Room Area Calculator
Calculate the square footage of any room shape. Supports rectangular, square, and L-shaped rooms.
Divide your L-shaped room into two rectangles (A and B) and enter each.
How to Calculate Room Area
For rectangular rooms, multiply length × width. For L-shaped rooms, stand in the corner of the L, mentally divide the space into two rectangles at the inside corner, measure each rectangle separately, and add the two areas together. Always measure at the widest points of each dimension.
Triangular rooms or alcoves are calculated as base × height ÷ 2. In practice, most triangular spaces in homes come from bay windows or oddly angled additions — for these, measuring the bounding rectangle and using a 10% waste factor is often simpler and close enough for material purchasing purposes.
Square Feet vs. Square Yards
Square feet is the standard unit for most home improvement materials in the US — flooring, tile, paint, drywall, and renovation cost estimates are all quoted in square feet. Square yards (sq ft ÷ 9) is primarily used for carpet, which is sold by the square yard at most retailers.
When buying carpet, always get your square footage first, then divide by 9 to get square yards. Add 10% for waste before converting. A 120 sq ft room needs 132 sq ft with waste, or 14.7 sq yd → order 15 square yards.
Tips for Accurate Measurements
- Measure at floor level, not at counter height — walls sometimes angle slightly near the ceiling
- Include the space under door thresholds in your measurement — flooring runs there
- Measure closets separately and add them to the room total
- For rooms with bump-outs or nooks, measure the full bounding rectangle and use a higher waste factor
- Double-check by measuring twice from different starting points
Common Room Sizes and Their Square Footage
| Room Type | Typical Dimensions | Square Footage |
|---|---|---|
| Small bathroom | 5 × 8 ft | 40 sq ft |
| Standard bathroom | 8 × 10 ft | 80 sq ft |
| Master bathroom | 10 × 12 ft | 120 sq ft |
| Small bedroom | 10 × 10 ft | 100 sq ft |
| Standard bedroom | 12 × 12 ft | 144 sq ft |
| Master bedroom | 14 × 16 ft | 224 sq ft |
| Kitchen | 10 × 12 ft | 120 sq ft |
| Open kitchen/dining | 14 × 20 ft | 280 sq ft |
| Living room (small) | 12 × 14 ft | 168 sq ft |
| Living room (standard) | 15 × 20 ft | 300 sq ft |
How Square Footage Affects Material Quantities
Once you have your room's square footage, calculating materials is straightforward. Always add a waste factor before purchasing — 10% for most flooring types, 15–20% for diagonal or patterned layouts, and 10% for paint (to account for doors, windows, and a second coat on accent walls).
| Material | Coverage Per Unit | Waste Factor |
|---|---|---|
| Paint (1 gallon) | ~350 sq ft (1 coat) | Add 10% |
| Flooring (box) | Varies by product | Add 10–15% |
| Tile (12×12 in) | 1 sq ft per tile | Add 10–20% |
| Carpet | Sold per sq yd (= 9 sq ft) | Add 10% |
| Drywall (4×8 sheet) | 32 sq ft per sheet | Add 10% |
Frequently Asked Questions
How do I calculate the square footage of a room?
Multiply the room length by the room width in feet. A 12 ft x 10 ft room = 120 square feet. For L-shaped rooms, divide into two rectangles, calculate each, and add them together.
How do I measure an L-shaped room?
Stand in the inside corner of the L and mentally divide the space into two rectangles. Measure each rectangle separately — length x width — then add the two areas together for the total square footage.
Should I include closets in my room area measurement?
Yes, always include closets when calculating flooring or carpet. Measure the closet separately and add it to the room total. A standard reach-in closet adds 8–15 sq ft; a walk-in closet can add 25–80 sq ft.
What is the difference between square feet and square yards?
There are 9 square feet in one square yard. Divide square feet by 9 to get square yards. Most flooring and tile is sold by the square foot; carpet is sold by the square yard.
How much should I add for waste when ordering flooring?
Add 10% waste for standard straight-lay flooring, 15% for diagonal lay, and 15–20% for patterned tile or hardwood with significant cutting waste.