Which tool fits the job
For a whole room, start with a planner: the room painting planner adds primer, tape, rollers and trim paint to the gallons, and the laminate floor planner and tile floor planner lay out every row to scale with the underlayment, thin-set, grout and trim. For one material, use the paint, drywall, flooring, tile, grout, thin-set, carpet or baseboard calculator.
Plan in this order
Measure each wall and the floor, subtract doors and windows, then convert to the store’s unit: gallons, sheets, boxes, square yards or pieces. A 12 × 12 ft room with 8 ft walls has 384 sq ft of wall; less a door and two windows that is 333 sq ft, so two coats at 350 sq ft per gallon take about 1.9 gallons. Buy 2.
Common buying mistakes
- Buying the exact area. Flooring comes in whole boxes: a 12 × 14 ft room is 168 sq ft, 184.8 with 10% extra, so 10 boxes of 20 sq ft. Keep a spare box for repairs.
- Forgetting the grout joint. 100 sq ft of 12 × 12 in tile with ⅛ in joints takes about 98 tiles, or 108 with 10% extra.
- Carpet by floor area. Carpet comes off a 12 ft roll, so a 12 × 14 ft room (18.7 sq yd) needs 19.3 sq yd with trimming.
- Trim by linear feet alone. A 9 × 9 ft room needs four 16 ft pieces of baseboard to avoid joints, not three.
- Too little joint compound. Plan about 1 gallon per 100 sq ft of drywall.
In a house built before 1978, test old paint for lead before you sand or scrape, and have old vinyl flooring and its adhesive tested for asbestos before you pull them up.