Construction

Square Footage Calculator

Add one area per room or section. Mix shapes and units freely — everything is converted to square feet and totalled, with square meters and a materials allowance alongside.

Mix shapes and units in the same calculation — everything is converted before it is added.

The formulas

Shape	Formula	Use it for
Rectangle	`area = length × width`	Most rooms, walls, decks and lawns.
Square	`area = side × side`	A single side is enough.
Triangle	`area = (base × height) ÷ 2`	Gable ends, corner lots, angled patios.
Circle	`area = π × (diameter ÷ 2)²`	Round patios, pools and planters. Enter the diameter.
Rectangle with a cut-out	`area = (outer length × outer width) − (cut-out length × cut-out width)`	A room minus an island, or a lawn minus a shed.

Odd-shaped rooms are handled by splitting them into rectangles: an L-shaped room is two areas, and an alcove is a third. That is what the "add another area" button is for, and it is exactly how a contractor would measure it.

How to measure a room properly

Measure at floor level, along the baseboards, not at waist height where furniture gets in the way.
Measure twice, at both ends of the room. Walls are rarely parallel in older buildings; use the larger figure for materials.
Work in one unit. If you measure in feet and inches, convert the inches — 12 ft 6 in is 12.5 ft, not 12.6.
Split the room at any change of width, then add the pieces.
Subtract only large fixed obstructions — a kitchen island or a staircase. Do not subtract a doorway; you will need the material anyway.

Formula12 ft 6 in = 12 + (6 ÷ 12) = 12.5 ft

Square feet, square meters and square yards

Area units square up, which is why the conversion numbers look unfamiliar. One foot is 0.3048 meters, so one square foot is 0.3048² = 0.092903 m². One square yard is 9 square feet, not 3 — a mistake that gets made on carpet orders constantly.

From	To	Multiply by
Square feet	Square meters	0.092903
Square meters	Square feet	10.7639
Square feet	Square yards	÷ 9
Square feet	Acres	÷ 43,560

Waste allowance — how much extra to buy

The area of your floor is not the amount of material to order. Cuts, offcuts, pattern repeats and mistakes all eat into a box.

5% — plain material, a simple rectangular room, straight layout.
10% — the usual default, and what most flooring manufacturers recommend.
15% — diagonal or herringbone layouts, patterned material that has to line up, or a room with many angles.
20% — large-repeat patterns, or a first attempt at a tricky install.

Order the whole allowance in one go, from one batch. Tile and laminate colours shift slightly between production runs, so a top-up box bought a month later may not match.

Worked examples

A 12 ft by 10 ft bedroom

12 × 10 = 120 sq ft, or 11.15 m². With a 10% waste allowance, order for 132 sq ft.

An L-shaped living room, 20 × 14 ft with a 6 × 8 ft section missing

Use the rectangle with a cut-out shape: 280 − 48 = 232 sq ft.

A round patio 10 ft across

π × 5² = 78.54 sq ft. Diameter goes in the box, not the radius — halving it is the step people forget.

Four identical 8 × 8 ft closets

Enter one 8 × 8 area with a quantity of 4: 256 sq ft.

Common uses

Flooring: laminate, tile, carpet, vinyl and underlay.
Paint: wall area, using the wall's height and width as a rectangle.
Landscaping: turf, mulch, gravel and patio slabs.
Property listings: total floor area from room measurements.
Concrete: the slab area that feeds into the concrete calculator.

Frequently asked questions

How do I calculate the square footage of a room?

Multiply the length by the width in feet. A 12 by 10 foot room is 120 square feet. If the room is not a simple rectangle, split it into rectangles, work each one out, and add them together.

How do I handle feet and inches?

Convert the inches to a decimal by dividing by 12. 12 feet 6 inches is 12.5 feet, and 8 feet 3 inches is 8.25 feet. Entering 12.6 for 12 ft 6 in is the single most common measuring error.

How many square feet are in a square meter?

10.7639. Going the other way, one square foot is 0.092903 square meters. Both figures are shown for every result, so you never have to convert by hand.

Should I subtract doorways and closets?

Subtract large permanent obstructions like a kitchen island or a staircase. Do not subtract doorways — you generally run flooring through them, and the material is needed anyway. Closets are usually measured as their own separate area.

How much extra material should I order?

10% is the standard allowance for a straightforward install, 15% for diagonal or patterned layouts. Put the figure in the waste box and the calculator gives you the amount to actually buy alongside the true area.

Can I mix units between areas?

Yes. Each area has its own unit selector, so you can measure a room in feet and a hallway in meters. Everything is converted to square feet before being added together.