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What is rectangle area?

Rectangle area measures the flat surface a rectangle occupies, expressed in square units (m², cm², ft²…). It's one of the most widely used calculations in architecture, construction, interior design, and school geometry — because most rooms, floors, walls, and plots of land are rectangular.

Rectangle area formula

Area = length × width

For perimeter: Perimeter = 2 × (length + width)

Both dimensions must be in the same unit. If length is in meters and width in centimeters, convert to a common unit first.

Step-by-step example

You want to tile a living room 6.5 m long and 4.2 m wide.

1. Area = 6.5 × 4.2 = 27.3 m²
2. Add 10% for cuts and waste: 27.3 × 1.10 = 30 m² of tiles to buy
3. Perimeter (for baseboard trim): 2 × (6.5 + 4.2) = 21.4 linear meters

Common practical uses

• Flooring and tiling: Calculate how many square meters of hardwood, ceramic, or carpet you need.
• Ceiling and wall paint: One liter of paint covers roughly 8–12 m²; divide the area by that figure to find how many liters to buy.
• Gardens and land: Determine the amount of sod, decorative gravel, or topsoil needed.
• Solar panel installation: Check if available roof area can accommodate the required number of panels.
• Furniture layout: Verify whether a sofa, bed, or table fits in the available floor space.

Häufige Fehler vermeiden

• Mixed units: Mixing meters and centimeters without converting gives results 100 times too large or small.
• Diagonal vs. side: The rectangle's diagonal (√(a²+b²)) is always longer than its sides — don't use it as length or width.
• Forgetting waste allowance: In construction, always add 5–10% to the calculated area for cuts and breakage.
• Rooms with cutouts: Calculate the full rectangle area and subtract the area of any columns or recesses.