Room Paint Calculator Australia — Walls, Ceiling & Deductions
Room dimensions
Standard door ≈ 2.0 × 0.9 m · Standard window ≈ 1.2 × 1.0 m
Paint required
This room paint calculator works out the exact litres of paint needed for an Australian room by calculating total wall area, adding the ceiling if required, then deducting the area of any doors and windows. Room dimensions are entered in metres — the standard used by Australian builders and painters. Coverage rates reflect typical Australian interior paint products: 16 m²/L on smooth plasterboard, 12 m²/L on rendered or medium-texture walls, and 8 m²/L on rough or porous surfaces. The tool is brand-neutral — confirm the spread rate on your specific product's data sheet before ordering. Always buy in the largest available can size to minimise cost per litre and reduce colour-match risk.
Frequently Asked Questions
Should I use the same paint for walls and ceiling?
Not usually. Ceiling paint is typically flat or low-sheen white, formulated to hide roller lines on horizontal surfaces. Wall paint is available in flat, low-sheen, semi-gloss, and gloss finishes depending on the room type. Most Australian painters use a separate ceiling white and a wall paint in the chosen colour and sheen level. Both quantities can be calculated using this tool by running it separately for ceiling and walls.
Do I need to deduct doors and windows from my paint calculation?
Yes, for accuracy. A standard 2040 × 820 mm door accounts for about 1.7 m², and a typical 1200 × 1000 mm window is 1.2 m². On a small room these deductions can represent 10–15% of the total wall area. This calculator lets you add as many openings as needed to get an accurate net paintable area.
How many coats does new plasterboard need in Australia?
New plasterboard (also called plaster, gyprock, or drywall) is highly porous and typically requires a sealer or primer coat before two topcoats — three coat layers in total. Skipping the sealer leads to uneven sheen and excessive paint consumption. Some premium paints marketed as "paint and prime in one" can reduce this to two coats on new plasterboard — check the product data sheet.
What paint sheen is right for different rooms?
In Australian residential practice: flat or low-sheen for living rooms and bedrooms; low-sheen or semi-gloss for kitchens and bathrooms (easier to wipe clean); semi-gloss or gloss for trims, architraves, and doors. High-humidity areas like bathrooms should use a mould-resistant formula. Gloss finishes highlight surface imperfections, so wall preparation is more critical.
How do I calculate paint for a room with a feature wall?
Calculate the feature wall separately using the Paint Coverage Calculator with the feature wall area, then use this room calculator for the remaining three walls with doors and windows deducted as usual. This gives you accurate quantities for each colour without mixing them into a single estimate.
How to use this calculator
- Enter room dimensions — measure room length, width and ceiling height in metres. Standard Australian ceiling height is 2.4 m; newer homes often have 2.7 m or 3.0 m ceilings.
- Toggle ceiling painting — enable this option if you're painting the ceiling. The ceiling area is calculated from room length × width.
- Enter openings — add each door (typically 2.0 × 0.9 m = 1.8 m²) and window (use actual dimensions) to deduct from the paintable wall area.
- Set number of coats — 2 coats is standard for most interior walls; 3 coats may be needed when changing to a drastically different colour or painting over bare plaster.
- Select surface type — previously painted surfaces achieve higher coverage rates than bare or rough surfaces.
- Read the result — litres for walls and ceiling separately, plus suggested tin sizes.
Worked example: Bedroom 4 m × 3.5 m × 2.4 m ceiling, ceiling included, one door (1.8 m²), one window (1.5 m²), 2 coats, standard surface. Wall area = 2×(4+3.5)×2.4 − 1.8 − 1.5 = 33.6 m². Ceiling = 14 m². Total paintable area = 47.6 m². At 12 m²/L × 2 coats = 7.93 L total. Buy two 4 L tins (8 L — just enough), or a 10 L tin for safety.
Understanding your results
The calculator returns litres for walls and ceiling separately, useful if you're using different products — e.g. flat ceiling white for the ceiling and low sheen for the walls, a very common Australian approach. The totals include your nominated number of coats.
Coverage rates assume standard roller application. Painting into a heavily textured surface will reduce the coverage you achieve in practice. If your walls have a texture coat (sand finish, trowelled render), select "rough" surface type to account for the additional surface area of the texture.
Opening deductions are based on the dimensions you enter. For large bay windows or floor-to-ceiling glazing, deducting the full glazed area significantly reduces your paint requirement. For doors with feature architraves you're not painting, use the rough opening dimensions.
Common mistakes: Forgetting to deduct large windows and glazed doors (overstating paint required), using the wrong surface type (smooth vs standard vs rough makes a significant difference), and not buying a small buffer — running out before the second coat is complete is easily avoided by buying the next tin size up.
Room painting in Australia — preparation, sequence and product selection
Painting a room is one of the most cost-effective ways to transform an Australian home. The quality of the outcome is almost entirely determined by preparation and product selection. A poorly prepared room will look disappointing even with expensive paint. A well-prepared room looks great with mid-range products.
Preparation sequence
Follow this order for best results: (1) Fill all holes, cracks and dents with lightweight filler (Polyfilla or equivalent); sand smooth when dry. (2) Sand back any raised paint edges or rough patches. (3) Clean walls with a damp cloth — particularly important in kitchens where grease builds up. (4) Apply masking tape to skirtings, door frames, window reveals and ceiling/wall junctions. (5) Apply primer/sealer to any bare filler or newly exposed plaster before top-coating — skip this and you'll see visible patches ("picture framing") through your finish coat.
Ceiling first, then walls
Always paint ceilings before walls. Splatter from ceiling rolling falls on unprotected floor (covered with drop sheets) rather than on freshly painted walls. Ceiling white is traditionally a flat/matte finish which minimises reflection and hides surface irregularities. Paint walls after ceilings are dry — cut in along the ceiling junction carefully. Paint skirtings, door frames and architraves last.
Interior paint sheen levels
- Flat/matte: Hides surface imperfections, lowest durability, hard to wipe clean — best for ceilings only
- Low sheen: The most common Australian interior wall finish; washable, hides minor imperfections, good general durability
- Semi-gloss: Used for trims, doors and wet areas; highly washable and moisture-resistant
- Gloss: Maximum durability and washability; most common on doors, window frames and trim joinery
Australian climate considerations
In tropical or subtropical Australia (Queensland, NT, coastal NSW), humidity is a real factor. Use paints with anti-mould formulations in bathrooms and laundries — standard interior low sheen is not adequate in persistently humid areas. In the dry heat of inland Australia, water-based paints can dry very quickly — add a flow additive (Floetrol is popular with Australian painters) to extend open time and reduce lap marks in hot conditions.
Australian standards and references
- AS/NZS 2311:2017 — Guide to the painting of buildings (surface preparation, primer selection, number of coats, and coverage rates for Australian conditions)
- AS/NZS 2310:2002 — Glossary of paint and painting terms
- Master Painters Australia (MPA) — Painting specification system and contractor training standards
- HIA (Housing Industry Association) — Guidance on paint quality standards for new residential construction handover
- Dulux, Taubmans, Haymes, Wattyl, Solver — Australian paint brands with interior product ranges formulated for Australian humidity, UV, and temperature cycling; refer to individual product TDS for coverage rates