DIY Paint Calculator
DIY Paint Calculator — Easy Paint Estimate for Walls & Ceilings
Use this guide and the free paint calculator to find out how many litres of paint you need and how much it will cost. Simple steps for home projects, room by room.
Why use a paint calculator?
Estimating paint by eye can waste money and time. A paint calculator uses room measurements and paint coverage (square meters per litre) to give a clear result. This helps you buy the right amount of paint for walls, ceilings, and trims.
- Saves money — buy the correct litres and avoid extra cans.
- Reduces waste — less leftover paint to store or throw away.
- Makes planning easy — know cost and material needs before you start.
What the calculator needs (simple inputs)
To use the calculator you should measure these things:
- Room length (meters)
- Room width (meters)
- Room height (meters)
- Total area of doors and windows (square meters) — we subtract this from the wall area
- Number of coats (usually 1–2 for a new job; 2 for full coverage)
- Coverage (m² per litre) — check the paint can label (typical 8–12 m²/L)
- Price per litre — to estimate total cost
How the calculation works (simple math)
We use two main area numbers:
- Wall area = 2 × (length + width) × height
- Ceiling area = length × width
Then we add coats and subtract doors/windows:
Total paint area = (Wall area + Ceiling area − Doors/Windows area) × Number of coats
Litres needed = Total paint area ÷ Coverage (m² per litre)
Round up the litres and add a waste margin (5–10%) if you want extra for touch-ups.
Quick example
Room: 4.0 m (length) × 3.0 m (width) × 2.8 m (height). Doors/windows area = 2.0 sq m. Coats = 2. Coverage = 10 m² per litre.
Wall area = 2 × (4 + 3) × 2.8 = 39.2 sq m
Ceiling area = 4 × 3 = 12.0 sq m
Total area = (39.2 + 12.0 − 2.0) × 2 = 98.4 sq m
Litres needed = 98.4 ÷ 10 = 9.84 → round up to 10.0 litres
If price per litre is $8.00, estimated cost = 10 × $8 = $80.00
Use our free paint calculator
Enter your room size and paint details to get an instant estimate. The calculator shows litres required, suggested can sizes, and a cost estimate.
Practical tips for painting
- Buy primer if walls are patched or there is old paint. Primer improves coverage.
- Choose the right finish: matte for walls, satin for trim, gloss for cabinets.
- Use proper tools: a good roller, angled brush for trim, painter's tape and drop cloths.
- Allow for waste: add 5–10% more paint for cutting and mistakes.
- Check the paint label for exact coverage (m² per litre) and drying time.
Common painting materials & terms
- Coverage — how many square meters one litre of paint covers (m²/L).
- Coats — number of full layers of paint applied.
- Primer — base coat that improves adhesion and hides stains.
- Roller — best for large flat areas like walls and ceilings.
- Brush — for edges, trim, and detail work.
Planning a full renovation? After calculating your paint needs, try our DIY Tile Calculator to estimate the tiles required for your project.
FAQs — fast answers
- Q: Do I include windows and doors?
- A: Subtract the area of doors and windows from the wall area. This lowers paint required.
- Q: How many coats do I need?
- A: Usually 2 coats for a good finish. If you use a strong primer and high-coverage paint, 1 coat may be enough.
- Q: What coverage should I use?
- A: Check the paint can. Typical coverage is 8–12 m² per litre. Use the exact number on the product label in the calculator.
- Q: Should I buy whole cans only?
- A: Most stores sell whole-litre cans. Buy slightly more than needed for touch-ups.
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