How to Figure Square Footage
Square footage (sq ft) is a measurement of area used primarily in the United States. It tells you how much two-dimensional space is inside a boundary. One square foot equals the area of a square with sides of 1 foot (12 inches) each.
Rectangle/Square
Circle
Triangle
Trapezoid
Ellipse (Oval)
Annulus (Ring)
How to Measure Square Footage of a Room
Measure the length
Use a tape measure along the longest wall. Note the measurement in feet and inches.
Measure the width
Measure perpendicular to the length. For accuracy, measure at multiple points.
Multiply length × width
Convert inches to decimals first (e.g., 12'6" = 12.5 ft), then multiply.
Measuring L-Shaped & Irregular Rooms
Divide into rectangles
Break the L-shape into two or more rectangular sections (A and B).
Measure each section
Get the length and width of each rectangle separately.
Calculate and add
Calculate area of each section, then add them together for total square footage.
Formula: Total = (L₁ × W₁) + (L₂ × W₂) + ...
Acre to Square Footage Conversion
One of the most common conversions is acre to square footage. One acre equals 43,560 square feet. This is roughly the size of a football field (without end zones). Here's a quick reference for converting acres to square footage:
| Acres | Square Footage | Approximate Size |
|---|---|---|
| 1/4 acre | 10,890 sq ft | Large residential lot |
| 1/2 acre | 21,780 sq ft | Half football field |
| 1 acre | 43,560 sq ft | Football field (90%) |
| 2 acres | 87,120 sq ft | 2 football fields |
| 5 acres | 217,800 sq ft | Small farm |
| 10 acres | 435,600 sq ft | 10 football fields |
Quick Formula: To convert acres to square feet, multiply by 43,560. To convert square feet to acres, divide by 43,560.
Common Unit Conversions
| From | To | Multiply by |
|---|---|---|
| Square Feet | Square Meters | 0.0929 |
| Square Meters | Square Feet | 10.764 |
| Square Feet | Square Yards | 0.1111 (÷ 9) |
| Square Feet | Square Inches | 144 |
| Square Feet | Acres | 0.0000229 (÷ 43,560) |
Square Footage by Application
Flooring & Carpet
Calculate room area and add 10-15% for waste and cuts. For diagonal patterns, add 15-20%.
Paint Coverage
Measure wall height × perimeter. Subtract door/window areas. One gallon covers ~350-400 sq ft.
Landscaping & Mulch
Calculate bed area, then determine cubic yards needed. 1 cu yd covers ~100 sq ft at 3" depth.
Roofing
Measure footprint and factor in slope. Roofing is sold in "squares" (100 sq ft each).
Real Estate
Livable space typically excludes garages, unfinished basements, and porches. Price per sq ft helps compare homes.
HVAC Sizing
General rule: 20 BTU per sq ft. A 1,500 sq ft home needs ~30,000 BTU. Climate and insulation affect this.
Average Square Footage of a House
The average square footage of a house in the United States varies by region and home type. Here's what to expect:
Small Home
Under 1,500 sq ft
Medium Home
1,500–2,500 sq ft
US Average
~2,300 sq ft
Large Home
2,500–4,000+ sq ft
Average Square Footage of a Bedroom & Other Rooms
| Room Type | Average Square Footage | Typical Dimensions |
|---|---|---|
| Master Bedroom | 200-300 sq ft | 14×14 to 17×17 ft |
| Average Bedroom | 120-150 sq ft | 10×12 to 12×12 ft |
| Living Room | 200-400 sq ft | 12×18 to 20×20 ft |
| Kitchen | 100-200 sq ft | 10×10 to 12×16 ft |
| Bathroom | 40-100 sq ft | 5×8 to 10×10 ft |
| 2 Car Garage | 400-600 sq ft | 20×20 to 24×24 ft |
| 1 Car Garage | 200-280 sq ft | 10×20 to 14×20 ft |
| 3 Car Garage | 600-900 sq ft | 30×20 to 36×24 ft |
Pro Tip: Always Add Extra
When ordering materials, always add extra for waste and mistakes: Flooring: 10-15%, Tiles: 10-20% (more for diagonal patterns), Paint: round up to next gallon. It's better to have leftover material for future repairs than to run short mid-project.