Square Footage Calculator

What this calculator does

The Square Footage Calculator measures the area of a floor, lot, wall, or other flat surface. It supports three layouts: a plain rectangle, an L-shaped space made from two rectangles, and a room that also needs wall and ceiling areas. Every result includes square feet plus conversions to square yards, square meters, and acres.

Square footage is used constantly in construction and real estate. Paint, flooring, tile, roofing, and landscaping are priced by area, and lease or appraisal documents often quote square feet. Measuring the same space twice and comparing the results is a simple way to catch a tape-measure error before ordering materials.

How to use this calculator

1. Choose Rectangle, L-shape, or Room.
2. For a rectangle, enter length and width in feet. Enter how many identical areas you have, if more than one.
3. For an L-shape, enter the main rectangle and the extension rectangle. The two rectangles must not overlap.
4. For a room, enter length, width, and wall height to get floor area, wall area, ceiling area, perimeter, and volume.
5. Click Calculate.

The default rectangle is 30 feet by 20 feet, which returns 600 square feet. The same area is 66.67 square yards, 55.74 square meters, or 0.01377 acres.

Square footage formulas

Rectangle area = length × width × quantity
L-shape area   = (main length × main width
                  + extension length × extension width) × quantity
Room floor     = length × width
Room perimeter = 2 × (length + width)
Room wall area = perimeter × wall height
Room ceiling   = floor area
Room volume    = floor area × wall height

Conversions used by the result panel:

square yards  = square feet ÷ 9
square meters = square feet ÷ 10.7639104167
acres         = square feet ÷ 43,560

Assumptions and limitations

• All length inputs are in feet. The calculator does not mix feet and inches in one dimension.
• The L-shape is modeled as two non-overlapping rectangles. An L-shape with a cutout that cannot be split this way needs a different method.
• The room method assumes a rectangular room with four walls and a flat ceiling. It does not subtract doors, windows, or openings from the wall area.
• The room volume is a simple rectangular volume. Sloped ceilings, bay windows, and irregular alcoves are not modeled.
• Quantity applies to the rectangle and L-shape methods, not the room method.
• Results are rounded only for display. Use the square-foot value as the ordering quantity and add a waste allowance for materials.

Frequently asked questions

How do I measure an L-shaped room?

Split the L into two rectangles that do not overlap. Measure the length and width of each rectangle, multiply them, and add the two areas. Our L-shape mode performs that addition for you.

How many square feet are in an acre?

One acre is 43,560 square feet. A square lot that measures about 208.7 feet on each side is exactly one acre.

Does wall area include windows and doors?

No. The wall area is the perimeter multiplied by the wall height. Subtract the area of large windows and doors yourself if you are buying paint or siding and want a net surface area.

Reference table

Example area conversions

Measure each rectangular section separately, then add the areas. For irregular rooms, split the shape into rectangles and triangles.

Source

Reference: Calculator.net — Square Footage Calculator.

This calculator provides geometric estimates. Measure twice before ordering flooring, paint, or landscaping materials.