Free area calculator

Rectangle Area Calculator

Rectangle Area Calculator: Find the area of a rectangular patio, deck, garden bed, or sheet of material. Enter length and width in any

Rectangle Dimensions

Material Waste FactorOPTIONAL

Estimate Material CostOPTIONAL

Calculation Results

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1 ft (12 in) 1 ft 1 ft² = 144 in²

Rectangle Square Footage Calculator: Area Formula and Construction Uses

Rectangles show up everywhere in construction and real estate. Most rooms, lawns, driveways, patios, decks, pools, and foundation slabs are rectangular. You multiply length by width to get area. That one step sits behind almost every home improvement material estimate.

Enter length and width in any unit. The calculator returns area in square feet, square metres, square yards, and acres. Use the waste factor slider to add the overage your material needs.

Length (L)Width (W)Area = L × Wsquare feet

Rectangle Area Formula

The formula is Area = Length × Width. Both measurements must use the same unit before you multiply. If length is in feet and width is in inches, convert one first. Twelve inches equals one foot, so divide inch measurements by 12. The result is in square feet when both inputs are in feet, square metres when both are in metres, and so on.

For partial feet, convert feet and inches to a decimal before multiplying. A room measuring 14 ft 6 in has a decimal length of 14.5 ft. A wall measuring 9 ft 3 in is 9.25 ft. Multiplying decimals gives the correct square footage without rounding errors that build up when you round each dimension first.

Rectangle Applications in Construction

  • Flooring: L × W = floor area; add 10% waste for tile, 10% for hardwood
  • Drywall: (perimeter × ceiling height) / 32 = number of 4'×8' sheets
  • Patio/deck: L × W = area for pavers, composite boards, or concrete
  • Lawn seed/fertiliser: L × W = coverage area for spread rate calculation
  • Paint: (2×L + 2×W) × height = total wall area before subtracting openings
  • Concrete slab: L × W × depth = volume in cubic feet ÷ 27 = cubic yards
  • Roofing: L × W × pitch factor = actual roof area (footprint underestimates slope)
Inner Area(subtract)Border area= Outer − InnerOuter: L₁×W₁ Inner: L₂×W₂

Rectangle Border / Frame Area

A rectangle border is the area between two concentric rectangles. Picture frames, border tile around a room, pool surrounds, and lawn around a building footprint all work this way. The formula is Border Area = (Outer Length × Outer Width) − (Inner Length × Inner Width).

Example: A 20 ft × 30 ft patio surrounds a 12 ft × 22 ft pool. The patio (border) area is (20×30) − (12×22) = 600 − 264 = 336 sq ft. That is the concrete or paver area you need, not the full outer rectangle.

Units and Conversion for Rectangle Area

For measurements in different units: multiply square feet by 0.0929 to get square metres. Multiply square feet by 0.1111 to get square yards. Multiply square feet by 0.0000229568 to get acres. Our calculator handles all conversions at once. When ordering materials priced in square yards (some carpet and artificial turf suppliers), divide your square footage by 9 to get square yards.

Related tools: irregular shape calculator · flooring calculator · concrete calculator · lawn calculator

Rectangle vs. Square: Key Differences in Application

A square is a rectangle where length equals width. For a square room, the area formula is the same (s × s = s²), but material waste patterns differ. Square rooms let you centre tile on all walls at once. Rectangular rooms force a choice: centre on the long wall (cut tiles on the short walls) or centre on the short wall (larger offcuts on the long walls). Square rooms with large-format tile (24"×24" or larger) give the most balanced layout. For rectangular rooms, mark the centreline along the longest axis before laying the first tile so both ends look even.

Square Rooms × s = areaTile centres on all axess = s → balanced layout

How It Works

1

Select Shape

Choose the shape that matches your space.

2

Enter Dimensions

Enter measurements in any unit. Add quantity, waste factor, and material price if you need them.

3

Get Results

See area in ft², in², yd², m², and acres, plus a cost estimate when you enter a price.

Frequently Asked Questions

Multiply length by width. A rectangle 15 ft long and 10 ft wide is 150 square feet. Enter both dimensions and click Calculate for results in all units.
Area = Length × Width. Both measurements should use the same unit. If they do not, the calculator converts them before computing area.
Use a tape measure or laser distance meter. Measure length along the longest wall and width along the shorter wall at floor level. Walls are not always straight, so measure in at least two spots and use the average.
Measure both pairs of opposite walls and average each dimension. If one wall is 12.1 ft and the opposite is 11.9 ft, use 12 ft. That gives a fairer estimate when the room is not perfectly rectangular.
This calculator shows square feet, square inches, square yards, square meters, and acres automatically. After you click Calculate, all five appear with no manual conversion.
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