Add up rooms and shapes to get total square feet, with an optional waste allowance included.
Quick answer: Square footage is length times width. A room measuring 12 ft by 14 ft is 168 sq ft, and two rooms of that size total 336 sq ft. Add 5–10% waste for cuts on flooring or tile, which turns 336 sq ft into about 353–370 sq ft.
%
Use 5–10% for flooring or siding, 0% for a pure measurement.
Total area
144 sq ft
16.00 sq yd · 13.38 m²
Shapes counted
1
Each row adds to the total
Breakdown
Room 1 (1×)144 sq ft
Total144 sq ft
Add one row per room or shape. For L-shaped rooms, split the shape into two rectangles. Subscribe to the old rule of thumb: measure twice, and write the numbers down before you go shopping.
Core facts
Formula
length × width = sq ft
Units
Feet and inches
Waste
Typically 5–10% for cuts
Also handles
Triangles, circles, L-shapes
What is Square Footage Calculator?
Square footage is the area of a floor, wall or lot measured in feet: length multiplied by width. Measure each room at floor level and write the numbers down before you start adding. Irregular rooms are easier to handle if you split them into rectangles and triangles — a triangle is base times height divided by two, and a circle is 3.14 times the radius squared. Inches convert to feet by dividing by 12, so a 30 in wide counter is 2.5 ft. The calculator keeps a running list of rooms and shapes, counts how many of each you have, and shows both the raw total and the total with your waste allowance added, which is the number you actually shop with.
Common uses for Square Footage Calculator
Add up the square footage of several rooms before ordering flooring
Work out an irregular room by splitting it into rectangles and triangles
Convert inch measurements from a tape into decimal feet for a quote
Include a waste percentage so you order enough tile or carpet
Check the square footage a listing claims against your own measurement
Why you measure at floor level
A tape run along the baseboard can read several inches short in a room with thick skirting, and a measurement taken near the ceiling misses the flare of a plastered wall. Measure the floor itself, at the widest point of each wall, and measure twice. Older houses are rarely square: a room can be 12 ft across at the front wall and 12 ft 4 in at the back. For flooring, average the two; for a sanity check, note the difference before you order.
Waste percentages that hold up
Five percent is fine for a plain square room with few cuts. Ten percent is the usual figure for a room with doorways, corners and angled walls, and it is what most flooring installers order. Fifteen percent makes sense for diagonal layouts, herringbone patterns or tile with a lot of pattern matching, because every cut across the pattern throws material away. Keep one unopened box: matching a dye lot two years later is often impossible.
Square feet, square yards and squares
Square feet is the default, but the trade you are buying from may use something else. Carpet is often priced by the square yard, which is 9 sq ft, so divide your total by nine. Roofing and siding contractors price by the square, which is 100 sq ft. Paint is priced by the gallon with a coverage figure per gallon. Converting early avoids a decimal error later.
Frequently Asked Questions
How do I calculate square footage of an irregular room?
Split it into shapes you can measure: rectangles for the main area, triangles for angled corners and circles for round bays. A triangle is base times height divided by two; a circle is 3.14 times the radius squared. Add the pieces together for the total, and enter each shape as its own row.
How much waste should I add?
Five percent is enough for a simple square layout, ten percent is typical for a room with several corners or an angled pattern, and fifteen percent is sensible for diagonal tile or a herringbone floor. Waste covers offcuts, breakage and a few spare pieces for later repairs.
Do I convert inches to feet before multiplying?
Yes. There are 12 inches in a foot, so divide inches by 12 to get decimal feet — 6 in becomes 0.5 ft. Multiply the two decimal-foot figures to get square feet. A room 10 ft by 12 ft 6 in is 10 times 12.5, or 125 sq ft.
Should closets and stair openings be counted?
Include anything that receives the same finish: a closet with the same carpet counts, a stairwell opening in an upstairs floor does not. For flooring, measure the floor area you will actually cover. For heating or cooling load, use the conditioned floor area instead.