Square Footage Calculator
Use this square footage calculator for one room or a whole house: enter one room per line as length x width and the total appears at once, in square feet and square metres. Irregular rooms are split into rectangles, and circles, triangles and trapezoids have their own formulas.
Source: NIST SP 811, Appendix B.8 – square foot = 9.290 304 × 10⁻² m² (exact). Updated: .
How it is calculated
How to calculate square footage
- Rectangle (room, floor, wall): length × width. A 12 ft × 10 ft bedroom is 120 sq ft.
- Triangle: base × height ÷ 2.
- Circle: π × (diameter ÷ 2)². A 10 ft round patio is 78.5 sq ft.
- Trapezoid: (a + c) ÷ 2 × h.
Measurements in feet and inches? Convert inches to decimal feet first: 10 ft 6 in = 10.5 ft (6 ÷ 12). For irregular or L-shaped rooms, split the floor into rectangles and enter each on its own line.
Flooring and tile
For flooring, add a waste allowance – typically 5–10 %, more for diagonal tile patterns – to the total before you buy. Boxes list the square footage they cover: divide your total by that figure and round up.
Square feet and square metres
1 sq ft = 0.0929 m² exactly (0.3048 m × 0.3048 m), and 1 m² = 10.76 sq ft. Switch "Measurements in" to metres if your tape measure is metric; the result is shown in both units.
Counting part of an area
Put a percentage after a line to count only part of it, for example a porch you want to show separately at 50 %. Official square footage for listings and appraisals follows local standards, so use this as a planning estimate.
Related tools: the concrete calculator for slabs, inches to cm for conversions, and the proportion calculator to scale prices per square foot.
Frequently asked questions
How do I calculate square footage?
Multiply length by width in feet. A room 12 ft by 10 ft is 120 sq ft. For several rooms, add the areas.
How do I calculate square footage with feet and inches?
Turn the inches into a decimal of a foot (divide by 12), then multiply. 12 ft 6 in × 10 ft = 12.5 × 10 = 125 sq ft.
How do I measure an irregular room?
Split it into rectangles (and triangles if needed), work out each part and add them up – one line per part in the calculator.
How much flooring do I need?
Take the room’s square footage and add 5–10 % for cuts and waste. 120 sq ft + 10 % = 132 sq ft to buy.
How many square feet are in a square metre?
1 m² is 10.764 sq ft; 1 sq ft is 0.0929 m².
Sources and legal basis
As of:
Related tools
- Concrete CalculatorConcrete calculator for slabs, footings, round post holes and tubes: cubic yards, cubic feet and m³ with waste, plus how many 40, 60 or 80 lb bags you need.
- Inches to cm converterConvert inches to cm and cm to inches: 1 in = 2.54 cm. Includes fractions to 1/16″, feet and inches for height, and TV or monitor width and height.
- Proportion CalculatorSolve direct and inverse proportion problems (rule of three) online: find x from a ↔ b and c, with the unit value and step-by-step working.
- Unit price calculatorCompare 2–4 package sizes by price per ounce, fluid ounce, 100 g, kg or liter. Shows the best deal and how much you save in percent – oz, lb, g, mL, L or count.
- Bar to psi converterConvert bar to psi and back: 1 bar = 14.504 psi. Also pascal, kPa, atm, mmHg and water column – with the working, a chart and a note on psig vs psia.
- Bra size calculator – measure underbust and bustBra size calculator: enter your underbust and bust in inches or cm to get band and cup, converted to US, UK, EU, FR and AU sizes, plus sister sizes. Free.