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.

[Calculate square footage →](https://doesitaddup.com)

This article is for informational purposes only. See our disclaimer.