Square Footage
Calculate square footage for a room, floor, or whole house from length and width measurements.
Formula
Area = Length × Width (for rectangles)
Multiply length by width for rectangles. For circles use π × r². For triangles use 0.5 × base × height. Add multiple areas together for total.
Worked Examples
Example 1: Living Room
Problem:Calculate square footage of a 20 ft × 15 ft living room.
Solution:Length = 20 feet Width = 15 feet Area = Length × Width Area = 20 × 15 = 300 square feet For flooring (with 10% waste): 300 × 1.10 = 330 sq ft Carpet (square yards): 300 ÷ 9 = 33.3 square yards
Result:300 square feet (33.3 sq yds)
Example 2: Multiple Rooms
Problem:Calculate total square footage: bedroom 12×10, bathroom 8×6, closet 4×3.
Solution:Bedroom: 12 × 10 = 120 sq ft Bathroom: 8 × 6 = 48 sq ft Closet: 4 × 3 = 12 sq ft Total = 120 + 48 + 12 = 180 square feet
Result:180 total square feet
Example 3: Circular Patio
Problem:Calculate square footage of a patio with 12-foot radius.
Solution:Radius = 12 feet Area = π × r² Area = 3.14159 × 12² Area = 3.14159 × 144 Area = 452.4 square feet For pavers (with 15% waste): 452.4 × 1.15 = 520 sq ft
Result:452 square feet circular patio
Frequently Asked Questions
How do I calculate square footage?
For a rectangle, multiply length × width. Example: 12 ft × 15 ft = 180 square feet. For irregular shapes, break into rectangles and add together. For circles: π × radius². Include closets and alcoves. Exclude stairs, fireplaces, and non-livable spaces.
How many square feet in a 10×10 room?
10 feet × 10 feet = 100 square feet. This is a common small bedroom or office size. For flooring/carpet: add 5-10% for waste. For paint: calculate wall area (perimeter × height), not floor area.
What is the difference between square feet and square yards?
1 square yard = 9 square feet (3 ft × 3 ft). Carpet is sold by square yards. Flooring and most construction by square feet. To convert: Square yards = Square feet ÷ 9. Example: 180 sq ft = 20 sq yds.
How do I measure square footage of a house?
Measure exterior dimensions or each room individually. Include: All finished living spaces, closets, hallways. Exclude: Garage, unfinished basement, attic (unless finished), porches, decks. For multi-story: measure each level. Break irregular shapes into rectangles. Professional appraisers may have different standards.
How many square feet is an acre?
1 acre = 43,560 square feet. Roughly 208.7 ft × 208.7 ft square. Common lot sizes: 1/4 acre = 10,890 sq ft (good size suburban lot). 1/2 acre = 21,780 sq ft. 1 acre is about the size of a football field without end zones.
Should I include closets in square footage?
Yes - closets count as livable space. Include in room measurements or measure separately and add. Don't include: Mechanical closets, unfinished storage, unconditioned spaces. Real estate square footage includes all finished, climate-controlled areas with minimum ceiling height (usually 7 feet).
Why do exterior measurements give a bigger total than adding up the rooms?
Exterior dimensions enclose the wall assemblies themselves, while measuring room by room captures only the finished interior floor. The gap is roughly the wall thickness multiplied by the perimeter, so a house wrapped in six-inch exterior walls plus interior partitions can measure several percent larger from outside. Appraisers normally record gross exterior area; flooring installers need the interior figure, so always state which convention a number came from.
When do I need wall area instead of floor area?
Paint, wallpaper and wainscoting are estimated from vertical surface, not the footprint. Multiply the room perimeter by the ceiling height, then subtract door and window openings. A 12 by 15 foot room with 8-foot ceilings has a perimeter of 54 feet, giving 432 square feet of wall against only 180 square feet of floor. Ceiling paint is the one coating that uses the floor figure.
How do I handle an L-shaped room or a bay window?
Split the outline into rectangles that meet along shared edges, compute each and sum them; or enclose the whole shape in one large rectangle and subtract the missing corner. A bay window projects as a shallow trapezoid, which is a rectangle plus two triangles. Sketch the plan and label every dimension first, because the commonest error is double-counting the strip where two pieces overlap.
What does a waste factor add to a material order?
A waste factor is a percentage added to the measured area to cover cuts, breakage and pattern matching. Multiply the area by one plus the factor: 240 square feet at 15 percent becomes 240 × 1.15 = 276 square feet. Straight-lay planks in a plain rectangle need the least; diagonal layouts, herringbone and patterned tile need more, and stone slabs need extra for colour matching across pieces.
Background & Theory
Square footage is the fundamental measurement for flooring, painting, construction, and real estate. Understanding how to calculate and apply it ensures accurate material estimates and project planning.
Basic Formulas:
Rectangle/Square:
Area = Length × Width
Circle:
Area = π × r² (radius squared)
Or: Area = π × (diameter/2)²
Triangle:
Area = 0.5 × base × height
Irregular Shapes:
Break into simple shapes, calculate each, add together
Conversions:
Square Feet to Square Yards:
Square Yards = Square Feet ÷ 9
Square Feet to Square Meters:
Square Meters = Square Feet ÷ 10.764
Square Feet to Acres:
Acres = Square Feet ÷ 43,560
Common Room Sizes:
| Room | Typical Size |
|---|---|
| Small bedroom | 100-150 sq ft |
| Master bedroom | 200-350 sq ft |
| Living room | 200-400 sq ft |
| Kitchen | 150-300 sq ft |
| Bathroom | 40-100 sq ft |
| 2-car garage | 400-600 sq ft |
Material Coverage per Square Foot:
Flooring: Order area + 10% waste
Carpet: Convert to sq yds, add 10%
Tile: Add 10-15% for cuts
Paint: 350-400 sq ft per gallon
Concrete (4"): 81 sq ft per cubic yard
What Counts in Home Square Footage:
✓ Finished living spaces
✓ Bedrooms, bathrooms
✓ Kitchens, dining rooms
✓ Closets, hallways
✓ Finished basements
✓ Areas with 7+ ft ceilings
✗ Garages
✗ Unfinished basements/attics
✗ Porches, decks, patios
✗ Areas under 5 ft ceiling height
Measurement Tips:
- Measure along walls, not diagonal
- Round to nearest inch for accuracy
- Sketch floor plan with dimensions
- Double-check measurements
- Use laser measure for large spaces
- Account for odd angles and niches