How do I calculate the square footage of a room?

Measure the length and width of the room in feet, then multiply them together: square footage = length × width. For a 12 ft by 10 ft room, that's 12 × 10 = 120 square feet. If the room isn't a simple rectangle, split it into rectangular sections, calculate each separately, and add the totals.

How many square feet is a 20x20 room?

A 20 ft by 20 ft room is 400 square feet (20 × 20 = 400). This is a common size for a two-car garage or a large living room.

How do I convert square feet to square metres?

Multiply your square footage by 0.0929 to get square metres (or divide by 10.764). For example, 120 sq ft × 0.0929 ≈ 11.15 m². This calculator does the conversion automatically if you set the output unit to square metres.

Does square footage include closets and hallways?

For a DIY flooring or paint measurement, yes — measure everything you'll actually need to cover. For real estate listings, it depends on the measurement standard used; in the US, ANSI Z765 generally includes closets within a room but excludes garages and unfinished areas, so a listed square footage can differ from a simple tape-measure total of every room.

What is price per square foot and how is it calculated?

Price per square foot is the total price of a property or job divided by its total square footage. For a home listed at $360,000 with 2,400 sq ft, that's $360,000 ÷ 2,400 = $150 per sq ft. It's a quick way to compare properties or quotes of different sizes on a like-for-like basis.

Do UK estate agents measure in square feet or square metres?

UK property listings are legally required to show floor area in square metres under the Material Information / Consumer Protection rules, but many agents also quote square feet alongside it, since some buyers still think in imperial terms for room sizes. This calculator lets you work in either unit and convert instantly between the two.

How many square feet is a typical UK semi-detached house?

A typical three-bedroom semi-detached house in the UK is often somewhere around 900 to 1,100 sq ft (roughly 84 to 102 m²), though this varies a lot by region and age of the property. Measuring room by room with this calculator and adding the totals is the most reliable way to get an accurate figure for your specific home.

Square Footage Calculator — Calculate Room Area in Sq Ft | UK

How to Calculate Square Footage

Square footage is simply the area of a space expressed in square feet — and for a plain rectangular room, it's one of the easiest measurements in construction or real estate to get right. Multiply the length of the room by its width, both measured in feet, and the result is the square footage. It sounds trivial, but getting it wrong by even a few inches per wall can throw off a flooring order, a paint estimate, or a listed home size by a meaningful margin.

This calculator does the multiplication for you and handles the fiddly parts: mixed units (measure in inches or metres and still get a clean square-foot answer), multiple identical rooms or lots in one pass via the quantity field, and a rough cost estimate if you're budgeting for a professional measurement or survey rather than a DIY tape-measure job.

People reach for a square footage calculator for a few different reasons. Homeowners and renters want to know how much flooring, carpet, or paint to buy before a renovation. Real estate agents and buyers use it to sanity-check a listed home size or compare price-per-square-foot across properties. Contractors use it as the first step in almost every material takeoff — you can't order drywall, tile, or insulation without knowing the area first.

Whatever the reason, the math underneath is the same: length times width. Below, we walk through exactly how the calculator's inputs map onto that formula, work a full example by hand, and cover the measuring mistakes that trip people up most often.

How to Use the Square Footage Calculator

Measure the length of the room or area in a straight line, wall to wall, and enter it in the Length field. Pick the unit you measured in (feet, metres, inches, etc.) from the unit dropdown next to it — the calculator converts automatically.
Measure the width the same way — perpendicular to the length — and enter it with its own unit in the Width field.
If you have several identical rooms or lots (say, four bedrooms of the same size, or repeating units in an apartment block), enter that count in the Number of identical rooms/areas field. Leave it at 1 for a single space.
Choose your preferred output unit for the area result (square feet, square metres, square yards, acres, or hectares) if you want something other than the calculator's default.
Read off the total square footage instantly. If a cost estimate is shown, it reflects a typical professional measurement/survey callout for your country, not a material price — this tool measures area, it doesn't price flooring or paint.

The Square Footage Formula

The formula for square footage is area = length × width, where both dimensions are in feet and the result comes out in square feet (sq ft, or ft²). This is the standard formula for any rectangle, and a room or lot only needs to be reasonably rectangular for it to apply directly.

Worked example: say you're measuring a bedroom that's 12 feet long and 10 feet wide. Square footage = 12 ft × 10 ft = 120 sq ft. If you had four identical bedrooms of that size in a new-build project, you'd multiply again by the quantity: 120 sq ft × 4 = 480 sq ft total.

If you measured in a different unit — say centimetres, because that's what your tape measure defaults to — the calculator converts each dimension to a common base unit before multiplying, then converts the resulting area into whichever output unit you've chosen. So a room measured as 366 cm by 305 cm converts to roughly 12.01 ft by 10.01 ft internally, giving essentially the same 120 sq ft result, or 11.15 m² if you switch the output to square metres. The key relationship to keep in your head: 1 square metre ≈ 10.764 square feet, and 1 square foot ≈ 0.0929 square metres.

This is also why unit consistency inside a single calculation matters more than which unit you personally prefer: the calculator handles the conversion, but if you're doing quick mental math on site, always convert both length and width to the same unit before multiplying — mixing feet and inches without converting is the single most common source of a wildly wrong square footage figure.

Typical Room Sizes for Reference

These are common approximate room sizes used in US/Canadian residential construction, useful as a sanity check against your own measurement (source: typical builder floor plans and the American Institute of Architects' residential space-planning guidance):

Standard bedroom: roughly 10 ft × 10 ft to 12 ft × 12 ft (100–144 sq ft)
Primary/master bedroom: roughly 14 ft × 16 ft (≈224 sq ft) or larger
Living room: roughly 12 ft × 18 ft to 16 ft × 20 ft (216–320 sq ft)
Kitchen: roughly 10 ft × 12 ft to 12 ft × 14 ft (120–168 sq ft)
Standard single-car garage: roughly 12 ft × 20 ft (≈240 sq ft)
Bathroom (full): roughly 5 ft × 8 ft (≈40 sq ft)

Pro Tips and Common Mistakes

Measure at floor level, not at a doorway or along a wall with a bump-out — walls are rarely perfectly parallel, so measure in at least two places and use the larger figure if they differ by more than an inch or two.

If you need a professional measurement rather than measuring yourself — for example, a surveyor or quantity surveyor measuring up a residential room or property in the UK — typical costs run from about £120 to £350, depending on property size and location.

Splitting irregular rooms: for an L-shaped room, alcove, or bay window, split the space into two or more rectangles, calculate each one's square footage separately, and add the results together. This calculator's quantity field can double as a quick way to total repeated identical rectangles, but for differently-sized sections you'll need to run the calculation more than once and add manually.
Don't forget closets and alcoves if you're measuring "usable" floor area for flooring or carpet — they usually need covering too, even if they're excluded from a real estate listing's "living area" figure.
Round up your final material order, not your measurement — measure as precisely as you can, then add a waste allowance (commonly 10% for straight flooring, more for diagonal patterns or tile) at the purchasing stage rather than padding the raw square footage number itself.
For real estate purposes, be aware that "square footage" on a listing may follow a specific measurement standard (like ANSI Z765 in the US) that excludes garages, unfinished basements, and some sloped-ceiling areas — a hand-measured total from this calculator is a great sanity check but may differ slightly from an official appraisal figure.
Common mistake: measuring along a wall that has a closet, chimney breast, or built-in unit protruding into the room. Always measure the actual clear floor dimension, not the wall-to-wall exterior dimension, if there's an obstruction.