Square Footage Calculator — Area of Rooms and Shapes

How to use the calculator

Keep Imperial (ft) selected. All dimensions are then in feet; use decimals for inches (6 in = 0.5 ft).
Choose the shape and fill in the fields it shows:
- Rectangle: A = length, B = width.
- L-shape: split it into two rectangles that don't overlap. A × B is the first, C × D the second.
- Circle: A = diameter.
- Triangle: A = base, B = height measured at a right angle to the base.
- Trapezoid: A and C = the two parallel sides, B = the distance between them.
Under Advanced options, set a quantity if you have several identical areas, such as three bedrooms of the same size.
Optionally enter the price per square foot to see the total cost.

Formulas used

Rectangle: A × B. Perimeter = 2 × (A + B).
L-shape: A × B + C × D.
Circle: π × A² ÷ 4. Perimeter (circumference) = π × A.
Triangle: A × B ÷ 2.
Trapezoid: (A + C) ÷ 2 × B.

The area is multiplied by the quantity, and the cost is area × price. Conversions follow NIST: 1 ft = 0.3048 m exactly, so 1 sq ft = 0.09290304 m², and 1 sq yd = 9 sq ft. The perimeter appears only for rectangles and circles; for other shapes, add up the sides yourself.

Worked examples

1. Bedroom, 15 × 12 ft

Area 180 sq ft, which is 20 sq yd or 16.72 m². The perimeter is 54 ft, useful for baseboard. At $4.50 per sq ft for flooring, the material comes to $810.00 before waste.

2. L-shaped living room

Split into a 20 × 12 ft section and a 10 × 8 ft section: 240 + 80 = 320 sq ft (35.56 sq yd, 29.73 m²). At $4.50 per sq ft: $1,440.00.

3. Round patio, 10 ft across

A = 10 ft gives 78.54 sq ft and a circumference of 31.42 ft for edging.

4. Trapezoid lot

Parallel sides of 30 and 24 ft, 20 ft apart: 540 sq ft, or 60 sq yd.

5. Three identical rooms

Three 10 × 10 ft bedrooms with quantity 3: 300 sq ft in total.

Getting an accurate number

Measure wall to wall at floor level, and round up to the next inch rather than down. For irregular rooms, sketch the floor plan and split it into rectangles and triangles; run the calculator for each piece and add the results. Closets count if you are covering them too.

The result is the net area. When you buy flooring, tile or sod, the store or installer will usually add a waste allowance for cuts, so the quantity you buy is larger than the area shown here.

Frequently asked questions

How do I calculate the square footage of a room?

Multiply the length by the width in feet. A 15 × 12 ft room is 180 sq ft. For an L-shaped room, split it into two rectangles and add their areas.

How do I convert inches to feet before calculating?

Divide inches by 12: 6 in is 0.5 ft and 3 in is 0.25 ft. A room of 12 ft 6 in by 10 ft is 12.5 × 10 ft, or 125 sq ft.

How many square feet are in a square yard?

Nine, because a yard is 3 ft and 3 × 3 = 9. The calculator shows sq yd next to sq ft, so a 180 sq ft room reads as 20 sq yd.

How do I convert square feet to square meters?

Multiply by 0.09290304. A 12 × 10 ft room of 120 sq ft is 11.15 m². The calculator shows both automatically.

How do I work out the cost per square foot?

Enter the price per sq ft and the calculator multiplies it by the area. A 12 × 10 ft room at $3.25 per sq ft costs $390.00. To find the price per sq ft of a quote, divide the total by the area instead.

How do I measure the area of a circle?

Measure the diameter, the widest distance across through the center, and choose Circle. A 10 ft circle covers 78.54 sq ft.

Sources

The results are geometric areas based on the measurements you enter. Check measurements on site before ordering materials, and add the waste allowance your supplier recommends.

Results