square metres. For example, 20 m² = 215.28 ft².
How much paint do I need for a wall?
Calculate the wall area (height × width) in m². Subtract window and door areas. Divide the total by the paint coverage rate (typically 10-12 m² per litre). Multiply by the number of coats.
How do I find the area of a room with an alcove?
Split the room into two rectangles. Calculate the area of each rectangle separately and add them together. For an L-shaped room, use the same approach.
What is the area of a semicircle?
Divide the circle area by 2. Formula: ½ × π × radius². A semicircle with radius 3m has an area of ½ × π × 9 = 14.14 m².
How do I calculate acres from square metres?
Divide the area in square metres by 4,046.86. One acre equals 4,046.86 m². For example, 10,000 m² = 2.47 acres.
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