Square Footage Calculator

How to measure square footage

Square footage is the area of a floor or surface in square feet. To measure it, pick a unit (a tape measure in feet is easiest for most rooms), get the dimensions of the space, multiply or apply the appropriate formula for the shape, then sum the parts if the room isn't a single rectangle. A few tricks that catch people out:

• Measure twice. A 1 % error on a 200 sq ft room costs you a yard of material — quick to fix on paper, expensive at the supply yard.
• Use the right unit. Mixing feet and inches in one room is the most common source of error. The calculator's unit toggle stops that from happening.
• Break L-shaped rooms into rectangles. The "Irregular" mode is built for this — add one rectangle per section.
• Don't forget the kicker spaces. Closets, bay windows and alcoves all add square footage that flooring needs to cover.

Formulas by shape

Rectangle / square    area = length × width
Circle                area = π × radius²        (or π × diameter² / 4)
Triangle              area = (base × height) / 2
Trapezoid             area = ((side_a + side_b) / 2) × height
Irregular             area = Σ (length_i × width_i)
Multi-room            area = area × quantity
With waste            area_with_waste = area × (1 + waste% / 100)
Cost                  cost = area_with_waste × price_per_sq_ft

Examples

• Standard bedroom (10 × 12 ft): 120 sq ft. With a 10% flooring waste factor, buy 132 sq ft. At $4/sq ft hardwood, ~$528.
• Round patio (10 ft diameter): π × 5² ≈ 78.5 sq ft. With 15% tile waste, buy 91 sq ft.
• L-shaped living room: 12 × 18 ft main + 6 × 8 ft alcove = 216 + 48 = 264 sq ft. With 10% carpet waste, buy 291 sq ft.

Conversion chart

FAQ

How do I calculate square footage?

For a rectangular room, multiply length by width. Both numbers must be in the same unit; the result is in that unit squared. For other shapes use the appropriate formula: π × r² for a circle, (base × height) / 2 for a triangle, ((a + b) / 2) × height for a trapezoid, sum of rectangles for an irregular shape.

How many square feet is a 10 × 10 room?

A 10 ft × 10 ft room is 100 square feet. In metric that is 9.29 m². With a typical 10% waste factor for flooring you would buy 110 sq ft to cover it.

How do I measure irregular rooms?

Break the floor plan into rectangles. Measure each rectangle and add the areas. The calculator's "Irregular" mode does this for you: one row per rectangle, dimensions in the chosen unit. Closets, alcoves and bay windows each become their own rectangle.

Does square footage include closets?

For flooring estimates, yes — you want to buy enough to cover them. For real-estate listings, closets are sometimes included and sometimes excluded depending on jurisdiction; check local rules. The calculator gives you the total floor area; what you do with it is up to you.

What waste factor should I use?

10% is the standard for most flooring, carpet, paint and roofing. Tile and stone go up to 15% because of cuts at edges and diagonal patterns. Lawn and sod can drop to 5% because it cuts cleanly. The Material dropdown sets a sensible default for each.

How do I convert square feet to square meters?

Multiply square feet by 0.0929. So 100 sq ft ≈ 9.29 m². The opposite direction is multiply by 10.7639. The calculator shows the conversion automatically.

Related calculators

• Paint Coverage Calculator — how much paint for a given area.
• 2D Panel Cut Optimizer — when the area is a single sheet to cut from.
• 1D Cut List Optimizer — for boards, pipes and linear stock.

Privacy

Every calculation runs in your browser. Your room dimensions never leave your device — nothing is sent to a server, nothing is stored in cookies, nothing is logged. The only thing this site remembers is whether you prefer feet, inches, yards, meters or centimeters, kept locally so you don't have to toggle it every visit.