Area Calculator
Calculate the area of squares, rectangles, triangles, circles, trapezoids and parallelograms instantly, with diagonals too.
Area
25
Diagonal
7.07
Side × √2
Area Calculator on True Calculator gives you an instant, accurate answer with no sign-up and no app install. Calculate the area of squares, rectangles, triangles, circles, trapezoids and parallelograms instantly, with diagonals too. Every result shows the formula and a worked example so you can verify the calculation yourself, and all values are computed in your own browser — your numbers never leave your device.
Popular uses: area calculator · area of a rectangle · area of a circle
Reviewed by the True Calculator team · Last updated: August 2026
How We Calculate
This calculator uses standard mathematical formulas — the same ones taught in school and used in exams — verified by our team. All calculations are performed instantly in your browser using JavaScript, so no data is sent to any server.
The formulas follow standard mathematical definitions and conventions used in textbooks and by educational boards. Results are rounded transparently and shown with the exact formula on this page.
When to Use This Calculator
Area calculations sit behind most renovation and construction quotes in India, from tiles and marble to turf and paint. A contractor estimating vitrified tiles for a hall, a builder quoting tarpaulin or waterproofing for a terrace, and a landlord measuring a flat for carpet area all multiply length by width, or use the correct shape formula when rooms are cut by staircases, bay windows or triangular corners. The tool's circle mode handles wells, circular planters and overhead-tank bases, while the trapezoid mode fits sloped-site plots common in hill towns. Architects and interior designers use the same figures to compute lighting density and furniture fit. Students preparing for school and competitive exams also verify mensuration sums here, checking formulas such as ½ × base × height for triangles against textbook answers.
How to Use This Calculator
- Step 1: Choose the shape that matches your floor, plot or object — square, rectangle, triangle, circle, trapezoid or parallelogram.
- Step 2: Enter the dimensions shown for that shape, such as side, length and width, or base and height.
- Step 3: Read the area in square units of whatever unit you entered, such as m² or ft².
- Step 4: Note the diagonal or diameter shown alongside when you need it for flooring cuts or site diagonals.
Worked Example
A flat owner in Pune is tiling a living room that is 5 m by 4 m. Entering the rectangle shape with 5 and 4 returns an area of 20 m² — the quantity the tile dealer quotes against, plus a diagonal of about 8.06 m. A circular veranda of radius 7 m gives about 153.94 m², while a trapezoidal kitchen layout with parallel sides of 5 m and 7 m and height 4 m covers 24 m². For a triangular corner balcony with base 6 m and height 4 m, the area is 12 m², exactly half the base-times-height rectangle.
Tips and Common Mistakes
- •Tip 1: Convert all dimensions to the same unit before entering — a 5 m × 400 cm room is 20 m², not 2,000.
- •Tip 2: For irregular plots, split them into rectangles and triangles and add the areas.
- •Tip 3: Add 5–10% wastage when ordering tiles, since cutting around columns and corners eats into coverage.
- ✗Mistake 1: Using side lengths for a triangle when you actually know base and height — the tool expects those two.
- ✗Mistake 2: Forgetting that area answers in square units, so flooring quotes need m² while carpet fitters may quote ft².
Frequently Asked Questions
How is the area of a rectangle calculated?
Multiply the length by the width. A living room that is 5 m by 4 m has an area of 20 m², which is what you would quote when buying tiles or carpet.
Why is the area of a triangle half of base times height?
Any triangle can be seen as half of a rectangle with the same base and height, so the area is ½ × base × height. A triangle with base 6 m and height 4 m covers 12 m².
What is the formula for the area of a circle?
The area is π × radius². A circular garden with radius 7 m has an area of about 153.94 m². If you only know the diameter, halve it first to get the radius.
How do I calculate the area of a trapezoid?
Average the two parallel sides and multiply by the height: ½ × (side A + side B) × height. For sides of 5 m and 7 m with a height of 4 m, the area is ½ × 12 × 4 = 24 m².
What is the difference between area and perimeter?
Area measures the surface enclosed by a shape in square units, while perimeter measures the boundary length. When tiling a floor you need area; when buying baseboard or fencing you need perimeter.
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