Square Feet Calculator

Calculate the square footage of any room or area — rectangles, L-shaped rooms, circles, walls with windows cut out, and seven more shapes — with a live diagram that redraws as you type. Built for homeowners, renters, DIYers, contractors and real estate agents who need fast, accurate square foot, square meter, and square yard results, plus a running total for multi-room flooring, paint, or tile projects.

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  • room size calculator
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  • square feet to square meters

Rectangle

0 sq ft

Enter dimensions to see your area.

Project total

No sections added yet. Calculate a shape above, then click “Add to project total” — useful for L-shaped, U-shaped, or multi-room jobs.

    Formulas used by this square footage calculator

    Every shape above uses a standard geometry formula. Reference the table below if you want to calculate by hand or double-check the tool's output.

    All linear inputs are converted to a common unit before these formulas are applied, so you can mix feet, inches, meters, etc. within one shape.
    ShapeFormulaWhen to use it
    RectangleA = L × WStandard square or oblong rooms, most bedrooms and living rooms.
    SquareA = S²A room or slab where all four sides are equal.
    CircleA = π × (d ÷ 2)²Round rugs, fountains, circular patios — measured by diameter.
    TriangleA = (b × h) ÷ 2Attic corners, gable walls, triangular lots.
    TrapezoidA = ((a + b) ÷ 2) × hRooms with one angled wall, some sunrooms.
    ParallelogramA = b × hSlanted walls where opposite sides stay parallel.
    EllipseA = π × (L ÷ 2) × (W ÷ 2)Oval rugs, oval pools, curved planters.
    L-ShapeA = (A₁ × B₁) − (C × D)L-shaped living rooms, rooms with a bumped-out closet or nook removed.
    Rectangle borderA = (L × W) − ((L − 2t) × (W − 2t))Picture frames, border tiling, a walkway around a rectangular patio.
    Circle ringA = π × (R² − r²)A circular walkway or border around a round feature.
    Wall minus window/doorA = (H × W) − (openings × h × w)Paintable wall area once doors and windows are excluded.

    How to measure square feet

    Getting an accurate square footage starts with careful measuring, not the math. Follow these steps for any room:

    1. Measure each dimension. Run a tape measure (or laser measurer) along the floor from wall to wall for length and width, or along the relevant edges for other shapes. Measure to the nearest half-inch for best accuracy.
    2. Convert units if needed. If your measurements are in inches, yards, or metric units, either convert to feet first or use this calculator's per-field unit selector — you can enter feet and inches in the same shape without doing the math yourself.
    3. Split irregular shapes into sections. For L-shaped, U-shaped, or multi-room spaces, break the space into simple shapes (rectangles, triangles, circles) that you can measure and calculate individually.
    4. Verify against the diagram. Check that the live diagram's proportions roughly match the real room — a diagram that looks far too wide or too narrow is a good sign a measurement or unit was entered wrong.
    5. Add each section to the project total. Use the "Add to project total" button after each section so the running total captures the whole space.
    6. Add a waste allowance for materials. If you're ordering flooring, tile, or carpet, add 10-15% in the waste factor field to cover cuts, offcuts, and pattern matching.

    Worked example: how many square feet is a 12×15 room?

    Say you measure a bedroom at 12 feet by 15 feet. Because a rectangular room's area is length times width, the calculation is:

    Length × Width = Area

    12 ft × 15 ft = 180 sq ft

    That's 180 square feet — roughly the size of a one-car garage. In square meters, that's 180 × 0.092903 ≈ 16.72 sq m. If you're ordering carpet and want a 10% waste allowance, you'd order enough material to cover 180 × 1.10 = 198 sq ft.

    What counts as square footage?

    This trips up a lot of homeowners and buyers, especially when comparing listings. In most US real estate contexts, "square footage" refers only to finished, heated, enclosed living space — think bedrooms, living rooms, finished bathrooms, and kitchens.

    Usually included: finished basements (in some regions), finished attics with adequate ceiling height, enclosed and heated sunrooms.

    Usually excluded: garages, unfinished basements, open or unheated porches, decks, and detached structures like sheds or guest houses — these are often listed separately as "additional" square footage rather than folded into the main total.

    Standards vary by appraiser, region, and country — in the US, ANSI Z765 is the most common residential standard. When in doubt for a real transaction, confirm with a licensed appraiser rather than relying on a self-measurement.

    Frequently asked questions

    How do I calculate the square feet of a room?

    Measure the length and width of the room in feet using a tape measure, then multiply length by width. For a room that is 12 feet long and 10 feet wide, the area is 12 × 10 = 120 square feet. If your room isn't a simple rectangle, split it into smaller rectangles or shapes, calculate each one separately, and add the results together.

    What is the difference between square feet and square footage?

    There is no real difference — "square feet" is the unit of measurement (like inches or miles), while "square footage" is the general term for the total area of a space measured in that unit. Saying a room "is 200 square feet" and saying a room "has 200 square feet of square footage" describe the exact same measurement.

    What is the difference between square feet and linear feet?

    Linear feet measure distance in a single straight line, such as the length of a wall or a piece of baseboard, and involve no multiplication. Square feet measure two-dimensional area (length times width) and are used for flooring, paint coverage, or room size. A wall can be 20 linear feet long, but the same wall might cover 160 square feet once you factor in its height.

    How do I calculate the square footage of an L-shaped room?

    Split the L-shaped room into two rectangles by extending one wall until it meets another, then measure and calculate each rectangle's area separately and add them together. Alternatively, measure the overall bounding rectangle of the room and subtract the area of the missing rectangular notch. Our calculator's L-Shape option does this second method automatically — just enter the outer dimensions and the notch dimensions.

    How do I convert square feet to square meters?

    Multiply the square footage by 0.092903 to get square meters. For example, 500 square feet × 0.092903 = 46.45 square meters. Our calculator shows both units simultaneously, along with square yards, square inches, square centimeters and acres, so you never need to do this conversion by hand.

    How many square feet is a 10x10 room?

    A 10 foot by 10 foot room is 100 square feet (10 × 10 = 100). This is a common size for a small bedroom, home office, or bathroom-plus-closet combination.

    How many square feet is a 12x12 room?

    A 12 foot by 12 foot room is 144 square feet (12 × 12 = 144). This is a typical size for a standard bedroom or a small-to-mid-size living room.

    How do I calculate square feet for flooring or carpet?

    Calculate the total floor area in square feet using the room's shape (or by adding up multiple sections for an irregular room), then add a waste allowance of roughly 10% for straight-lay materials like carpet, or 10-15% for tile and hardwood that requires cutting around corners and diagonal patterns. Our calculator's waste factor field adds this buffer automatically when estimating material needed and cost.

    How do I calculate square feet for painting a wall?

    Multiply the wall's height by its width to get the total wall area, then subtract the area of any doors and windows since they won't be painted. Use the Wall Minus Window shape in this calculator: enter the wall's height and width, then the height, width and count of any openings, and it will subtract them automatically to give you the true paintable area.

    How do I calculate the square footage of an irregular or curved space?

    Break the space into the closest standard shapes it resembles — rectangles, triangles, circles, or trapezoids — measure each section, calculate their areas individually, and add them together for the total. For a rounded reading nook or bay window, the Circle or Ellipse shapes usually approximate curved sections closely enough for material-ordering purposes. Use the project tray to add each section and see a running total.

    Does square footage include garages, porches, or unfinished basements?

    In most real estate listings, only finished, heated, and enclosed living space counts toward a home's official square footage. Garages, unfinished basements, porches, and detached structures are typically excluded and, if listed at all, shown separately as "additional" square footage. Standards vary by region and appraiser, so always check local guidelines such as ANSI Z765 for residential measurement in the US.

    What tools do I need to measure a room for square footage?

    A standard tape measure (25 feet or longer) works for most rooms, while a laser distance measurer speeds up larger spaces and reduces reading errors. You'll also want a notepad or your phone to sketch the room's outline and jot down each measurement as you go, especially for rooms with alcoves or angled walls.

    Why does my calculated square footage not match my home's listed square footage?

    Listed home square footage usually includes wall thickness, hallways, and closets and follows a specific measurement standard, while a single room measurement only covers the interior floor space of that one room. Small gaps also come from rounding, from measuring to the baseboard versus the drywall, and from whether built-in fixtures like fireplaces are subtracted.