Square Footage Calculator
Measure a room or lot in feet, and get the area in square feet with conversions to square yards, square meters and acres — plus a cost estimate if you enter a price per square foot for flooring, paint or rent.
Square footage formula
For any rectangle, area is length times width, both measured in feet. For an L-shaped or irregular room, split it into rectangles, compute each one, and add them up — that's how pros measure houses too.
Conversions: a square yard is 3 ft × 3 ft = 9 sq ft (carpet is often quoted per sq yd); an acre is 43,560 sq ft; a square meter is about 10.764 sq ft. Materials are then area × unit price, usually plus 5–10% cut waste for flooring.
Worked examples
Example 1: flooring for a bedroom
A 12 ft × 10 ft bedroom; flooring costs $4.50 per sq ft. Total cost?
- Area of the rectangle.12 × 10 = 120 sq ft
- Multiply by the price.120 × $4.50 = $540
- Real orders add ~10% cut waste.120 × 1.10 = 132 sq ft → $594
120 sq ft of floor, about $540 in material ($594 with 10% waste).
Example 2: an L-shaped room
An L-shaped living room: the main part is 15 × 12 ft, the nook is 6 × 4 ft.
- Split the L into two rectangles and compute each.15 × 12 = 180; 6 × 4 = 24
- Add them.180 + 24 = 204 sq ft
204 sq ft total.
Example 3: lot size in acres
A 150 ft × 120 ft lot — how many acres?
- Area in square feet.150 × 120 = 18,000 sq ft
- Divide by 43,560.18,000 ÷ 43,560 = 0.41 acres
About 0.41 acres — a typical suburban lot.
FAQ
How do I measure a room in inches and get square feet?+
Convert inches to feet first (divide by 12), then multiply. A 148 in × 126 in room is 12.33 ft × 10.5 ft ≈ 129.5 sq ft. Multiplying the inches first gives square inches, which you'd divide by 144.
How many square feet are in a square yard, and why does carpet use yards?+
9 sq ft per sq yd. Carpet rolls historically come in 12-ft widths cut by the yard, so the trade kept square yards; multiply a sq-yd price by 9 to compare with sq-ft prices... divide the sq-ft total by 9 to order.
Is square footage of a house measured the same way?+
Listed house square footage normally counts finished, heated living space measured from exterior walls, excluding garages and unfinished basements. Standards differ by region (ANSI is common in the US), which is why listings and tax records can disagree.
How much extra should I order for flooring waste?+
5–10% for straight-lay planks or tile in a simple room, 10–15% for diagonal patterns, stairs or rooms with many cuts. Tile sold by the box rounds up to full boxes anyway.
What about circles and triangles?+
Circle: π × radius². Triangle: base × height ÷ 2. This anchor page covers rectangles; shape-specific area pages are planned, and for odd shapes you can approximate with rectangles.
Related calculators
- Paint CalculatorWork out how many gallons of paint a room needs: walls from the dimensions, minus doors and windows, times coats, at the real spread rate — steps shown.
- Sq Ft ↔ Acres ConverterConvert square feet to acres and acres to square feet (1 acre = 43,560 sq ft), with the division shown and real-world size comparisons.
- Concrete CalculatorWork out how much concrete you need for a slab: cubic yards, 60 lb and 80 lb bag counts, and waste allowance — with the math shown step by step.