What Is Square Footage?
Square footage is the area of a flat space measured in square feet: how many 1-foot by 1-foot squares would cover it. It's how flooring, carpet, tile, paint, sod and home sizes are measured and priced. Countries that use the metric system measure the same thing in square meters.
- Square feet (sq ft or ft²): the usual unit for rooms and homes in the US.
- Square yards (sq yd): often used for carpet and concrete. 1 square yard is 9 square feet.
- Square meters (m²): the metric unit. 1 square meter is about 10.76 square feet.
- Acres: for land. 1 acre is 43,560 square feet.
How to Calculate Square Footage
For a rectangle, such as most rooms, multiply the length by the width, both in feet:
Other shapes use these formulas:
- Triangle: base × height ÷ 2, where the height is measured straight up from the base.
- Circle: π × (diameter ÷ 2)², with π about 3.1416. A circle 10 feet across is 78.54 sq ft.
- Trapezoid (two parallel sides of different lengths): (side A + side B) ÷ 2 × height.
- Circle border (a ring, such as a path round a tree): the outer circle less the inner one.
- Rectangle border (a frame, such as a path round a lawn): the outer rectangle less the inside one, where the inside is the length and width less two border widths.
For an odd-shaped space, split it into these simple shapes, work out each one, and add them up. Take away anything that won't be covered, such as a fireplace hearth or a kitchen island. Measure in feet and inches? Turn inches into feet by dividing by 12: 12 feet 6 inches is 12.5 feet.
Example
An L-shaped room: a main part 12 feet by 15 feet, plus a nook 6 feet by 8 feet:
- Main part: 12 × 15 = 180 sq ft
- Nook: 6 × 8 = 48 sq ft
- Total: 180 + 48 = 228 sq ft, which is 21.18 m² or 25.33 sq yd.
- Flooring with 10% extra for cuts: 228 × 1.10 = 250.8 sq ft. At $3.50 a square foot, that's $877.80.
How to Use the Square Footage Calculator
"My living room is 12 by 15 feet with a 6 by 8 foot nook. How much flooring do I need, and what will it cost at $3.50 a square foot?" This calculator answers that.
Let's enter the numbers for this example in each box. They are already filled in when the calculator opens, so you can follow along and then change any box to match your own space.
- Measure In: Choose Feet. You can also choose inches, yards, meters or centimeters; every length below uses it. In feet you can type feet and inches, such as 12' 6".
- Extra for Waste: Enter 10, the percent extra to buy for cuts and mistakes. It can be from 0 to 100.
- Price (Optional): Enter 3.50, the material's price. Leave it at 0 to see the area only.
- Price Per: Choose Square foot. Choose square yard or square meter if that's how the price is given.
- Area 1: Choose Rectangle and Add, then enter a length of 12 and a width of 15.
- Area 2: Choose Rectangle and Add, then enter 6 and 8. Click + Add Area for more parts, up to 20, choose Take away for parts that won't be covered, or × to remove one. Each shape asks for its own sizes, such as a diameter for a circle.
Calculate and Reset
Click Calculate to see your results. If a box has a problem, such as letters, an empty size, or a border too wide for its shape, a message pops up under that box instead. With the default numbers you get:
- Your Results: the total area (228 sq ft), the same in square meters and square yards, the amount to buy with extra for waste, and the cost.
- Total area: the headline, 228 sq ft. When you measure in meters or centimeters, it's in square meters instead.
- Square Meters and Square Yards: 21.18 and 25.33.
- To Buy, With 10% Extra: 250.8 sq ft.
- Material Cost: $877.80. With no price entered, this shows the area in acres instead.
- Areas: each part's shape, size and area, with the total underneath.
- Share Results: a link that opens this calculator with your areas filled in. Copy it, or share it on Facebook or X.
Click Reset to put every box back to its default and show the default results again. Measure twice before buying, and check how your material is sold: tile and flooring often come in boxes that cover a set area, so round up to whole boxes.