Quick answer: One litre of paint covers roughly 16m² per coat. For walls, take the total wall area, subtract doors and windows, then multiply by the number of coats (usually 2) and divide by 16 to get litres. This calculator does it for walls, ceilings and trim in one go.
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Paint Calculator
m²
coats
Paint Calculation Formula
Paint Required: (Wall Area × Number of Coats) / Coverage Rate
Paint + Waste: Paint Required × 1.1
Paint + Waste: Paint Required × 1.1
Paint Calculator: Walls, Ceilings & Trim
Material waste accounts for 10–15% of total construction costs on Australian sites (Master Builders, 2025). Calculating paint quantities accurately eliminates unnecessary spend and reduces job-site waste.
Paint Coverage Rates
| Paint Type | Coverage (m²/L) | Typical Coats | Litres per m² |
|---|---|---|---|
| Ceiling Flat | 12–14 | 2 | 0.15 |
| Interior Low Sheen | 12–16 | 2 | 0.14 |
| Interior Semi Gloss | 14–16 | 2 | 0.13 |
| Exterior Acrylic | 10–14 | 2 | 0.17 |
| Trim / Gloss Enamel | 14–16 | 2 | 0.13 |
| Primer / Sealer | 10–12 | 1 | 0.09 |
Quick Reference: Standard Room Sizes
| Room | Wall Area (m²) | Ceiling (m²) | Paint Needed (L) |
|---|---|---|---|
| Bedroom (3m × 4m) | 33.6 | 12 | ~6.5 L |
| Living Room (5m × 6m) | 52.8 | 30 | ~12 L |
| Bathroom (2.5m × 3m) | 15.4 | 7.5 | ~3.5 L |
| Whole House (3-bed) | ~250 | ~120 | ~55 L |
Tips for Accurate Paint Estimating
- Deduct 50% for windows and doors: a standard door is ~1.6 m², a window ~1.2 m².
- Textured walls and bare plaster absorb more: add 15–20% extra.
- Dark-over-light colour changes may need 3 coats instead of 2.
- Always check the product data sheet for actual spread rate.
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