Rooms · walls · outdoor spaces
Square Footage Calculator
Measure a room, wall, patio, or garden area. Combine simple shapes, subtract excluded sections, and see your net area in square feet, square meters, and square yards.
Worked example
- Included rectangle
- 180 sq ft
- Excluded corner
- 12 sq ft
- With optional 10% allowance
- 184.8 sq ft
Example only. No measurements or material allowance are prefilled from this example.
Your result
Know the area before you shop
Enter your dimensions to see net square footage, metric conversions, and a section-by-section breakdown here.
Suggest an improvement
Before you measure
Choose the surface you actually need to cover.
For floors, patios, and garden areas, measure length and width. For a wall, measure width and height. Trace irregular spaces as simple shapes without counting an overlap twice.
Rectangle or square
Area = length × width. A square uses the same measurement for both.
Triangle
Area = base × perpendicular height ÷ 2. The sloping edge is not the height.
Circle
Area = π × (diameter ÷ 2)². Measure the diameter across the center.
Net area and material allowance
Net area = included area − excluded area. Planning area = net area × (1 + allowance ÷ 100).
An L-shaped room
Start with a 12 × 15 ft rectangle, then subtract a missing 3 × 4 ft corner: 180 − 12 = 168 sq ft. With a chosen 10% material allowance, plan for 184.8 sq ft before rounding to whole packages.
FAQ
Square footage questions
How do I calculate square footage of a room?
For a rectangular room, multiply inside length by inside width after converting both measurements to feet. A 12 ft by 15 ft room is 180 sq ft. Add non-overlapping sections for an irregular room.
How do I enter feet and inches?
Enter 12 ft 6 in as Feet: 12 and Inches: 6. Decimal feet also work: 12.5 ft with Inches: 0 is the same length. For 6 inches only, leave Feet blank or enter 0 and enter Inches: 6.
How do I measure an L-shaped room?
Split it into two rectangles that do not overlap and add both. Alternatively, include the enclosing rectangle and subtract the missing corner. Do not use both methods at once.
What should I subtract?
Subtract only areas inside your included sections that do not need coverage. For a wall, these might be doors or windows; for a floor, a permanent obstruction may qualify depending on your installation plan. Never subtract the same space twice.
How do I calculate a triangle or circle?
For a triangle, multiply the base by the height measured perpendicular to the base, then divide by 2. For a circle, enter the diameter through its center; area is π × (diameter ÷ 2)².
Should I add waste to square footage?
Measured square footage does not include waste. The optional allowance starts at 0% and adds extra material after exclusions. Choose it using your product and layout instructions. Do not apply the same allowance twice when using a material calculator.
Can I use this for paint or a property listing?
For paint, measure each wall’s width and height, not the room’s floor dimensions. Use the Paint Calculator for coats and product coverage. This tool calculates geometric area; it does not determine finished living area for a real-estate listing or appraisal.
How are square feet converted to square meters and square yards?
Square meters = square feet × 0.09290304. Square yards = square feet ÷ 9. Input units can differ between sections, and switching a section’s units converts its existing measurements.
References
Measuring guidance and unit conversions
Home Depot measuring guide
Measure the surface, divide irregular spaces into sections, and account for material waste separately.
View measuring guide ↗NIST unit conversion reference
Conversions use the international foot: 1 ft = 0.3048 m exactly.
View conversion reference ↗