Short answer
A 3.5 x 3 m bedroom with a 2.4 m ceiling, one door and one window needs about 5.1 litres of wall paint and 1.9 litres of ceiling paint for two coats, including 10% spare. That is 1 x 4 L + 1 x 2 L of wall paint and 1 x 2 L of ceiling paint. The sum is wall area x coats ÷ litres covered per litre, and the calculator below does it for any rooms and shows the tins to buy and an indicative price.
Use this free paint calculator to work out how many litres of wall paint, ceiling paint and primer you need, which tins to buy, and roughly what it will cost at Bunnings prices. Measure room by room, or enter a total wall area for an exterior or a whole house.
Paint calculator
Coverage figures on paint tins are “up to” claims for smooth, previously painted surfaces, and the tin label is the final word for your product. Prices are indicative Bunnings prices per litre. Ranges reviewed October 2026.
How to calculate how much paint you need
- Wall area: (room length + width) x 2 x ceiling height, minus doors and windows. Use 1.67 m² for a standard internal door and about 1.5 m² for a window.
- Ceiling area: room length x width.
- Litres per coat: area ÷ coverage per litre. Multiply by the number of coats, then add about 10% spare for touch-ups and uneven surfaces.
- Tins: round up to the tins you can buy, because leftover paint is useful for repairs and a second batch can differ slightly in colour.
| Example (2 coats, 12 m²/L, 10% spare) | Walls | Ceiling | Primer |
|---|---|---|---|
| Bedroom 3.5 x 3 m, 2.4 m ceiling, 1 door, 1 window | 28.0 m², 5.1 L | 10.5 m², 1.9 L | none |
| Living room 5 x 4 m, 2.7 m ceiling, 1 door, 2 windows | 43.9 m², 8.1 L | 20.0 m², 3.7 L | none |
| Same bedroom as new plasterboard (sealer at 10 m²/L) | 28.0 m², 5.1 L | 10.5 m², 1.9 L | 4.2 L |
| Three identical bedrooms 3.5 x 3 m | 84.1 m², 15.4 L | 31.5 m², 5.8 L | none |
How far does a litre of paint go?
Coverage depends on the product and the surface. Every manufacturer quotes an “up to” figure for a smooth, previously painted surface, and the tin label is the authority for the paint you choose.
| Surface | Stated coverage per litre per coat | Calculator default |
|---|---|---|
| Interior walls | Up to 12 m² (Taubmans Endure Interior) to 16 m² (Taubmans Easycoat; the Dulux calculator assumes 16) | 12 m² |
| Ceilings | Up to 16 m² (Taubmans and Dulux ceiling white) | 12 m² (change to 14 or 16 for a best case) |
| Primer or undercoat | About 12 m² (the Dulux calculator’s allowance for a prep coat) | 12 m² |
| New plasterboard sealer | No Australian manufacturer figure found, so this is a cautious estimate | 10 m² |
| Exterior acrylic on smooth surfaces | Up to 16 m² (Dulux Weathershield, Taubmans Sunproof) | 12 m² cautious, 16 m² best case |
| Rough render, brick or weatherboard | No manufacturer figure; Dulux says to allow more paint on these surfaces | 8 m² (an estimate) |
| Semi-gloss trim | Up to 16 m² (Taubmans water-based enamel) | Not included |
How many coats do you need?
- Normal repaint: two topcoats. Manufacturers such as Dulux and Taubmans specify two coats for previously painted surfaces.
- New plasterboard: a sealer or undercoat and two topcoats, which is the minimum under AS/NZS 2311 as quoted by Dulux.
- Dark to light colour change: primer and two topcoats, with a possible third topcoat if the old colour shows through. There is no single manufacturer figure, so check the tin and test a patch.
- Exterior: two coats on a clean, sound surface.
Tin sizes and prices at Bunnings
Wall, ceiling and exterior paint is most often sold in 4, 10 and 15 litre tins, with 1 and 2 litre tins mainly for trim and small jobs. These are listing prices seen at Bunnings in October 2026. Prices vary by colour, store and base, larger tins cost less per litre, and we did not find Paint Place or Dulux Trade Centre prices.
| Paint | Example product and tin | Price | Per litre |
|---|---|---|---|
| Budget wall paint | Spring Low Sheen, 10 L | $75.50 | $7.55 |
| Mid-range wall paint | Taubmans Easycoat, 15 L | $209.99 | $14.00 |
| Premium wall paint | Taubmans Endure, 15 L | $272.90 | $18.19 |
| Premium wall paint | Dulux Wash&Wear, 15 L / 10 L / 4 L | $289 / $239 / $107 | $19.27 / $23.90 / $26.75 |
| Ceiling paint | Dulux Ceiling White, 10 L / 4 L | $163 / $69.99 | $16.30 / $17.50 |
| Ceiling paint | Taubmans Easycoat Ceiling, 15 L | $169.90 | $11.33 |
| Primer | Dulux 1Step Prep, 10 L | $230 | $23.00 |
| Exterior acrylic | Dulux Weathershield, 15 L | $306 | $20.40 |
| Semi-gloss trim | Dulux Aquanamel, 4 L | $125 | $31.25 |
Paint is only part of the cost of a paint job. For labour, see the painting cost calculator and the painter rates page.
Preparing safely: lead and asbestos
- Lead paint: homes built before 1970 may contain lead paint. Test before you disturb it, avoid dry sanding and heat guns, use wet methods and a suitable respirator, and keep children and pregnant women away. See the NSW EPA lead advice.
- Asbestos: homes built before about 1990 may contain asbestos in fibro sheeting, eaves, gutters and wet areas. Never dry sand, high-pressure wash or cut suspect material, and have it tested first. See the Asbestos Safety and Eradication Agency guidance for renovators.
Drying and recoat times
For several Dulux and Taubmans interior and exterior paints, touch dry is about 20 to 30 minutes and recoat is about 2 hours at 25°C and 50% humidity. Cooler or more humid weather takes longer, so check the tin.
Common mistakes
- Assuming the “up to” coverage. Porous, new or rough surfaces use much more paint than the label suggests.
- Forgetting the second coat. Two coats are the norm, and the calculator multiplies the litres for you.
- Skipping the sealer on new plasterboard or bare timber. The topcoat soaks in unevenly and you end up using more paint.
- Running out mid-wall. Buy a little extra, and mix tins of the same colour together before you start so the colour is consistent.
- Using wall paint on the ceiling. Ceiling paint is made for the job and often costs less per litre.
- Sanding old paint without testing it. See the lead and asbestos notes above.
Frequently asked questions
How much paint do I need for a 3.5 x 3 m bedroom?
With a 2.4 m ceiling, one door and one window, the walls are about 28.0 m² after deductions. Two coats at a cautious 12 m² per litre, plus 10% spare, is about 5.1 litres for the walls and 1.9 litres for the ceiling. Buying 1 x 4 L + 1 x 2 L for the walls and 1 x 2 L for the ceiling covers it.
How many square metres does a 4 litre tin of paint cover?
About 48 m² for one coat at a cautious 12 m² per litre, or 64 m² at the 16 m² per litre that many tins claim as a best case. Two coats halve that, so a 4 litre tin paints roughly 24 to 32 m² of wall.
How many coats of paint do I need?
Two topcoats for a normal repaint. New plasterboard needs a sealer or undercoat plus two topcoats, which is the minimum under AS/NZS 2311 as quoted by Dulux. For a big colour change use a primer and two topcoats, and allow for a third topcoat if the new colour is much lighter. Exteriors on a clean, sound surface usually take two coats.
Do I need to prime before painting?
Yes for new plasterboard, bare timber, patched areas, stains and large colour changes. A normal repaint over sound, clean paint usually does not need a separate primer, but follow the label of the paint you buy.
Why does the calculator use 12 m² per litre when the tin says 16?
Tin figures are “up to” claims for a smooth, previously painted surface, and real coverage is lower on porous or rough surfaces. Taubmans Endure Interior, for example, states up to 12, while Taubmans Easycoat states up to 16, and the Dulux calculator assumes 16. We default to 12 so you do not run short, and you can switch to 16 if you want a best-case figure.
How do I measure a room for paint?
Add the length and width of the room, double it, and multiply by the ceiling height to get the wall area. Subtract doors and windows. We use 1.67 m² for an internal door (the common 2040 x 820 mm size) and 1.5 m² for a window, so measure any large windows and use the total wall area option to enter them exactly.
Is it safe to sand old paint?
Not until you know what is in it. Homes built before 1970 may contain lead paint and homes built before 1990 may contain asbestos in fibro sheeting, eaves and wet areas. Test first, avoid dry sanding and heat guns, and use wet methods and the right respirator, as the NSW EPA advises.
Related tools
- Painting cost calculator - what a painter would charge for the same job
- Painter rates - hourly rates and typical job prices
- Materials calculator - quantities for floors, paint and tiles
- Renovation quote comparator - paste painting quotes for red-flag analysis
Related reading: How to Paint Interior Walls (2026 Guide) (how to paint interior walls and what it costs).
Stay in the loop
One short email per month with what has changed in Australian renovation pricing and rules. No spam.