Square Feet Calculator: Square Footage & Cubic Yards

How to Calculate Square Feet

This square foot calculator works out the area of a room, lot, bed or any shape you can measure. Here is how to calculate square footage in a few steps:

Pick the shape that matches your space. Rectangle covers most rooms, and circle, triangle and trapezoid cover the rest.
Measure each dimension. You can use feet, inches, yards, millimeters, centimeters or meters, and mix them in one calculation.
Enter the values. The calculator converts everything to feet and applies the formula for your shape.
Press Calculate, then read the area in square feet, plus square yards, square meters and acres.
If you also need a volume, open the optional section and enter a depth to get cubic feet and cubic yards.

Press Calculate after each change, so it is quick to compare options, such as two room layouts, before you buy flooring or paint.

Area Formulas for Every Shape

The calculator applies the formula for whichever shape you choose. Every length is converted to feet first, so the result comes out in square feet.

Rectangle

Rooms, decks, lawns and walls.

Area = L × W

L = length (ft) · W = width (ft)

Example: L = 14 ft, W = 12 ft. Area = 168 ft², or 18.67 yd².

Square

Square rooms, tiles and patio pads.

Area = S × S

S = side length (ft)

Example: S = 10 ft. Area = 100 ft², or 11.11 yd².

Circle

Round patios, rugs and tabletops.

Area = π × (Ø ÷ 2)²

Ø = diameter (ft)

Example: Ø = 12 ft. Area = 113.1 ft², or 12.57 yd².

Triangle

Gable ends and corner plots.

Area = ½ × B × H

B = base (ft) · H = triangle height (ft)

Example: B = 20 ft, H = 8 ft. Area = 80 ft², or 8.89 yd².

Trapezoid

Angled lots and bay window areas.

Area = ½ × (B₁ + B₂) × H

B₁ = base 1 (ft) · B₂ = base 2 (ft) · H = trapezoid height (ft)

Example: B₁ = 30 ft, B₂ = 20 ft, H = 15 ft. Area = 375 ft², or 41.67 yd².

Rectangle Border

A tile or carpet border around a room.

Area = (L + 2b) × (W + 2b) − L × W

L = inner length (ft) · W = inner width (ft) · b = border width (ft)

Example: L = 12 ft, W = 10 ft, b = 1 ft. Area = 48 ft², or 5.33 yd².

Circle Border

Edging around a round patio.

Area = π × ((Ø ÷ 2 + b)² − (Ø ÷ 2)²)

Ø = inner diameter (ft) · b = border width (ft)

Example: Ø = 10 ft, b = 2 ft. Area = 75.4 ft², or 8.38 yd².

Annulus (Ring)

A ring path around a fountain or tree.

Area = π ÷ 4 × (Ø₁² − Ø₂²)

Ø₁ = outer diameter (ft) · Ø₂ = inner diameter (ft)

Example: Ø₁ = 10 ft, Ø₂ = 4 ft. Area = 65.97 ft², or 7.33 yd².

L shapes and irregular spaces

Split the space into rectangles and other simple shapes, calculate each one, and add the areas. If several pieces are the same size, enter one and use the quantity field to multiply it.

Square Feet to Cubic Yards Calculator: How the Conversion Works

People often search for a square feet to cubic yards calculator, but the two units measure different things. Square feet are a surface and cubic yards are a volume, so you cannot convert square footage to cubic yards without one more number: the depth. Once you have it, the sum is short.

Cubic feet = square feet × depth (ft)

Cubic yards = cubic feet ÷ 27

Shortcut: cubic yards = square feet × depth (in) ÷ 324

This page can give cubic yards as well. Open the optional section above, enter a depth, and you get the cubic yards from square feet in the same result card. If all you need is a volume, the cubic yard calculator has a Known Area option for exactly that.

Quick reference: square footage to cubic yards

Cubic yards for common square footages and depths
Area	3 in deep	4 in deep	8 in deep
150 sq ft	1.39 yd³	1.85 yd³	3.7 yd³
300 sq ft	2.78 yd³	3.7 yd³	7.41 yd³
750 sq ft	6.94 yd³	9.26 yd³	18.52 yd³
1,500 sq ft	13.89 yd³	18.52 yd³	37.04 yd³

Which calculator fits which material?

Different materials have their own habits, so each has its own page. Use the Mulch Calculator for beds, the Topsoil Calculator for lawns and gardens, the Gravel Calculator and Sand Calculator for bases, and the Concrete Calculator for slabs. The cubic yard calculation guide explains the math behind all of them.

Area Unit Conversions

1 ft² = 144 in²

1 yd² = 9 ft²

1 m² ≈ 10.7639 ft² (1 ft² = 0.09290304 m²)

1 acre = 43,560 ft²

Areas use the square of the length conversion. Because 1 ft = 12 in, 1 ft² = 12 × 12 = 144 in². Likewise 1 yd = 3 ft, so 1 yd² = 3 × 3 = 9 ft².

Square Feet Calculator Examples

These examples come from the same code as the calculator above, so you can type in the same numbers and compare.

Room: 12 ft × 15 ft

Length times width gives the floor area.

Area = 180 ft² = 20 yd² = 16.72 m²

Mixed units: 10 ft × 120 in

120 inches is 10 feet, so the area is 10 × 10. There is no need to convert before typing.

Area = 100 ft² = 11.11 yd² = 9.29 m²

Circle: 10 ft across

The area of a circle is π × (diameter ÷ 2)² = π × 5².

Area = 78.54 ft² = 8.73 yd² = 7.3 m²

Metric: 4 m × 3 m

Metric inputs are converted exactly (1 ft = 0.3048 m) and shown in square feet too.

Area = 129.17 ft² = 14.35 yd² = 12 m²

Square feet to cubic yards: 12 ft × 15 ft at 4 in deep

Enter the depth in the optional section. The 180 ft² area times 0.3333 ft gives the volume, which is then divided by 27.

Area = 180 ft² = 20 yd² = 16.72 m². Volume: 180 ft² × 0.3333 ft = 60 ft³ ÷ 27 = 2.22 yd³

Adding Extra for Cuts and Waste

Flooring, tile, paint and turf are often bought with extra to allow for cuts and mistakes. The waste field is optional and starts at 0%. Enter your own percentage and the result shows the area including that allowance, along with the cost if you add a price. If you have entered a depth, the cubic yards include the allowance too.

Tips for Measuring Accurately

Measure each wall or edge rather than assuming opposite sides match.
Sketch the space and label every side before you start so no section gets missed.
Write the unit next to each number, since mixing feet and inches is the usual slip.
Subtract nothing for small obstacles unless you are sure the material will not go there.
For a curved edge, measure the width at several points and use the average.

Square Feet Calculator FAQ

How do I calculate square feet?

For a rectangle, multiply the length by the width, both in feet. For other shapes, use the formula on its shape card above, or pick the shape in the calculator and enter its sizes.

How do I convert square footage to cubic yards?

You need a depth, because square feet measure a surface and cubic yards measure a volume. Multiply the square footage by the depth in feet, then divide by 27. With the depth in inches, multiply the square footage by the depth and divide by 324.

How do I convert square inches to square feet?

Divide by 144, because one square foot is 12 inches by 12 inches. Do not divide by 12; that works for lengths, not areas.

How many square feet are in a square yard?

Nine. A square yard is 3 ft × 3 ft = 9 ft².

How do I measure an L shaped or irregular room?

Split it into rectangles, find each area and add them. A 12 ft × 10 ft section (120 ft²) plus a 6 ft × 4 ft section (24 ft²) is 144 ft². The quantity field helps when several sections are identical.

Should I add extra for flooring, paint or sod?

Cuts, patterns and trimming mean many people buy extra. The optional waste field adds the percentage you choose to the area and the cost. It is 0% unless you enter a value.

See all calculators and which one fits your project →