Rooms and floors
Measure finished wall to finished wall at floor level. Include closets only when their floors receive the same material. Use an L-shape or separate rows for alcoves and offsets.
Square Footage Calculator
Multiply length by width in feet for a rectangle, or enter measurements below for other shapes, feet-and-inches dimensions, openings, and multiple areas.
Project areas
Use one row per room, wall, zone, or shape. Each dimension can have a different unit.
Applied only to the material order area, not the measured area.
Project estimate (optional)
Enter an area price, package details, or both. Package totals use the material order area after waste.
Results
Unadjusted square footage
0 ft²
Measured area after deductions and quantities, before waste.
Material order area after waste
0 ft²
0 × 1.00 = 0 ft² to order
Enter measurements and calculate to see totals.
Waste added0 ft²
Base square meters0 m²
Base square yards0 yd²
Calculation details
- Add measurements to see conversion and formula steps.
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Square footage formulas
Dimensions are converted to feet before the shape formula is applied. In the formulas below, L is length, W is width, s is side, h is perpendicular height, r is radius, and “outer” and “inner” describe the full and removed shapes.
| Shape | Formula | Short example |
|---|---|---|
| Square | A = s² | 8 ft × 8 ft = 64 ft² |
| Rectangle | A = L × W | 12 ft × 10 ft = 120 ft² |
| Triangle | A = base × h ÷ 2 | 10 ft × 6 ft ÷ 2 = 30 ft² |
| Circle | A = πr² | 10 ft diameter: π × 5² = 78.54 ft² |
| Trapezoid | A = (base₁ + base₂) × h ÷ 2 | (8 ft + 12 ft) × 5 ft ÷ 2 = 50 ft² |
| L-shape | A = outer L × outer W − cutout L × cutout W | 12 × 10 − 4 × 3 = 108 ft² |
| Rectangular border | A = outer area − inner area | 10 × 8 − 8 × 6 = 32 ft² |
| Circle border / ring | A = π(outer r² − inner r²) | 10 ft and 6 ft diameters: π(5² − 3²) = 50.27 ft² |
| Area subtraction | net = shape area − Σ(opening area × quantity) | 120 − (3 × 4 × 2) = 96 ft² |
Area conversions
| Square inches | 1 ft² = 144 in² |
|---|---|
| Square yards | 1 yd² = 9 ft² |
| Square meters | 1 m² = 10.7639 ft² |
| Acres | 1 acre = 43,560 ft² |
Feet and linear feet measure one-dimensional length. Square feet measure two-dimensional area. Board feet measure lumber volume (nominally 12 × 12 × 1 inches), while cubic feet measure three-dimensional volume. Do not substitute one for another.
What square footage should you measure?
Walls
Measure each wall's width and height, multiply by quantity for identical walls, and deduct doors or windows when the product instructions call for net coverage. Paint estimates may intentionally keep small openings as allowance.
Whole houses
A sum of interior room floors is useful for a renovation takeoff, but it is not automatically official gross living area. Exterior measurements, level classification, ceiling height, stairs, finished condition, and local reporting rules may change the result.
Outdoor areas
Measure the plan-view footprint for patios, turf, pavers, sod, or mulch. Split curves and irregular boundaries into measurable shapes. Flat area alone is insufficient for slopes, excavation volume, drainage design, or structural work.
Material ordering
Start with measured project area, subtract true exclusions, multiply by waste, then divide by package coverage and round up. Follow the manufacturer's layout, overlap, pattern-repeat, and batch guidance.
Project area versus real-estate living area
This calculator measures project surfaces from the dimensions you enter. It does not certify gross living area (GLA). In the United States, ANSI Z765-2021, Square Footage—Method for Calculating, provides procedures for detached and attached single-family houses and distinguishes above-grade and below-grade reporting; it does not cover apartment buildings or room-dimension takeoffs. Use a qualified local appraiser or measurement professional for a listing, appraisal, tax, lending, or legal purpose.
Measuring complex areas
For an L-shaped area, measure the full outside rectangle (outer length × outer width) and the missing corner (cutout length × cutout width), then subtract. For a wall, measure total width × height and deduct each opening only when net surface area is needed.
The interactive diagram in each calculator row changes with the selected shape and repeats the field labels in text.
Worked square footage examples
12 × 16 ft room
Measurements: 12 ft by 16 ft.
Formula: 12 × 16 = 192.
Answer: 192 ft² before waste.
Feet-and-inches room
Measurements: 10 ft 6 in by 12 ft 3 in.
Conversion: 10.5 ft × 12.25 ft.
Answer: 128.625 ft² (128.63 ft² rounded).
L-shaped room
Measurements: 12 × 10 ft outer area minus a 4 × 3 ft corner.
Formula: 120 − 12.
Answer: 108 ft². This is equivalent to adding two non-overlapping rectangles.
Wall minus a window
Measurements: 15 × 8 ft wall; one 4 × 3 ft window.
Formula: 120 − 12.
Answer: 108 ft² of net wall.
Flooring with waste and boxes
Area: 192 ft²; waste: 10%.
Order area: 192 × 1.10 = 211.2 ft². At 20 ft² per box: 211.2 ÷ 20 = 10.56 boxes.
Answer: buy 11 boxes, covering 220 ft² with 8.8 ft² surplus.
Square footage FAQs
How many square feet are in a 12 × 12 room?
A 12 ft by 12 ft room is 144 square feet because 12 × 12 = 144. This is the unadjusted floor area before waste.
How do I calculate an L-shaped room?
Measure the outer rectangle and subtract the missing corner, or split the room into two non-overlapping rectangles and add them. For example, 12 × 10 minus 4 × 3 equals 108 square feet.
How do I enter feet and inches?
Choose feet + inches beside a dimension, then enter its whole feet and remaining inches. Each dimension has its own unit, so feet-and-inches and metric or decimal feet can be mixed in one row.
Do closets and stairs count in square footage?
For a material project, include only surfaces being covered. Official gross living area follows a measurement standard and local rules; closets and stair openings can be treated differently from a simple sum of room floors.
How do I subtract doors and windows?
Open Deductions or openings in an area row, add each opening's width, height, and quantity, and the calculator subtracts their extended area from that row.
What waste percentage should I use?
Use the product manufacturer's allowance when available. As a planning range, 5% may suit simple layouts, 10% many flooring or tile layouts, and 15% complex, diagonal, or heavily cut patterns.
How do I calculate material cost or boxes?
Open Project estimate, enter a price per square foot or square meter, or enter package coverage and package price. The calculator applies waste, rounds packages up, and reports purchased coverage, surplus, and total cost.
Methodology, review, and limitations
- Responsible organization
- Starlight Tools (Starlight Robotics)
- Last reviewed
- 16 July 2026
- Method
- Convert each linear dimension to feet, apply the selected geometry formula, subtract openings, multiply by quantity, sum rows, then apply waste and whole-package rounding.
- Constants
- 1 ft = 0.3048 m exactly; 1 m² ≈ 10.7639104167 ft²; 1 yd² = 9 ft²; π uses the browser's full-precision
Math.PIvalue. - References
- Home Innovation Research Labs: ANSI Z765-2021 square footage method FAQ; NIST unit-conversion guidance.
Accuracy and limitations: results are mathematical estimates based on user-entered dimensions. Field measurements, product coverage, installation losses, rounding, and local measurement rules can differ. This tool does not provide an appraisal, survey, structural calculation, code determination, or professional material takeoff.