Room Paint Calculator – Walls, Ceiling & Trim Paint Separately

The Room Paint Calculator works out paint for a whole room with separate amounts for the three paints most rooms use: wall paint, ceiling paint and trim (baseboard) paint.

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Room Paint Calculator

Paint for a whole room from its dimensions — separate amounts for walls, ceiling and trim.

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Other calculators for related paint calculations.

Wall Paint CalculatorPaint for one wall or several walls, minus doors and windows, in gallons and litres.Open Calculator Interior Painting Cost CalculatorEstimate interior painting cost for a room or whole house — walls, ceilings, paint and labour.Open Calculator Trim & Door Paint CalculatorPaint for doors, baseboards, window and door trim, crown moulding and cabinets — in quarts or gallons.Open Calculator Bathroom Painting Cost CalculatorHow much paint a bathroom needs and what painting it costs — walls, ceiling, minus tiled areas, doors and windows.Open Calculator Car Paint CalculatorHow much automotive base coat, clear coat and primer to buy for a full respray by vehicle size, or from the area you are painting.Open Calculator Painting Cost CalculatorEstimate a painting job: paint cost, labour by area or by hours, prep and supplies.Open Calculator
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Similar Calculator:  Trim & Door Paint Calculator – Baseboards, Doors, Crown & Cabinets

Walls are calculated from the perimeter × height minus doors and windows; the ceiling from length × width; and trim from the perimeter × the baseboard face height. Wall and ceiling paint appear in gallons, trim paint in quarts.

Formula

  • Wall paint: (2(L + W) × H − 21 ft² × doors − 15 ft² × windows) × coats ÷ wall coverage
  • Ceiling paint: L × W × coats ÷ ceiling coverage
  • Trim paint: 2(L + W) × trim height × coats ÷ wall coverage

How the Calculation Works

Step 1: Calculate the three surfaces separately.

Step 2: Multiply each by the number of coats.

Step 3: Divide by the coverage for each paint.

Example Calculation

Given: 14 × 12 ft room, 8 ft walls, 1 door, 2 windows, 2 coats, 350 ft²/gal for walls and ceiling, 4 in baseboard

  • Walls = 416 − 21 − 30 = 365 ft² → 365 × 2 ÷ 350 ≈ 2.09 gal
  • Ceiling = 168 ft² → 168 × 2 ÷ 350 = 0.96 gal
  • Trim = 52 ft × 0.333 ft = 17.3 ft² → ≈ 0.10 gal ≈ 0.4 qt

Shopping list: 3 gallons (or 2 gallons + 1 quart) of wall paint, 1 gallon of ceiling paint, 1 quart of trim paint.

Why Separate the Paints?

  • Ceilings are often painted with a flat ceiling paint.
  • Trim usually gets a more durable semi-gloss or gloss.
  • Walls may be a different color and sheen from both.

Material Estimation Notes

  • The trim estimate covers baseboards only; door and window casings and doors are in the Trim & Door Paint Calculator.
  • Buy whole cans and keep leftovers for touch-ups.

Frequently Asked Questions

How much paint do I need for a room?

Calculate walls, ceiling and trim separately; the example 14 × 12 room needs about 2.1 gallons for the walls.

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How much ceiling paint do I need?

Ceiling area × coats ÷ coverage; a 14 × 12 ceiling needs about a gallon for two coats.

How much paint for baseboards?

Usually a quart is plenty for a single room.

Should the ceiling be painted first?

Many painters work top-down: ceiling, then walls, then trim.

Does this include the door?

No — the door is subtracted from the walls; paint it using the Trim & Door Paint Calculator.

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