How to calculate square footage
For a rectangular space, multiply length × width (both in feet) to get square feet. A 12-foot × 15-foot room is 180 sq ft. If your measurements are in inches, divide by 12 first.
Rectangle: area = length × width
For irregular rooms, break the space into simple rectangles and triangles, calculate each, then add them together. Closets, bay windows, and bump-outs are usually handled as separate rectangles.
Formulas for each shape
Rectangle / Square
area = length × width
Most rooms. A 10×12 room = 120 sq ft.
Circle
area = π × r²
A 10-foot radius circle = 314 sq ft.
Triangle
area = ½ × base × height
A 10-foot base, 8-foot height triangle = 40 sq ft.
L-shape
area = (L₁×W₁) + (L₂×W₂)
Split into two rectangles, sum the areas.
Common room sizes
Typical US room sizes for reference:
| Room | Range | Typical |
|---|---|---|
| Bedroom (standard) | 120–200 sq ft | 144 sq ft (12×12) |
| Master bedroom | 200–350 sq ft | 280 sq ft (14×20) |
| Living room | 200–400 sq ft | 300 sq ft (15×20) |
| Kitchen | 100–200 sq ft | 160 sq ft (10×16) |
| Dining room | 100–200 sq ft | 150 sq ft (12×12.5) |
| Bathroom (full) | 40–100 sq ft | 80 sq ft (8×10) |
| Half bath | 18–40 sq ft | 25 sq ft (5×5) |
| Home office | 75–150 sq ft | 120 sq ft (10×12) |
| Garage (1-car) | 200–300 sq ft | 240 sq ft (12×20) |
| Garage (2-car) | 400–600 sq ft | 480 sq ft (20×24) |
How to measure a room
- Measure wall-to-wall at the baseboards — don't include the baseboard itself, and skip any built-in cabinets or fixtures.
- Use a laser measure if you have one. A 25-foot tape measure works for most rooms if you're careful to keep it taut and straight.
- Record in inches for accuracy, then convert to feet at the end. "11 feet 8 inches" is more precise than "about 12 feet."
- Handle closets separately — calculate closet floor area and add to the main room, or keep separate if closets don't need the same treatment.
- For irregular shapes, break the floor into rectangles you can measure. Add the areas. For curves, approximate with triangles or quarter-circles.
Flooring, painting, and landscaping
Flooring
Calculate room sq ft, then add 5–10% for waste (up to 15% for diagonal patterns and complex layouts). Flooring comes in full boxes — round up.
Painting
Wall area, not floor area. Perimeter × ceiling height. Subtract ~20 sq ft per door and ~15 sq ft per window. One gallon covers about 350 sq ft per coat; plan for two coats.
Landscaping / sod
Measure yard in sq ft. Sod is typically sold in pallets of 450 sq ft. For seed, check bag coverage (usually 1,000–4,000 sq ft per bag).
Unit conversion reference
| From | To | Multiply by |
|---|---|---|
| Square meters | Square feet | × 10.764 |
| Square feet | Square meters | × 0.0929 |
| Square yards | Square feet | × 9 |
| Square feet | Square yards | × 0.1111 |
| Acres | Square feet | × 43,560 |
| Square feet | Acres | ÷ 43,560 |
Cost per square foot guide
National average cost ranges for common projects (materials + installation):
| Project | Cost / sq ft | Notes |
|---|---|---|
| Interior painting | $1.50–$3.50 | Paint + labor; walls only |
| Carpet flooring | $3.50–$6.00 | Mid-grade with padding |
| Laminate flooring | $3.00–$8.00 | Including installation |
| Hardwood flooring | $8.00–$15.00 | Engineered or solid oak |
| Tile flooring | $7.00–$14.00 | Ceramic or porcelain installed |
| Vinyl / LVP | $2.50–$7.00 | Luxury vinyl plank installed |
| Drywall installation | $1.50–$3.50 | Materials + hanging + finishing |
| Landscaping (basic) | $4.00–$12.00 | Grass, mulch, simple beds |
| Concrete patio | $6.00–$12.00 | 4-inch slab, basic finish |
| Roofing (asphalt) | $3.50–$7.50 | Per sq ft of roof area |
| New home construction | $150.00–$400.00 | National average varies by region |
Costs vary by region, quality level, and contractor. Use our calculator to estimate total project cost based on your measured area.
Frequently asked questions
How do I calculate square feet of a room?
For a rectangular room, multiply the length by the width, both measured in feet. Formula: area = length × width. A 12-foot by 15-foot room is 12 × 15 = 180 square feet. Measure wall-to-wall, not including baseboards. If your measurements are in inches, divide by 12 first to convert to feet (e.g., 144 inches = 12 feet). Our square footage calculator handles unit conversions and irregular shapes automatically.
How many square feet is a 12x12 room?
A 12x12 room is 144 square feet (12 × 12 = 144). This is a common bedroom size. Related dimensions: 10×10 = 100 sq ft, 10×12 = 120 sq ft, 12×14 = 168 sq ft, 12×15 = 180 sq ft, 14×16 = 224 sq ft. For flooring purposes, add 5–10% for waste and cuts — so budget ~155 sq ft of flooring for a 12x12 room.
How do I calculate square feet from inches?
Divide inch measurements by 12 to get feet, then multiply. Example: 144 inches × 96 inches = 12 feet × 8 feet = 96 square feet. Alternatively, multiply the inches first (144 × 96 = 13,824 square inches), then divide by 144 (which is 12 × 12) to get square feet: 13,824 ÷ 144 = 96 sq ft. Our calculator handles the conversion automatically — just pick 'inches' as the unit.
How many square feet in an acre?
One acre equals 43,560 square feet. That's roughly the size of a football field minus the end zones. Common equivalents: quarter acre = 10,890 sq ft (typical suburban lot), half acre = 21,780 sq ft, 1 acre = 43,560 sq ft, 5 acres = 217,800 sq ft. An acre is about 208 feet × 208 feet (square) or 66 feet × 660 feet (the old furlong-chain measurement it comes from).
How do I calculate square footage of an odd-shaped room?
Break the room into simple rectangles and triangles, calculate each separately, then add them together. For an L-shaped room, draw the two rectangles that make up the L, calculate each, and sum. For rooms with bay windows or cutouts, calculate the main rectangle then subtract the cutout or add the bay. Our L-shape tab handles two-rectangle shapes automatically; for more complex shapes, divide into pieces and add the results.
How do I calculate sq ft for flooring?
Calculate the room's square footage, then add 10% for waste (5% for simple rooms, 15% for complex layouts with lots of cuts). For a 200 sq ft room, order 220 sq ft of flooring. Flooring comes in boxes — round up to the nearest full box. Also measure and subtract any built-in cabinets or fixtures the floor won't go under. Transition strips, underlayment, and trim are separate.
What is the square footage of a circle?
Area of a circle = π × r² (pi times radius squared). For a circular patio with a 10-foot radius: area = 3.14159 × 10² = 3.14159 × 100 = 314.16 sq ft. If you know the diameter instead of the radius, divide by 2 first (radius = diameter ÷ 2). A 20-foot diameter circle has a 10-foot radius, so the area is the same 314.16 sq ft.
How do I convert square meters to square feet?
Multiply square meters by 10.764 to get square feet. A 100 square meter apartment equals 1,076 square feet. Common conversions: 50 sq m = 538 sq ft, 75 sq m = 807 sq ft, 100 sq m = 1,076 sq ft, 150 sq m = 1,615 sq ft, 200 sq m = 2,153 sq ft. Going the other way, divide sq ft by 10.764 to get sq m (or multiply by 0.0929).
How many square feet do I need for paint?
For walls: multiply wall length by ceiling height to get wall area per wall, sum all walls, then subtract doors (20 sq ft each) and windows (15 sq ft each). For a 12×15 room with 8-foot ceilings: perimeter = 54 feet × 8 = 432 sq ft, minus 1 door and 2 windows (~50 sq ft) = 382 sq ft. One gallon covers ~350 sq ft in one coat. Budget two coats, so 2 gallons for this room.
How do I measure square footage for rent?
Landlords and real estate listings typically use 'gross' square footage — total enclosed area including interior walls, closets, and sometimes hallways. Measure wall-to-wall on the interior of exterior walls. Don't include garages, balconies, patios, or unfinished basements in the main sq ft figure (these are listed separately). For condos and apartments, the listed square footage usually excludes shared common areas.