Square Footage Calculator: Floor Plans, Paint, Flooring, and More
Square footage is simple for rectangular rooms: length × width. Real homes have irregular rooms, closets, bay windows, and alcoves that require a bit more work. Getting this right saves significant money on flooring, paint, and tile.
Basic Calculation
For a rectangle: length × width = square footage
A 12×14 room: 12 × 14 = 168 sq ft
Irregular Rooms
Break the room into rectangles. Calculate each separately. Add them together.
L-shaped room: draw two rectangles, calculate each, sum them.
Room with a closet: include the closet floor area if flooring; exclude it if painting walls.
Material Estimates
Paint:
Wall square footage = perimeter × ceiling height, minus doors (~20 sq ft each) and windows (~15 sq ft each).
One gallon covers ~350–400 sq ft per coat. Most rooms need 2 coats.
A 12×14 room with 8-ft ceilings: (12+14+12+14) × 8 = 416 sq ft walls, minus 2 doors (40 sq ft) and 2 windows (30 sq ft) = 346 sq ft. At 2 coats: ~2 gallons.
Flooring:
Add 10% overage for waste and cuts on straight patterns.
Add 15% for diagonal installation (more cuts, more waste).
Add 5% extra for future repairs (buy extra and store it — matching discontinued flooring later is difficult).
Tile:
Same as flooring — 10% overage standard, more for complex patterns.
Grout lines affect tile count slightly but not enough to matter for buying purposes.
Carpet:
Carpet is sold by the yard (1 yard = 9 sq ft). Divide sq ft by 9 to get sq yds. Add 10% overage.
Important: carpet comes in fixed widths (usually 12 ft). How you orient rooms in the width affects waste significantly.
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Frequently Asked Questions
How much paint do I need for a 12×14 room with 8-foot ceilings?
Calculate wall square footage using the perimeter formula: (12+14+12+14) × 8 = 416 sq ft. Subtract doors (20 sq ft each) and windows (15 sq ft each)—for example, 2 doors and 2 windows = 70 sq ft total, leaving 346 sq ft. Divide by coverage (350–400 sq ft per gallon) and multiply by 2 coats: you'll need approximately 2 gallons.
Should I include closets when calculating square footage for flooring versus painting?
Yes, but it depends on the project. For flooring, include the closet floor area in your total square footage since you're covering that floor. For painting walls, exclude the closet—you're only painting the walls of the main room. This distinction directly affects how much material you buy.
Why should I add extra flooring material beyond the square footage I calculated?
Add 10% overage for straight patterns and 15% for diagonal installation to account for cuts and waste during installation. Additionally, buy an extra 5% and store it for future repairs, since matching discontinued flooring styles later is extremely difficult. This prevents costly shortages and future headaches.
How do I calculate square footage for an L-shaped or irregular room?
Break the irregular shape into separate rectangles, calculate the length × width for each, then add them together. For example, an L-shaped room can be divided into two rectangles—calculate each one's square footage separately and sum them for the total room area. This method works for rooms with closets, bay windows, and alcoves too.
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