What is the area of a rectangle?
The area of a rectangle tells you how much flat space is inside its boundaries. If you imagine laying floor tiles, painting a wall, or covering a field with sod, area is the measurement you need.
Because you multiply two linear dimensions, the answer is in square units: square centimeters (cm²), square meters (m²), square feet (ft²), and so on.
How to use this area of a rectangle calculator
- Enter the rectangle’s length.
- Enter the rectangle’s width.
- Select a unit if you want the result labeled.
- Click Calculate Area to see the result instantly.
This tool handles whole numbers and decimals, so it works for school math problems, construction planning, home improvement, and everyday measurements.
Example calculations
Example 1: Small room
Length = 4 m, Width = 3 m
Area = 4 × 3 = 12 m²
Example 2: Desktop surface
Length = 120 cm, Width = 60 cm
Area = 120 × 60 = 7,200 cm²
Example 3: Garden plot
Length = 18.5 ft, Width = 11.2 ft
Area = 18.5 × 11.2 = 207.2 ft²
Common mistakes to avoid
- Mixing units: Convert both measurements to the same unit before calculating.
- Using perimeter formula by accident: Area is length × width, not 2(length + width).
- Forgetting squared units: Write results as cm², m², ft², etc.
- Negative values: Real lengths and widths must be positive numbers.
Where rectangle area is used in real life
- Estimating flooring, tile, carpet, or laminate needs.
- Calculating paint coverage for rectangular walls.
- Planning furniture layout in rooms.
- Determining land and garden bed sizes.
- Creating accurate project estimates for materials.
FAQ
Can I use decimals?
Yes. Decimal values are fully supported.
What if my measurements are in different units?
Convert one value so both are in the same unit first. For example, change inches to feet or centimeters to meters before multiplying.
Is this calculator for squares too?
Yes. A square is a rectangle with equal sides, so the same formula works: Area = side × side.