Paint Calculator
Litres of paint for walls and ceilings.
Your Room
Litres and tins update as you type.
Check your tin: most interior acrylics state roughly 12–16 m²/L per coat.
Wall & ceiling paint needed
5.2 L
- Walls: buy 1 × 4 L + 1 × 2 L
Per-surface breakdown
| Surface | Area | Per coat | Total | Buy |
|---|---|---|---|---|
| Walls14 m²/L | 32.9 m² | 2.58 L | 5.17 L | 1 × 4 L + 1 × 2 L0.8 L spare |
Walls: 36 m² gross − 3.1 m² of doors and windows = 32.9 m².
Tins chosen from 15, 10, 4, 2, 1 L sizes for the least paint bought, then the fewest tins.
Time is a rough DIY guide: about 10 m² per hour per coat (6.5 hours painting) plus 2 hours drying between coats (2 hours). Prep, cutting-in detail and clean-up aren't included.
| Room | Wall area | Litres | Buy |
|---|---|---|---|
| Small bedroom3 × 3 × 2.4 m | 25.7 m² | 4 L | 1 × 4 L + 1 × 1 L |
| Bedroom4 × 3.5 × 2.4 m | 32.9 m² | 5.2 L | 1 × 4 L + 1 × 2 L |
| Living room5 × 4 × 2.4 m | 40.1 m² | 6.3 L | 1 × 4 L + 1 × 2 L + 1 × 1 L |
Walls only, 2 coats, 1 door and 1 window, at your coverage (14 m²/L) and wastage (10%).
How to Use the Paint Calculator
Enter the room's length, width and wall height, tick the surfaces you're painting, and say how many doors and windows to leave out. The paint calculator works out the area, the litres for each product (wall paint, ceiling white, floor paint and door enamel), the best mix of tins to buy, a cost estimate if you add a price per litre, and a rough painting time. For a feature wall or an odd-shaped space, switch to Area and enter the square metres directly.
How Much Paint Do I Need? The Formula
Ceiling and floor area = length × width. Each door opening defaults to 0.82 × 2.04 m and each window to 1.2 × 1.2 m.
Worked out separately for walls, ceiling, floor and doors, then rounded up to 1, 2, 4, 10 and 15 L tins.
Worked Example: A Bedroom
A 4 × 3.5 m bedroom with 2.4 m walls has a perimeter of 15 m, so the gross wall area is 36 m². Take off one door (1.67 m²) and one window (1.44 m²) and there's 32.89 m² of wall to paint. At 2 coats, 14 m²/L and 10% wastage, the walls need 5.17 L — buy a 4 L and a 2 L tin.
The 14 m² ceiling needs 2.2 L of ceiling paint — a 2 L and a 1 L tin. That's 7.37 L in total (about 3.68 L per coat), with 9 L bought and roughly 1.6 L left for touch-ups. Painting 46.89 m² twice at about 10 m² an hour takes around 9.5 hours, or 11.5 hours including 2 hours of drying between coats.
Paint Coverage and Choosing Products
Different surfaces normally take different paints, which is why the calculator lists them separately. Walls usually get a low-sheen or matt interior acrylic, ceilings a flat ceiling white, doors and trim an enamel or semi-gloss, and floors a dedicated floor or concrete paint with lower coverage. If you're painting new plaster, apply a sealer or undercoat first — bare plaster is very porous and will otherwise drink the topcoat. Going from a dark colour to a light one, or using a deep colour, may need a tinted undercoat or an extra coat.
Spare paint is useful: seal the lid firmly, write the colour and room on the tin, and store it upright in a cool, dry place. Check with your local council for how to dispose of paint you no longer need.
Frequently Asked Questions
- How much paint do I need?
- Work out the area you're painting in square metres, multiply by the number of coats, then divide by the coverage on the tin (m² per litre). For walls, that's the room's perimeter times the wall height, minus doors and windows. Add about 10% for wastage, then round up to the tin sizes you can actually buy — the paint calculator does all of this for you.
- How does a how much paint calculator work out tin sizes?
- It takes the litres needed for each product and finds the mix of common Australian tin sizes (1, 2, 4, 10 and 15 L) that buys the least paint while still covering the job, then picks the option with the fewest tins. For example, 7.3 L becomes two 4 L tins rather than 4 + 2 + 2 L. Not every range comes in every size, so check what your brand stocks.
- What is paint coverage, and why does it vary?
- Paint coverage (or spread rate) is how many square metres one litre covers in one coat. Most interior acrylics state roughly 12–16 m²/L, but porous surfaces, new plaster, rough or textured walls, and big colour changes (especially dark to light) soak up more paint or need extra coats. New plaster should get a sealer or undercoat first, which is a separate product with its own coverage.
- How many coats of paint do I need?
- Two coats is the usual recommendation for interior walls and ceilings — it gives even colour and a durable finish. One coat can be enough for a fresh coat in the same colour over sound paint. Plan on three coats, or a tinted undercoat plus two, when covering a dark colour with a light one or painting strong, deep colours.
- How much paint to paint a door?
- A standard 0.82 × 2.04 m internal door is about 3.35 m² for both sides. At 14 m²/L with two coats and 10% wastage that's around 0.53 L, so a 1 L tin usually does one door with some left over. Doors and trim are normally done in a separate enamel or semi-gloss, so the calculator gives them their own tin list.
- How much paint for a bedroom?
- A typical 4 × 3.5 m bedroom with 2.4 m ceilings, one door and one window has about 32.9 m² of wall. Two coats at 14 m²/L plus 10% wastage needs about 5.17 L — a 4 L and a 2 L tin. A small 3 × 3 m bedroom needs about 4.04 L, and the ceiling (usually a separate ceiling white) adds about 2.2 L for the larger room.
- Can I use this as a floor paint calculator?
- Yes — tick Floor and enter your floor paint's coverage. Floor and garage paints usually spread less far than wall paint, so the calculator defaults to 8 m²/L for floors; check the tin, as epoxy and some concrete coatings differ again. A 4 × 3.5 m floor at two coats and 10% wastage needs about 3.85 L at that rate.
- How long does it take to paint a room?
- As a rough DIY guide, allow about 10 m² per hour per coat with a roller, plus drying time between coats — often around 2 hours for water-based paint, but check the tin. A 4 × 3.5 m bedroom's walls and ceiling at two coats works out to roughly 9.5 hours of painting plus 2 hours drying. Prep, masking, patching and clean-up add more time.
- Should I buy all my paint at once?
- Yes, where you can. Buying enough from the same batch (or having it all tinted at the same time) helps keep the colour consistent across the room. Leftover paint keeps for touch-ups if the lid is sealed tightly and the tin is stored upright somewhere cool and dry, away from frost and direct heat.