Fast method (rectangular rooms)
- Measure length and width in feet.
- Multiply: sq ft = L × W
Example: 12 ft × 12 ft = 144 sq ft.
How to Calculate Square Footage of a Room Easily
How to Calculate Square Footage of a Room Easily
Square footage (sq ft) = area. It’s the baseline for estimating paint, flooring, and project costs.
Odd-shaped rooms
Split the space into rectangles/squares, compute each, then add totals.
Example: Nook (8×5) = 40; Main (18×10) = 180 → Total = 220 sq ft.
No tape? Pace it
One wide step ≈ 3 ft. Count steps in each direction, multiply by 3 to get length/width, then compute L × W.
Walls, ceilings, and trim
- Wall area: Perimeter × Height. Subtract big openings for precision.
- Ceiling: Length × Width.
- Trim (linear feet): doors, baseboards, and casings are tracked in LF, not sq ft.
Typical door = 21 sq ft (3×7). Typical window = 12 sq ft (3×4). Closets ~42 sq ft (6×7).
Paint planning (rules of thumb)
- Wall coverage ≈ 350–400 sq ft/gal/coat
- Plan **two coats** for uniform color
- Trim coverage ≈ 650–800 LF/gal
Ceiling height hack
Standard door is **7 ft**. If the top of the door sits ~1 ft below the ceiling, you likely have **8 ft** ceilings; 2–3 ft below suggests **9–10 ft**.
Common room sizes
| Room | Dimensions | Sq Ft |
|---|---|---|
| Small bedroom | 10×12 | 120 |
| Standard bedroom | 12×12 | 144 |
| Large bedroom | 12×14 | 168 |
| Dining | 14×16 | 224 |
| Living | 18×15 | 270 |
| Great room | 20×18 | 360 |
Whole-home square footage
- Sketch each floor; label rooms.
- Measure each room’s L × W; write totals on the sketch.
- Add all finished, heated spaces. Exclude garages, unfinished attics, or storage unless finished.
Modern homes often have 9–10 ft ceilings; taller walls increase paint quantities and labor time.
FAQs
Do I include trim width in wall sq ft?
For quick estimates, yes. For precision, subtract wider (≥6″) baseboards/crowns from wall height.
What if I’m matching a similar color?
Count on **two coats** anyway. One-coat marketing claims rarely produce an even, durable finish.
Why does square footage matter?
It drives material quantities, quotes, taxes, and appraisals — and helps you decide whether DIY or hire a pro based on cost per sq ft.
