Loading…
Gallons or liters of paint for a room, coats and openings counted.
🎨 Coverage assumes smooth primed walls at the typical 10 m²/L. Textured surfaces, bare drywall, or dramatic color changes eat 20-40% more. Buy one can from the same batch — batch tinting varies.
One liter covers about 10 m² per coat on smooth primed walls; a US gallon covers ≈37 m² (400 ft²). Textured plaster, bare drywall, or bold color changes can demand 20-40% more.
Standard doors subtract 1.85 m² and windows 1.4 m² each. Trimming and door frames consume some of that saving, so the deduction is approximate — which is why we keep a margin.
Most paints specify two coats for true color and washability; one-coat claims need premium paint over a close-matching base. The calculator multiplies by coats automatically.
Batch matters: mix cans from different production lots can differ visibly in tint. Buy the full quantity at once, keep the receipt, and unopened cans usually return fine.
The Paint Calculator lets you figure out paint calculatorinstantly, without reaching for a spreadsheet or doing the math by hand. Whether you're planning a budget, checking a loan, or working through homework, the tool applies the correct formula behind the scenes and shows the result the moment you enter your numbers.
Unlike a static chart or table, this calculator adapts to your exact inputs. You can adjust any value and see the outcome update in real time, which makes it easy to compare scenarios — for example, "what if the rate were 1% lower?" or "what if I paid an extra $50 a month?"
Common uses: people reach for this tool when they need to find a how many gallons paint 12x12 room, paint coverage per litre calculator, two coats paint quantity estimator, or subtract door window wall area paint.
Browser-based tools like this one have a few real advantages over installed software or manual methods:
The Paint Calculator is based on the following formula:
wall area = 2 × (L + W) × H net area = wall area − (doors × 21 + windows × 15) gallons = net area × coats ÷ 350 (1 US gallon covers ≈ 350-400 ft² per coat; door ≈ 21 ft², window ≈ 15 ft²)
Variables: L, W = Room length and width (ft) H = Wall height (ft) wall area = Total wall surface (ft²) net area = Wall area after subtracting doors and windows (ft²) coats = Number of coats of paint gallons = Paint to buy (US gallons) 350 = Coverage of one gallon per coat, typical range 350-400 ft²
Paint volume is just the paintable surface area times the number of coats, divided by the coverage of one gallon (about 350-400 ft²). Doors and windows are subtracted first, and rounding up adds the waste margin for spills, touch-ups, and porous walls.
Worked example: Step 1: Room 14 ft × 12 ft with 8 ft ceilings: wall area = 2 × (14 + 12) × 8 = 416 ft². Step 2: One door (21 ft²) and two windows (2 × 15 = 30 ft²): net area = 416 − 51 = 365 ft². Step 3: Two coats: 365 × 2 = 730 ft² of coverage needed. Step 4: gallons = 730 ÷ 350 ≈ 2.1. Result: about 2.1 gallons for two coats — buy 3 gallons for a safe margin (2 may just cover if your paint reaches 400 ft²/gallon).
More tools you might find useful