How do you calculate square footage?

For a rectangle or square, multiply length × width (both in feet). For example, a 12×15 foot room = 180 square feet. If your measurements are in inches, multiply length × width in inches, then divide by 144 to get square feet. For irregular shapes, break the area into rectangles, calculate each one, and add them together.

How many square feet is a 10x10 room?

A 10×10 room is 100 square feet. To calculate: 10 feet × 10 feet = 100 sq ft. This is a common small bedroom size. For flooring, you'd need about 110 sq ft of material (adding 10% for waste and cuts).

How do I calculate square footage for flooring?

Measure each room's length and width in feet, multiply them together, then add all rooms. Add 10% waste for standard installations or 15% for diagonal patterns. For example: Living room (15×20 = 300) + Bedroom (12×14 = 168) = 468 sq ft. With 10% waste: 468 × 1.10 = 515 sq ft of flooring needed.

How do you calculate square footage of an irregular shape?

Break the irregular shape into simple rectangles, triangles, or circles. Calculate each section's area separately, then add them all together. For L-shaped rooms, split into two rectangles. For rooms with bay windows or bump-outs, add the bump-out area to the main room. For curved areas, use the circle formula: π × radius².

How many square feet in an acre?

One acre equals 43,560 square feet. A half acre is 21,780 sq ft, and a quarter acre is 10,890 sq ft. For reference, a standard American football field (not including end zones) is about 48,000 sq ft, slightly larger than an acre. To convert square feet to acres, divide by 43,560.

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How to Calculate Square Footage: Complete Guide

Square footage is the most common measurement in construction, real estate, and home improvement. Whether you're ordering flooring, estimating paint, or listing a property, accurate square footage is essential.

Basic Square Footage Formulas

Shape	Formula	Example
Rectangle / Square	Length × Width	12 ft × 15 ft = 180 sq ft
Circle	π × radius²	π × 5² = 78.5 sq ft
Triangle	½ × base × height	½ × 10 × 8 = 40 sq ft
Trapezoid	½ × (a + b) × height	½ × (8+12) × 6 = 60 sq ft

Tip: If your measurements are in inches, calculate the area in square inches, then divide by 144 to convert to square feet (12 × 12 = 144).

Common Room Sizes (Square Feet)

Room Type	Typical Size	Square Feet
Small Bedroom	10 × 10	100 sq ft
Standard Bedroom	12 × 12	144 sq ft
Master Bedroom	14 × 16	224 sq ft
Living Room	15 × 20	300 sq ft
Kitchen	12 × 16	192 sq ft
Full Bathroom	8 × 10	80 sq ft
Half Bathroom	5 × 8	40 sq ft
1-Car Garage	12 × 22	264 sq ft
2-Car Garage	22 × 22	484 sq ft
Standard Deck	12 × 16	192 sq ft

Unit Conversions

From	To	Multiply By
Square Feet	Square Yards	÷ 9
Square Feet	Square Meters	× 0.0929
Square Feet	Acres	÷ 43,560
Square Meters	Square Feet	× 10.764
Square Yards	Square Feet	× 9
Acres	Square Feet	× 43,560

How to Measure Irregular Rooms

Most rooms aren't perfect rectangles. Here's how to handle common situations:

L-Shaped rooms: Split into two rectangles. Measure each one separately and add the areas together.
Rooms with alcoves or bump-outs: Measure the main rectangle, then add the alcove area.
Rooms with bay windows: Approximate the bay as a trapezoid and add to the main room area.
Rounded walls: Approximate as a half-circle (½ × π × r²) and add to the rectangular portion.
Angled walls: Create a right triangle from the angle. Calculate the triangle area and add or subtract from the rectangle.

Square Footage for Materials Estimating

Material	Coverage per Unit	Waste Factor
Interior paint (1 gal)	350–400 sq ft	+10%
Exterior paint (1 gal)	250–350 sq ft	+15%
Hardwood flooring	Per sq ft purchased	+10% (straight) / +15% (diagonal)
Ceramic tile	Per sq ft purchased	+10–15%
Carpet (sold by sq yd)	÷ 9 for sq yards	+10%
Drywall (4×8 sheet)	32 sq ft per sheet	+10%
Insulation (R-13 batt)	Per sq ft	+5%
Roofing (1 square)	100 sq ft	+10–15%
Sod (per pallet)	450–500 sq ft	+5%
Mulch (1 cu yd, 3" deep)	108 sq ft	+10%

5 Square Footage Mistakes That Cost Money

Forgetting to subtract openings. For drywall and paint, subtract doors (~21 sq ft each) and windows (~12 sq ft each). For flooring, don't subtract — you still need to cut boards to fit around them.
Mixing up feet and inches. A "12 × 14" room means 12 feet × 14 feet = 168 sq ft. If you accidentally use inches (12" × 14" = 168 sq in = 1.17 sq ft), you'll be off by a factor of 144.
Not accounting for waste. Every cut generates waste. Tile cuts are especially wasteful at borders and around obstacles. Always add your waste factor before ordering.
Using outer walls instead of inner walls. For flooring, measure from wall to wall on the inside. Measuring from the outside adds the wall thickness (typically 4.5"–6") on each side.
Rounding down instead of up. Always round up to the next full unit when ordering materials. 147 sq ft of tile with 10% waste = 162 sq ft. If tiles come in boxes of 25 sq ft, order 7 boxes (175 sq ft), not 6.

Square Footage in Real Estate

How square footage is measured in real estate differs from construction measurements. Understanding the rules prevents disputes and ensures accurate listings.

What Counts as "Living Space"?

Included: All heated/cooled rooms with finished floors, walls, and ceilings. Bedrooms, living rooms, kitchens, bathrooms, hallways, closets, and laundry rooms.
Usually excluded: Garages, unfinished basements, unfinished attics, covered porches, screened rooms, and detached structures.
Varies by market: Finished basements are sometimes counted at 50–100% depending on local MLS rules. Below-grade space is often listed separately.

Average Home Sizes (USA)

Home Type	Average Sq Ft	Price/Sq Ft (2026)
Studio apartment	400–600	$200–$400
1-bedroom apartment	600–800	$175–$350
Small house (2BR)	800–1,200	$150–$300
Average house (3BR)	1,500–2,000	$150–$275
Large house (4BR+)	2,500–3,500	$140–$250
New construction avg	2,200–2,500	$175–$325

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