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Area Calculator

One tool, 9 shapes: square, rectangle, triangle, circle, trapezoid, parallelogram, ellipse, rhombus, and regular polygon. Get area and perimeter instantly with the formula shown.

9
Shapes in One
Instant
Live Results
100%
Free & Accurate

Why Use This Area Calculator?

  • ✓ Covers every common 2D shape in one place.
  • ✓ Shows the exact formula used and, where applicable, the perimeter too.
  • ✓ Includes a labeled diagram for every shape to avoid measurement mix-ups.

On This Page

Area Calculator Formula Reference Table Worked Examples Best Practices FAQs Related Calculators

Area Calculator

Square — Area & Perimeter

Rectangle — Area & Perimeter

Triangle — Area (Base & Height)

Circle — Area & Circumference

Trapezoid — Area

Parallelogram — Area & Perimeter

Ellipse — Area & Approx. Perimeter

Rhombus — Area & Perimeter

Regular Polygon — Area & Perimeter

Shape Diagram

Results

Formula Used
Area = s²
Area
25
Perimeter
20

A square with side 5 has an area of 25 and a perimeter of 20.

Area & Perimeter Formula Reference

Shape Area Formula Perimeter / Circumference
Squares²4s
Rectanglel × w2(l + w)
Triangle(b × h) ÷ 2Sum of all three sides
Circleπ × r²2 × π × r
Trapezoid½ × (a + b) × hSum of all four sides
Parallelogramb × h2(b + side)
Ellipseπ × a × bπ[3(a+b) − √((3a+b)(a+3b))]
Rhombus½ × d₁ × d₂4 × √((d₁/2)² + (d₂/2)²)
Regular Polygon(n × s²) ÷ (4 × tan(π/n))n × s

Worked Examples

Example 1 — Rectangle, length 8 and width 5

Area = 8 × 5 = 40. Perimeter = 2(8+5) = 26.

Example 2 — Triangle, base 6 and height 4

Area = (6 × 4) ÷ 2 = 12.

Example 3 — Circle, radius 7

Area = π × 7² ≈ 153.94. Circumference = 2π × 7 ≈ 43.98.

Example 4 — Regular hexagon, side 5

Area = (6 × 5²) ÷ (4 × tan(30°)) ≈ 64.95. Perimeter = 6 × 5 = 30.

Where Area Calculations Are Used

🏗 Construction & Flooring

Estimate materials for flooring, tiling, painting, and roofing projects.

🌱 Landscaping & Gardening

Plan lawn size, garden beds, mulch coverage, and fencing needs.

🎓 Geometry & School

Solve homework problems and understand shape properties visually.

🏠 Real Estate

Calculate room, floor plan, or property area for listings and renovations.

🎨 Design & Art

Determine canvas, fabric, or material coverage for creative projects.

⚙ Engineering

Calculate cross-sectional areas for structural and mechanical design.

Best Practices & Common Mistakes

✅ Best Practices

  • Always use the same unit for every measurement before calculating.
  • Use perpendicular height, not the slanted side, for triangles and parallelograms.
  • Double-check which formula applies to your exact shape.
  • Round only your final answer, not intermediate calculations.
  • Use the diagram to confirm you are measuring the correct dimension.

❌ Common Mistakes

  • Using the slant height instead of the perpendicular height.
  • Mixing up radius and diameter for circles.
  • Forgetting to divide by 2 for triangle area.
  • Confusing area (square units) with perimeter (linear units).
  • Using irregular polygon formulas for non-regular shapes.

Frequently Asked Questions

Multiply the length by the width: Area = length × width.
Multiply pi by the radius squared: Area = π × r².
Multiply the base by the perpendicular height and divide by two: Area = (base × height) ÷ 2.
Area measures the space inside a two-dimensional shape (in square units), while perimeter measures the total distance around its outer edge (in linear units).
Break the irregular shape into simpler shapes (rectangles, triangles, circles), calculate each area individually, and add them together.
Unlike a circle, an ellipse has no simple exact formula for its perimeter. Ramanujan's approximation used here is extremely accurate for nearly all practical purposes.
Yes. Every shape uses its standard geometric formula, calculated with full decimal precision in your browser.

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