Area Calculator
Pick a shape, enter measurements, and click calculate.
Tip: area is always measured in squared units (for example, m2 or ft2).
What is area?
Area tells you how much surface a 2D shape covers. Think of painting a wall, laying floor tile, or covering a garden bed with mulch. In each case, you need the space inside the boundary of a shape, not just the distance around it.
Perimeter measures the outside edge. Area measures the inside space. That difference matters a lot in school math, construction, design, and everyday planning.
General steps for calculating area
- Step 1: Identify the shape (rectangle, circle, triangle, etc.).
- Step 2: Use the correct formula for that shape.
- Step 3: Make sure all measurements use the same unit.
- Step 4: Substitute values and calculate carefully.
- Step 5: Write the final answer in squared units.
Most common area formulas
1) Rectangle
Formula: A = length × width
Example: if length = 9 m and width = 4 m, then area = 36 m2.
2) Square
Formula: A = side × side = s2
Example: side = 7 cm, so area = 49 cm2.
3) Triangle
Formula: A = 1/2 × base × height
Use the perpendicular height, not a slanted side. If base = 10 and height = 5, area = 25 square units.
4) Circle
Formula: A = πr2
If radius = 3 ft, area = π × 9 ≈ 28.27 ft2.
5) Trapezoid
Formula: A = 1/2 × (a + b) × h
Where a and b are parallel sides and h is height.
6) Parallelogram
Formula: A = base × height
Again, height is perpendicular to the base.
Composite shapes (break them apart)
Some figures are not simple single shapes. A practical method is to split the figure into easy pieces (rectangles, triangles, circles), calculate each area, and then add or subtract as needed.
- Add areas for attached pieces.
- Subtract areas for cut-outs or holes.
- Draw guidelines to make dimensions clearer before computing.
Units and conversions
Always convert lengths first, then calculate area. Because area uses squared units, conversion factors are also squared:
- 1 m = 100 cm, so 1 m2 = 10,000 cm2
- 1 ft = 12 in, so 1 ft2 = 144 in2
- 1 yd = 3 ft, so 1 yd2 = 9 ft2
Common mistakes to avoid
- Using perimeter formulas when asked for area.
- Forgetting to square units in the final answer.
- Using diameter in circle area formula without dividing by 2 for radius.
- Using slanted side instead of perpendicular height for triangles and parallelograms.
- Mixing centimeters and meters without converting.
Real-life uses of area
Learning area is practical, not just academic. You use it to estimate:
- Paint needed for a wall or ceiling
- Tile required for kitchens and bathrooms
- Sod or fertilizer for lawns
- Fabric coverage for upholstery projects
- Solar panel surface planning
Quick reference checklist
- Know your shape.
- Choose the right formula.
- Use consistent units.
- Compute carefully.
- Label answer with square units.
Use the calculator above whenever you need a fast answer, then verify your steps manually to build confidence and accuracy.