Quick answer
Room square footage = length × width in feet. A 12 × 10 room = 120 sq ft. Add rooms for house totals; add 5–10% waste for flooring. Use the free square footage calculator.
Room square footage calculator basics
Room sq ft = Length (ft) × Width (ft)
Measure wall-to-wall at the widest points. Convert mixed feet/inches to decimal feet (6 in = 0.5 ft). For L-shaped rooms, calculate two rectangles and add.
| Room | Size | Sq ft |
|---|---|---|
| Bedroom | 12 × 10 | 120 |
| Living room | 15 × 12 | 180 |
| Kitchen | 12 × 12 | 144 |
| Bathroom | 8 × 5 | 40 |
House square footage calculator tips
Listings typically follow ANSI Z765: finished, heated, enclosed living space only. Measure rooms (or exterior footprint for detached homes), sum floors separately for two-story homes, and exclude garages, unfinished basements, and open porches.
Example: 1,000 sq ft main + 800 sq ft upper = 1,800 sq ft home — not 2,000.
Walls, paint, flooring & tile
- Walls: width × height − openings.
- Paint: ~350–400 sq ft per gallon per coat.
- Flooring: floor area + 5–10% waste.
- Tile: +10–15% for cuts/diagonal layouts.
Countertops & cost per square foot
Countertop sections: inches × inches ÷ 144 = sq ft. Multiply by installed $/sq ft for budget ranges (often $40–$200+/sq ft depending on material).
More formulas: how to calculate square footage. Lot/acres: acres square footage guide.