Square Footage Calculator
Area
168 square feet
A 12 by 14 foot area. Take this figure to whichever material you are buying.
- Square yards
- 18.67
- Square inches
- 24,192
- Perimeter
- 52 feet
This measures one rectangle. An L-shaped room is two: split it at the corner, run each through and add them — taking the longest length by the widest width is how people overestimate a room by a third. The perimeter is the full loop and does not subtract doorways.
How this is calculated
Square footage is length times width, and the only thing that reliably goes wrong is the units. Measure both sides in the same unit before you multiply, because a room measured twelve feet by a hundred and sixty-eight inches is the same room but the arithmetic will not agree unless you convert first. This calculator works internally in inches and converts once, at the end, so a decimal like twelve and a half feet behaves exactly as you would expect rather than being quietly truncated. The three figures underneath the headline exist because different trades quote in different units: carpet and turf are usually sold by the square yard, tile and sheet materials by the square foot, and anything you are cutting to fit is easier to think about in inches. The perimeter is there because it is the number you need for edging, skirting, trim and border stone, and it is the one people most often go back and measure a second time.
Worked example
Twelve times fourteen is 168 square feet. Divided by nine that is 18.67 square yards, which is what a carpet supplier will quote in. The perimeter is twice the sum of the sides, so 52 feet of skirting board — and that is before you subtract the doorway.
Inputs: A room 12 feet by 14 feet
Result: 168 square feet, or 18.67 square yards, with a 52 foot perimeter
What this assumes
- The area is a rectangle. For an L-shaped room, split it into rectangles, work out each one and add them together.
- Measurements are in feet. Enter part-feet as decimals — nine inches is 0.75, not 0.9.
- The perimeter is the full loop. It does not subtract doorways or openings.
Questions
- How do I measure an L-shaped room?
- Split it into two rectangles, run each through the calculator, and add the results. Do not measure the longest length and the widest width and multiply those, which is the most common way people overestimate a room — by a third if the missing corner is a quarter of the rectangle you measured, and by more the deeper it cuts in.
- Why does my supplier quote square yards?
- Carpet, turf and some paving are traditionally sold by the square yard, which is nine square feet. The conversion is in the results, so you can measure in feet and buy in yards without doing it in your head at the counter.
- Should I add waste to this number?
- Not here. This is the area you have. Waste belongs with the material, because how much you need depends on what you are laying — tile wants ten to fifteen percent for cuts, concrete about ten for spillage, paint none at all. Each material calculator adds its own.
- What will it cost to cover this area?
- Type a price per square foot — how flooring, turf, decking and tile are usually quoted — and the result card multiplies it by the area. This page deliberately adds no waste allowance to that figure, because it measures an area rather than recommending a purchase, so the cost is for exactly the area you measured. Add your own allowance if you are buying material to cover it.