Square Footage Calculator - Room Area, Flooring & Cost

Rectangle

For a rectangle line

Rectangle

the rectangle’s area

Source: Uses the formula in [4]: length × width. The perimeter is its four sides.

Triangle by its base and height

For a triangle by its base and height

Triangle

the triangle’s area

The height is measured at right angles to the base, not along a sloping side. It has no perimeter: its other two sides depend on where its top is, so give its three sides for one.

Source: Uses the formula in [4]: 0.5 × base × perpendicular height.

Triangle by its three sides

For a triangle by its three sides

Triangle

the triangle’s area

Heron’s formula, worked in the order Kahan gives, with the sides sorted so a ≥ b ≥ c. That order, ¼ × √((a + (b + c)) × (c − (a − b)) × (c + (a − b)) × (a + (b − c))), is the same area. It keeps the digits a long, thin triangle would lose. Three sides whose longest is not shorter than the other two together make no triangle, and the line says so.

Source: Standard formula; no single publisher. The stable order and the test for sides that make no triangle are in [5].

Circle

For a circle line

Circle

the circle’s area

Source: Based on [4], which writes it as 0.7854 × diameter × diameter, and the circumference as 3.1416 × diameter. CalcTrail uses π in full, so a 10 ft circle is 78.54 ft² and 31.42 ft around either way, to two decimals.

Half circle

For a half-circle line

Half circle

half a circle’s area

For a bay or an arch: the diameter is the straight side across its opening. Its perimeter is the curve and that straight side.

Source: Half of the circle in [4]; standard formula, no single publisher.

Feet and inches

In feet and inches

The inches may be more than 12: 0 ft 133 in is 11.083 ft.

Source: Uses 12 in = 1 ft from [3]. The foot is the international foot, 0.3048 m exactly [1].

Lines and the area

Line area

one shape’s area × its count

Area

the measured area

Each line is worked in the unit it was measured in, and the lines are added before anything is converted. Lines taken off must leave an area: when they come to as much as the lines added, or more, the result says so instead of showing a negative area. A line with an error holds the total until it is fixed.

Source: Standard arithmetic; no single publisher. Measuring a surface as simple shapes added together is how [9] measures walls: each wall’s height × width, added, less large windows and doors.

Perimeter, for trim

With a perimeter

Perimeter

the edges of the lines added, for baseboard and other trim

Lines taken off are left out, and so are doorways. Each line counts its own edges, so where two lines share one, as an L-shaped room split in two, that edge is in both: take it off twice. Shown in feet and in meters, 1 ft = 0.3048 m.

Source: Perimeter as [4] defines it, the line forming the boundary of a closed figure; standard arithmetic, no single publisher.

Square meters and square yards

Both exact: 0.09290304 is 0.3048², and 1 yd² = 9 ft² = 0.83612736 m². An area measured in meters is turned into square feet by the same factor.

Source: Uses the factor in [2], printed there as exact, and 1 yd² = 9 ft² from [3].

Area to order

With a waste allowance

Area to order

the area with the waste added

Area

the measured area

Waste

your allowance for cuts, in percent

Your own percentage, added once to the total, not to each line. Makers commonly advise about 5% for a plain room and 10% for one with many angles or curves [6], up to 15% depending on the product [12], and more for diagonal, herringbone or bordered layouts [7].

Source: Your own figure; the advice is the makers’ own, for their floors: [6], [12] and [7].

Whole boxes

With an area per box

Boxes

whole boxes to buy

Area per box

the area printed on one box

Area to order

the area with the waste added

Rounded up to the next whole box once, at the end, after the waste, so rooms are not each rounded up. The area per box is the one printed on the pack, in ft² or m²; it is not worked out from the size of the planks.

Source: Flooring is packaged by a stated area [8]. Rounding up to whole boxes is standard arithmetic; no single publisher.

Spare boxes

With spare boxes

Boxes to buy

the whole boxes you buy

Boxes

whole boxes by area

Spare boxes

your boxes kept for repairs

Your own number, added after the boxes are rounded up, never folded into the waste. A cost by the box, or of what the boxes cover, includes them.

Source: Mannington advises keeping extra material for possible repairs [12]; adding the boxes is standard arithmetic.

Cost

With a price per area

Cost

what is bought, at your price

Area bought

what the whole boxes cover, or the area to order without boxes

Price per area

your price per ft², m² or yd²

With an area per box the cost is of the whole boxes, what you pay for, and not of the bare area. The price is also shown per ft², per m² and per yd²: 1 yd² is 9 ft² and 0.83612736 m².

Source: Standard arithmetic; no single publisher.

Cost by the box

With a price per box

Cost

what is bought, at your price

Boxes

whole boxes to buy

Price per box

your price for one box

Source: Standard arithmetic; no single publisher.

A total quote per area

With a total quote

Price per area

the quote per ft², m² or yd²

Total quote

the whole price you were quoted

Area

the measured area

The same total is also divided by the area to order, by what the whole boxes cover and by the number of boxes.

Source: Standard arithmetic; no single publisher.

A listed area against your own

With a listed area

Listed area

the area a plan, a listing or an agreement gives

Area

the measured area

Arithmetic only: it never says which area is right. A listing may follow a method of its own: ANSI Z765 does not cover room dimensions [10], and India’s carpet area [11] leaves out external walls, service shafts and exclusive balconies and terraces. With a price, the total is divided by each area too.

Source: Standard arithmetic; no single publisher. What the two methods cover: [10], [11].