Room Makeover Math: Estimating Paint and Flooring Like a Pro
Measure a room once and work out exactly how many gallons of paint and boxes of flooring to buy, with waste allowances and budgeting tips.
Paint and flooring are the two biggest purchases in most room makeovers. Both are sold in fixed units, gallons and boxes, so a little math up front avoids extra store trips and leftover stock you cannot return.
Measure the room once
You need three measurements: the length and width of the floor and the height of the walls. Measure at floor level from wall to wall, rounding up to the nearest half foot. Note the number of doors and windows.
Example: a bedroom 12 ft × 14 ft with 8 ft ceilings, one door and two windows.
Paint: wall area minus openings
- Perimeter: 12 + 14 + 12 + 14 = 52 ft.
- Wall area: 52 × 8 = 416 ft².
- Subtract openings: a standard door is about 21 ft² and a window about 15 ft², so 416 − 21 − 30 = 365 ft².
- Two coats: 730 ft² of coverage needed.
- At 350 ft² per gallon: 730 ÷ 350 = 2.1 gallons.
Buy 2 gallons plus a quart, or 3 gallons if you want leftovers for touch-ups. The ceiling, 12 × 14 = 168 ft², needs about one gallon of ceiling paint for two coats.
Paint tips
- Coverage drops on textured or porous surfaces; use 300 ft² per gallon for fresh drywall or rough plaster.
- Prime when covering dark colors, stains or new drywall.
- Trim and doors usually take a semi-gloss finish, about one quart for an average room.
Flooring: area plus waste
- Floor area: 12 × 14 = 168 ft².
- Add waste: 10% for a standard straight layout gives 184.8 ft².
- Divide by box coverage: at 22 ft² per box, 184.8 ÷ 22 = 8.4, so buy 9 boxes.
Increase the waste allowance to 15% for diagonal tile and up to 20% for herringbone. Include closets if the flooring continues into them, and remember transition strips at doorways.
Budgeting the project
| Item | Quantity | Typical cost |
|---|---|---|
| Wall paint | 2–3 gallons | $35–80 per gallon |
| Ceiling paint | 1 gallon | $25–50 |
| Laminate or vinyl plank | ~185 ft² | $2–5 per ft² |
| Underlayment, trim, supplies | — | $100–300 |
Prices vary by brand and region; use these as rough planning ranges and get current prices from local stores.
Order of work
Paint before installing new flooring, so drips land on the old floor. Paint the ceiling first, then walls, then trim. Let paint cure for a day before laying flooring and fitting baseboards.
The paint, flooring and square footage calculators do all of this arithmetic for you, including cost.