Work out how many litres of paint you need for each room, and which tin sizes to buy. Enter the room dimensions and the number of doors and windows, choose the number of coats and the surface condition, and the calculator gives you wall, ceiling and sealer quantities. It then suggests a sensible combination of 10 L, 4 L, 2 L and 1 L tins.
Paint calculator (metric)
Add each room. Doors (820 × 2040 mm) and windows (1500 × 1200 mm) are deducted at standard sizes; use “other deductions” for anything else. Tick the ceiling box if the ceiling is being painted too.
Paint settings
Litres = area × coats × surface factor ÷ spread rate, plus wastage for trays, rollers and touch-ups. The default 16 m²/L (top coats) and 12 m²/L (sealer undercoat) come from typical Australian interior acrylic datasheets; always check the datasheet for your product. Tins are suggested in 10 L, 4 L, 2 L and 1 L sizes.
Pricing a whole repaint or a new build?
Measure Manage prepares painting take-offs room by room, including doors, trims, ceilings and exterior surfaces, ready for you to price or for us to estimate. Call Alastair on 0498 202 445 for a professional take-off.
How the paint calculator works
- Wall area = room perimeter × wall height, less a standard door (0.82 × 2.04 m) and window (1.5 × 1.2 m) for each one you enter.
- Paint needed = area × coats × surface factor ÷ spread rate (m² per litre), plus wastage.
- Surface factor increases the quantity for porous, rough or textured surfaces such as bare render or face brick.
- Tins are chosen to avoid buying lots of small tins or leaving too much unused.
Painting tips
- Check the spread rate on the tin. Most interior acrylics cover roughly 12–16 m² per litre per coat on smooth, sealed surfaces.
- New render, plaster or bare timber needs a sealer or primer first.
- Two coats is the normal allowance. Strong colour changes may need three.
- Buy all paint for one colour at the same time to avoid batch differences.
What this calculator doesn’t include
- Doors, trims, skirtings and architraves (measure them separately)
- Preparation, filling and sanding
- Labour, rollers, brushes and drop sheets
Frequently asked questions
How much paint will I need for a room?
A 4 × 4 m bedroom with 2.4 m ceilings has about 35 m² of wall after one door and one window. At two coats and 16 m² per litre, that’s about 4.4 litres before wastage. Use the calculator for your exact rooms.
How many square metres does 4 litres of paint cover?
Usually about 48–64 m² for one coat on a smooth, sealed surface, or half that for two coats. Rough or porous surfaces cover less.
How do I estimate the cost of painting a house?
Enter your price per litre for a materials cost, then add primers, sundries and labour. For a full repaint or a new build, a measured take-off is more reliable.
Pricing a full painting package? Measure Manage prepares room-by-room painting take-offs for Perth and WA builders and painters. Call 0498 202 445.