Square Footage Calculator
Calculate square footage from a rectangular length and width, optionally totaled across multiple identical sections.
Calculator Inputs
Length must be greater than 0. In feet + inches mode, enter the whole feet here.
Width must be greater than 0. In feet + inches mode, enter the whole feet here.
The unit for every length on this page. In feet + inches mode, added areas and cut-outs are entered in decimal feet (6 in = 0.5).
Number of identical sections to total, a whole number of 1 or more.
| Length | Width | Remove row |
|---|---|---|
| No rows yet. Use "Add row" to add one. | ||
Optional. Each row is a rectangle added to the total, in the selected unit. Up to 20 rows.
| Length | Width | Remove row |
|---|---|---|
| No rows yet. Use "Add row" to add one. | ||
Optional. Each row is a rectangle removed from the total, in the selected unit. Up to 20 rows.
Optional extra for cuts and offcuts when buying flooring or tile (often 5-15%). Leave at 0 for the measured area only.
- Area (Square Feet)
- 120.00
- Area (Square Meters)
- 11.15
- Area (Square Yards)
- 13.33
- Area to Buy incl. Waste (Square Feet)
- 120.00
About these results
CalcSpectrum calculators produce automated estimates using established formulas and the specific values you enter. Because real-world outcomes depend on input accuracy, mathematical assumptions, and rounding conventions, please verify critical figures with an appropriately qualified financial, tax, medical, legal, or other professional, as relevant.
How It's Calculated
Formula
Square Footage calculates area FROM measured dimensions — this is different from Area Converter, which converts an existing area quantity between units. Every length is first converted to feet (1 inch = 1/12 foot; 1 meter = 1/0.3048 feet; 1 centimeter = 1/30.48 feet; in feet + inches mode, 12 ft 6 in = 12.5 ft). The main rectangle's area is multiplied by the quantity of identical sections, any added rectangles (other rooms, or the second leg of an L-shaped room) are added, and any cut-outs (a kitchen island, a stairwell) are subtracted. Square meters (x 0.09290304, exact) and square yards (÷ 9) are derived from the square-foot total. The optional waste allowance only affects the "area to buy" line, never the measured total. Added areas and cut-outs are rectangles; split any irregular room into rectangles to measure it. A blank table row is ignored; a row with only one dimension filled in is flagged so a missed measurement isn't silently counted as zero.
Worked Examples
10 ft x 12 ft room
- Length and width are already in feet: 10 ft, 12 ft.
- Area: 10 x 12 = 120 sq ft.
- Square meters: 120 x 0.09290304 = 11.148365 sq m.
10 ft x 12 ft room, 3 identical sections
- Area of one section: 10 x 12 = 120 sq ft.
- Total across 3 sections: 120 x 3 = 360 sq ft.
L-shaped room measured as 12 ft 6 in x 10 ft plus a 6 ft x 4 ft leg
- Select Feet + inches. Main rectangle: 12 ft 6 in = 12.5 ft, so 12.5 x 10 = 125 sq ft.
- Add the leg as an added area: 6 x 4 = 24 sq ft.
- Total: 125 + 24 = 149 sq ft, which is 16.56 sq yd (149 ÷ 9).
Kitchen floor minus an island, with 10% waste for tile
- Main rectangle: 14 x 12 = 168 sq ft.
- Cut-out for a 6 ft x 3 ft island: 6 x 3 = 18 sq ft. Measured area: 168 - 18 = 150 sq ft.
- Area to buy with a 10% waste allowance: 150 x 1.10 = 165 sq ft.
Frequently Asked Questions
How is this different from the Area Converter?
Square Footage calculates area from a length and width you measured. Area Converter instead takes an area value you already have and converts it between units (for example, square meters to acres). Use Square Footage when you have dimensions; use Area Converter when you already have an area figure.
Can I enter measurements in feet and inches?
Yes. Choose Feet + inches and enter the whole feet in Length and Width and the remaining inches in the inches fields (12 ft 6 in is 12 and 6). Added areas and cut-outs in that mode take decimal feet, so 6 inches is 0.5. Every length on the page uses the one selected unit.
How do I measure an L-shaped room or several rooms?
Split the space into rectangles. Enter one rectangle as the main length and width, then add each other rectangle as a row under Added areas. For several rooms of different sizes, add each room as its own row. Use Cut-outs for anything you don't need to cover, such as a kitchen island.
What is the quantity field for?
Quantity totals the area across multiple identical sections of the same length and width, such as several identical rooms. It must be a whole number of 1 or more. Rooms of different sizes go under Added areas instead.
Should I add a waste allowance?
Only when you are buying material that gets cut, such as flooring, tile or turf; installers commonly add about 5-15% depending on the layout and material. The allowance only changes the Area to Buy line; the measured area stays exact.
Why are negative or zero dimensions rejected?
A rectangle's length and width must be positive to have a defined physical area; zero or negative values are not valid measurements. A table row left at 0 by 0 is treated as not filled in and ignored.