Square Footage Calculator
Calculate the area of any space by shape. Add multiple areas together for irregularly shaped rooms or properties.
Area
Last updated: April 7, 2026· Reviewed by the CalcNeeds Team
About This Calculator
This square footage calculator finds the area of a room, lot, wall, ceiling, or any other surface in square feet, square meters, square yards, and acres. It supports four common shapes — rectangle, circle, triangle, and trapezoid — and you can add multiple shapes together to measure an irregularly shaped space like an L-shaped room or a pie-slice yard.
Square footage is the most common way to describe the size of homes, apartments, offices, and pieces of land in the United States. It's also the unit you'll need when buying flooring, tile, paint, sod, gravel, drywall, or just about any building material sold by area. Get the square footage right and the rest of your project becomes easy math.
How to calculate square footage of a room
For a standard rectangular room, multiply the length by the width in feet. A 12 ft × 14 ft room is 168 sq ft. If your room isn't a perfect rectangle, divide it into rectangles, calculate each one separately, and add the results. For closets, alcoves, or bay windows, measure them as their own small rectangle and add (or subtract, in the case of an interior column) from the total.
Always measure to the inside of the walls — that's the "net" or usable square footage. The "gross" square footage real estate listings sometimes use includes wall thickness and is typically 10–15% larger.
Square footage formulas for every shape
Rectangle: Area = Length × Width. The standard formula for rooms, walls, decks, and most flat surfaces.
Circle: Area = π × r². Enter either the radius (distance from center to edge) or the diameter (full width) in feet. Useful for circular patios, pools, fire pits, and round garden beds. π ≈ 3.14159.
Triangle: Area = ½ × Base × Height. The base is any one side, and the height is the perpendicular distance from that side to the opposite corner — not the length of the slanted side. Use this for triangular roof sections, gable walls, and pie-slice yard portions.
Trapezoid: Area = ½ × (Side A + Side B) × Height. Side A and Side B are the two parallel sides; Height is the perpendicular distance between them. Useful for lots that taper and rooms with one angled wall.
L-shape or irregular shape:Break it into rectangles or trapezoids, calculate each one, and add the totals. This calculator's "Add Area" button lets you stack multiple shapes into a single grand total.
Converting square feet to other units
Square feet to square meters: multiply by 0.0929, or divide by 10.7639. A 1,500 sq ft house is about 139.4 sq m.
Square feet to square yards: divide by 9. A 180 sq ft room is 20 sq yd, the unit carpeting is often sold in.
Square feet to acres: divide by 43,560. A 10,000 sq ft lot is about 0.23 acres.
Square inches to square feet: divide by 144 (since there are 12 × 12 inches in one square foot).
This calculator converts to all four units automatically once you enter your measurements.
Why square footage matters for buying materials
Most building materials are priced per square foot. Once you know the area, you can estimate exactly how much you need (and what it will cost) for tile, hardwood, laminate, carpet, vinyl plank, sod, paint, drywall, gravel, mulch, and more. Always add a 10% waste factor for square or rectangular layouts and 15% for diagonal or patterned layouts to cover cuts, breakage, and mistakes.
Frequently Asked Questions
How do I calculate the square footage of a room?
Multiply the length by the width in feet. A 10 ft × 12 ft room is 120 sq ft. For non-rectangular rooms, divide the floor plan into rectangles, calculate each one, and add them together. The calculator above lets you stack multiple shapes into a single total.
How many square feet is a 12 × 12 room?
144 square feet. The formula is length × width, so 12 × 12 = 144 sq ft. A 10 × 10 room is 100 sq ft, a 12 × 14 room is 168 sq ft, and a 12 × 32 area is 384 sq ft.
How do I find the square footage of an irregular shape?
Break the shape into rectangles, triangles, trapezoids, or circles, calculate the area of each piece, and add them together. For example, an L-shaped room can be split into two rectangles. The calculator above has an 'Add Area' option that lets you stack multiple shapes into a single grand total.
How do I calculate the square footage of a building?
Measure each room separately (length × width), then add all the rooms together. Most measurement standards (like ANSI Z765 used by U.S. real estate) measure to the exterior of perimeter walls and exclude unfinished basements, attached garages, and porches that aren't conditioned. For a quick estimate, multiply the building's outside length by its outside width.
How many square feet are in an acre?
1 acre = 43,560 square feet. To convert square feet to acres, divide by 43,560. A standard quarter-acre lot is 10,890 sq ft, and a half-acre is 21,780 sq ft.
How do I convert square feet to square meters?
Multiply the square footage by 0.0929, or divide by 10.7639. A 1,000 sq ft apartment is approximately 92.9 sq m. The calculator above shows the metric conversion automatically.
What's the difference between square feet and linear feet?
A linear foot is a measure of length — one foot in a straight line. A square foot is a measure of area — a 1 ft × 1 ft square. You can't directly convert between them without knowing the width: a 10 ft × 1 ft strip is 10 linear feet but also 10 square feet, while a 10 ft × 4 ft strip is still 10 linear feet but 40 square feet.
How much extra material should I buy for a flooring project?
Add 10% to your square footage for standard rectangular installations to cover cuts and waste, and 15% for diagonal installations or patterned tile. For very irregular rooms, go up to 20%. Buy enough that you won't have to source matching material later from a different dye lot or production batch.
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