Square footage is the language of American property and renovation: rooms are priced by it, flooring is sold by it, and rent is justified by it. This calculator multiplies a rectangle's length by its width — with each dimension allowed in its own unit — and reports the area in square feet, square inches, square yards, square metres, and acres at once.
How It Works
The feature that saves real-world headaches is mixed units: length and width each carry their own unit selector (feet, inches, yards, metres, centimetres), and the engine converts both to feet before multiplying — 1 m = 3.28084 ft, 1 yd = 3 ft, 1 in = 1/12 ft. Measure a room as 5 metres long with a tape that reads 12 feet wide and you can enter exactly that. Outputs convert from the square-foot result: square inches ×144, square yards ÷9, square metres ×0.092903, acres ÷43,560.
Worked Examples
A bedroom, 16 ft × 12 ft: 192 sq ft — also 27,648 sq in, 21.33 sq yd, 17.84 sq m, and 0.0044 acres. The square-yard figure is the one a carpet quote will use; the square-metre figure is what an international flooring supplier wants.
Mixed units, 5 m × 12 ft: 5 m converts to 16.404 ft, so the area is 16.404 × 12 = 196.85 sq ft. Converting first and multiplying second is the only safe order — multiplying raw numbers across units produces a figure in no unit at all.
An L-shaped room: this tool prices one rectangle at a time, so split the L into two rectangles, run each, and add. A 16 × 12 ft main area (192) plus a 10 × 8 ft alcove (80) totals 272 sq ft; add the flooring waste allowance below and the order quantity is about 300 sq ft — roughly 3.50 per sq ft.
Measuring Well and Buying Well
Measure wall to wall at floor level, in two places per dimension — older rooms are rarely perfectly rectangular, and the larger reading is the safer one for material orders. Sketch the space and split anything non-rectangular into rectangles (plus triangles or circles via the Area Calculator for gables and round patios). Then add waste: 10% for straight-lay flooring or carpet, 15–20% for tile in diagonal or herringbone patterns where perimeter cuts multiply. When comparing quotes, insist every bidder prices the same measured area — "price per square foot" games are usually area games underneath.
A Warning About Listing Square Footage
The square footage in a property listing follows conventions that may not match your tape measure. Under the ANSI Z765 standard used for US appraisals, only finished, above-grade space with adequate ceiling height counts toward living area — basements (even finished ones), garages, and low-ceiling attic rooms are reported separately, and exterior wall thickness is included in the measurement. Two honest measurements of the same house can differ by hundreds of square feet purely by convention, which is why price-per-square-foot comparisons only work between properties measured the same way — and why verifying with your own calculation before a purchase is money well spent.
Frequently Asked Questions
How do I measure a room that is not rectangular?
Decompose it. Every floor plan is some combination of rectangles, triangles, and circles: measure and calculate each piece separately (this tool for the rectangles, the Area Calculator for the rest), then add the pieces — subtracting any cut-outs like hearths or stairwells.
How many square feet are in an acre, and why that number?
Exactly 43,560 — a historical artifact: an acre was defined as one chain (66 ft) by one furlong (660 ft), and 66 × 660 = 43,560. The calculator reports acres automatically for large areas like plots and fields.
Should the square footage include closets and hallways?
For material orders, yes — you will floor them, so measure them (as their own small rectangles). For living-area comparisons, conventions differ: ANSI counts hallways and closets within the finished above-grade envelope but excludes unfinished or below-grade space. Decide which question you are answering before you measure.