Square Footage Calculator

A 12 ft by 10 ft bedroom is 120 square feet - just multiply length by width. But most real projects are not one tidy rectangle: an L-shaped living room, a round patio, a backyard you want to sod, or a whole floor you are re-tiling. This square footage calculator lets you add as many areas as you need - rectangles, triangles and circles - in feet or inches, then gives you the total in square feet, square yards, square meters and acres, plus the material cost if you enter a price per square foot. It is the fast way to turn a tape-measure session into the exact number you put on an order form.

How to calculate square footage

Square footage is simply area, and area depends on the shape. The three formulas this calculator uses cover almost every real-world space:

Always convert every dimension to the same unit first. If you measured in inches, divide by 12 to get feet (so 30 in = 2.5 ft), or switch the area's units to inches and the calculator does it for you. To find the square footage of a whole room or lot, split it into these simple shapes, calculate each, and add them up.

A worked example

Suppose you are buying laminate for an open living-dining area. The main space is a 15 ft × 18 ft rectangle = 270 sq ft. A dining nook adds a 9 ft × 8 ft rectangle = 72 sq ft. A small triangular bay with a 6 ft base and 4 ft depth adds 0.5 × 6 × 4 = 12 sq ft. The total is 270 + 72 + 12 = 354 square feet. At a laminate price of $3.20 per sq ft, the material is 354 × $3.20 = $1,132.80. Add a 10% waste factor and you should actually buy about 389 sq ft (cost about $1,246), because every job loses material to cuts and trimming.

How to measure and use this calculator

You only need a tape measure (or a laser measure) and a few minutes:

1. Sketch the space and break it into rectangles, triangles, and circles. Mark each section so you know which measurement goes where.
2. Measure each section at the widest points. For rectangles record length and width; for triangles the base and the perpendicular height; for circles the diameter (straight across the middle).
3. Pick the shape and units for the first area, then type the dimensions. Switch to inches if your numbers include partial feet.
4. Add another area for each additional section. The calculator keeps a running total and shows a per-area breakdown.
5. Add price and waste (optional): enter a price per square foot and your waste factor to see both the exact cost and the realistic "order this much" cost.
6. Read the total in square feet at the top, plus the conversions to square yards, square meters and acres below it.

Converting square footage to other units

• Square yards (carpet, sod): divide square feet by 9 (a square yard is 3 ft × 3 ft).
• Acres (land, lots): divide square feet by 43,560.
• Square meters (metric quotes): multiply square feet by about 0.0929.
• Square inches: multiply square feet by 144 (12 × 12).

Who this calculator is for

• DIY homeowners buying flooring, tile, paint, or sod and needing an accurate order quantity.
• Renters and buyers checking whether a room fits a rug, a bed layout, or a sofa.
• Landscapers and gardeners sizing lawns, mulch beds, patios, and garden plots.
• Contractors and handypeople producing quick material takeoffs and quotes.
• Anyone splitting costs by area, such as shared spaces priced per square foot.

Key terms explained

• Square foot (ft²): a unit of area equal to a 1 ft × 1 ft square. It measures flat surfaces - floors, walls, lots.
• Square yard (yd²): 9 square feet. Carpet and sod are often sold and priced per square yard.
• Acre: 43,560 square feet, used for land and large lots.
• Cubic yard: a unit of volume (27 cubic feet), used for materials with depth like concrete or mulch - not the same as square footage. Convert area plus a thickness with the Cubic Yard Calculator.
• Waste factor: the extra percentage you buy to cover cuts, breakage, and mistakes; 10% is a common default, higher for complex layouts.
• Diameter and radius: for a circle, the diameter is the full width across the center; the radius is half of that. Area uses the radius.

Three quick scenarios

• Carpet for a bedroom: a 12 ft × 14 ft room is 168 sq ft, or 168 / 9 = about 18.7 square yards. Carpet is sold in widths (often 12 ft rolls), so you may pay for more than the exact figure - round up.
• Sod for a lawn: a 40 ft × 60 ft backyard is 2,400 sq ft (0.055 acres). Sod is usually priced per square foot or per pallet (about 450 sq ft each), so 2,400 sq ft is roughly 6 pallets with waste.
• A round patio: a 14 ft diameter circular patio has a 7 ft radius, so area = pi × 7² = about 154 sq ft of pavers - then add a waste factor because circular cuts produce more offcuts.

Factors that change the result

• Measurement accuracy: the biggest source of error. A few inches off on a long wall adds up over a large floor.
• Alcoves and bump-outs: closets, bays, and nooks are easy to miss; add each as its own area.
• Excluded areas: built-in cabinets, islands, or fixtures you are not covering should be subtracted (add them as a separate calculation and deduct).
• Layout and pattern: diagonal flooring, large-format tile, and patterns increase waste, so raise the waste factor.
• Units: mixing feet and inches without converting is the classic mistake - always normalize first.

Tips for an accurate order

• Always order about 10% extra. It covers cuts, breakage, and future repairs from the same dye lot or batch.
• Measure twice. Re-check the longest dimensions; small errors scale with area.
• Round up to the nearest box, roll, or pallet - you rarely buy partial units.
• Keep leftovers for patches; a replacement bought later may not match.
• Check the supplier's unit (sq ft, sq yd, box coverage) before comparing prices.

Square footage by room and home: typical sizes

It helps to have a sense of normal sizes so an unusual measurement stands out as a likely mistake. In a typical U.S. home, a bedroom runs roughly 120-200 sq ft, a primary bedroom 200-350 sq ft, a standard bathroom 40-70 sq ft, a kitchen 150-250 sq ft, and a two-car garage about 400-600 sq ft. Whole homes commonly land between 1,500 and 2,500 sq ft of finished living space. If you calculate a "bedroom" at 600 sq ft or a whole house at 400 sq ft, recheck your units - that is almost always a feet-versus-inches slip or a missing area. These ranges are also useful when you only have a floor plan: estimate each room, sum them, and you have a working figure before you ever pick up a tape measure.

Subtracting areas you are not covering

Sometimes the space you measure is not the space you are buying material for. A kitchen island, a built-in cabinet run, a fireplace hearth, or a staircase opening sits inside the room outline but does not need flooring. The reliable way to handle this is to calculate the full room area first, then calculate each excluded shape separately and subtract it from the total. For example, a 14 ft × 16 ft kitchen is 224 sq ft, but a 4 ft × 8 ft island footprint (32 sq ft) you are tiling around drops the floor you actually cover to 192 sq ft. The same logic applies in reverse for closets and alcoves you do need to cover: add each as its own area. A quick sketch with every add and subtract labeled prevents the two most common ordering errors - paying for material you will never lay, or coming up short because a nook was missed.

Square footage for paint: floors vs. walls

Square footage is not only a floor measurement. For paint you need wall area, which is the perimeter of the room multiplied by the ceiling height, minus doors and windows. A 12 ft × 12 ft room with 8 ft ceilings has a perimeter of 48 ft, so the walls are 48 × 8 = 384 sq ft before subtracting a door (about 20 sq ft) and a window (about 15 sq ft), leaving roughly 349 sq ft to paint per coat. This calculator computes any rectangular surface - enter the perimeter as the length and the ceiling height as the width to get wall area, or measure each wall as its own rectangle. For a full paint estimate including coats and coverage per gallon, hand the total to the Paint Calculator.

Limitations and assumptions

This is a planning estimate based on the dimensions you provide:

• It calculates flat, level area. Sloped roofs, stairs, and curved walls need separate handling.
• It does not compute volume. For depth-based materials (concrete, mulch, gravel) use the Cubic Yard Calculator.
• It does not apply any official "living area" standard; advertised home square footage may differ.
• Accuracy is only as good as your measurements - measure carefully and add waste.

Related materials and tools

Once you know the square footage, a sister calculator turns it into the right material quantity:

• For depth-based volume, use the Cubic Yard Calculator.
• For slabs and footings, use the Concrete Calculator.
• For driveways and beds, use the Gravel Calculator or Mulch Calculator.
• For walls and ceilings, use the Paint Calculator.
• For floors and backsplashes, use the Tile Calculator, Flooring Calculator, or Carpet Calculator.
• For a pitched roof, use the Roofing Calculator, which accounts for slope that a flat-area figure ignores.

Sources

• National Institute of Standards and Technology (NIST) - unit conversions and definitions of area units.
• NIST Handbook 44 - Specifications, Tolerances, and Technical Requirements for Weighing and Measuring Devices (legal definitions of foot, yard, and acre).
• U.S. Census Bureau - Characteristics of New Housing (median floor area of U.S. homes).