Square Footage Calculator
Measure area for flooring, paint and landscaping: rectangles, circles, L-shapes and more.
Measure the space
This calculates area in square feet for rectangles, circles, triangles and irregular shapes.
It converts between units and adds a waste allowance for flooring and tiling projects.
How to measure square footage
Square footage is area: length times width for a rectangle. A 12 by 14 ft room is 168 sq ft.
The real work is irregular rooms. Break the space into rectangles, calculate each, and add them up. A 12 × 14 room with a 6 × 8 alcove is 168 + 48 = 216 sq ft. Every awkward shape reduces to this.
The step people skip is waste allowance. Flooring and tile need extra for cuts, mistakes and future repairs: 10% for a simple rectangular room, 15% for diagonal layouts or complex shapes. Ordering exactly 216 sq ft for a 216 sq ft room reliably means a second trip.
Decompose, add, then add waste. At 20 sq ft per box that is 12 boxes, since you cannot order a fraction of one.
What to enter
- Length and width
- In feet, or in feet and inches. Convert inches to a decimal by dividing by 12: 6 in is 0.5 ft.
- Shape
- Rectangle, circle, triangle, or several rectangles combined for an irregular space.
- Waste percentage
- 10% for straight layouts in simple rooms; 15% for diagonal or herringbone patterns and complex shapes.
- Coverage per unit
- Square feet per box or per gallon, for converting area into what you actually buy.
Area formulas and conversions
- Rectangle
- length × width.
- Triangle
- ½ × base × height.
- Circle
- π × radius². Remember it is the radius, not the diameter.
- 1 square yard
- 9 square feet. Carpet is often priced this way.
- 1 square metre
- About 10.764 square feet.
What this assumes
Area calculations assume a flat surface. Sloped ceilings and stairs need separate treatment.
Waste allowances are typical rather than guaranteed. Very complex layouts, patterned material and large tiles all push it higher.
How to calculate square footage
Decompose the space, calculate each piece, add them, then add waste.
- irregular shapes
- Sum the areas of the rectangles you divide them into
- waste
- 0.10 for simple rooms, 0.15 for complex or diagonal layouts
Sketch the room and divide it into rectangles. Almost every domestic space reduces to two or three rectangles. Mark each one's dimensions on the sketch.
Measure each section. Convert inches to decimals: 12 ft 6 in is 12.5 ft. Measure at floor level, since walls are rarely perfectly parallel.
Multiply and add. (12 × 14) + (6 × 8) = 168 + 48 = 216 sq ft.
Add waste, then round up to whole units. 216 × 1.10 = 238 sq ft. At 20 sq ft per box that is 11.9 boxes, so order 12.
See a worked example: from measurements to a shopping list
- Main room
- 12 × 14 ft
- Alcove
- 6 × 8 ft
- Flooring
- 20 sq ft per box
Main: 12 × 14 = 168 sq ft. Alcove: 6 × 8 = 48 sq ft. Total 216 sq ft.
With 10% waste: 216 × 1.10 = 238 sq ft.
238 ÷ 20 = 11.9, so 12 boxes.
Ordering exactly 216 sq ft would give 10.8 boxes, and 11 boxes leaves 4 sq ft of margin across the whole job. That is not enough for cuts.
216 sq ft, so order 12 boxes
Frequently asked questions
Break it into rectangles, calculate each, and add them together. An L-shaped room is two rectangles; most awkward spaces are three or fewer.
For genuinely curved walls, approximate with a series of rectangles or use the circle or triangle formula for that section.
10% for a straight layout in a simple rectangular room. 15% for diagonal or herringbone patterns, or rooms with many corners and cuts.
Order the whole job at once so it comes from the same production batch. Tile and flooring colours vary noticeably between batches, and a late top-up order often does not match.
Usually not, and it is safer not to. Flooring often runs under appliances, and future layout changes are easier if it does.
For very large permanent built-ins you can subtract them, but the waste allowance largely covers the difference either way.
Divide by 9 for square yards, since a square yard is 3 ft × 3 ft. So 216 sq ft is 24 square yards.
Divide by 10.764 for square metres. 216 sq ft is about 20.1 m².
Convert to decimal feet by dividing by 12. 6 in is 0.5 ft, 3 in is 0.25 ft, and 12 ft 8 in is 12.667 ft.
Multiplying feet-and-inches directly is the most common measurement error in these calculations. Convert first, then multiply.
Square feet measure area, which is what you need for flooring, tile and paint. Linear feet measure length along a line, which is what you need for skirting, trim and worktop edging.
They are not interchangeable, and quoting one when a supplier expects the other is a common and expensive mix-up.
Problems people actually run into
Ordering the exact area
216 sq ft of flooring for a 216 sq ft room leaves nothing for cuts, breakages or an offcut kept for future repairs.
Add 10-15%, then round up to whole boxes. Returning an unopened box is far easier than matching a dye lot months later.
Measuring feet and inches without converting
12 ft 6 in × 14 ft 3 in is not 12.6 × 14.3. It is 12.5 × 14.25, which is 178.1 sq ft rather than 180.2.
Divide inches by 12 first. It is a small difference on one room and it compounds across a whole house.
Results are estimates for general information only and are not professional financial, medical, or legal advice. Read our full disclaimer.
Last updated: September 4, 2026