How much paint do I need?
The calculator works out the paintable area of your walls (perimeter × height), takes off about 1.9m² per door and 1.5m² per window, adds the ceiling if selected, then multiplies by the number of coats and divides by the paint's coverage:
We add 10% for roller loss and absorbent patches. The tin suggestion picks the cheapest combination of 5L and 2.5L tins based on the prices you enter.
Paint coverage guide
| Paint | Coverage per litre | 5L tin covers (1 coat) |
|---|---|---|
| Standard matt / silk emulsion | 10–13 m² | ~60 m² |
| Premium durable matt | 13–16 m² | ~70 m² |
| One-coat emulsion | ~10 m² | ~50 m² |
| Masonry paint (smooth) | 6–8 m² | ~35 m² |
| Masonry paint (pebbledash) | 3–5 m² | ~20 m² |
Painting tips
- Paint the ceiling first, then the walls, then woodwork (skirting, doors and frames).
- "Cut in" around edges with a brush before rolling, working one wall at a time so the edges blend while wet.
- Box your tins: if you have more than one tin of the same colour, mix them together in a bucket for a consistent shade.
- Bare plaster needs a mist coat first. Stains, damp patches and nicotine need a stain-block primer.
Worked examples
A 4m × 3m bedroom: the walls are 2 × (4 + 3) × 2.4m = 33.6m². Take off about 1.9m² for the door and 1.5m² for the window and that leaves 30.2m². Two coats at 12m² per litre, plus 10%, is 5.5 litres. A 5L tin alone would leave you short on the second coat, so the calculator suggests the cheapest way to reach 5.5L at your prices. Tick "Paint the ceiling" to add the 12m² ceiling, which needs about 2.2 litres more.
The front of a house: an 8m × 5m wall with four windows and a door is about 34m². In smooth masonry paint (around 7m² per litre) two coats take about 11 litres. If the wall is pebbledash, it's nearer 19 litres, because rough surfaces soak up far more paint.
Which finish where?
- Matt: hides small wall imperfections, so it's the usual choice for living rooms, bedrooms and ceilings. Choose a "durable" or "scrubbable" matt in hallways.
- Silk: slightly shiny and easier to wipe, but it shows every bump and patch.
- Kitchen and bathroom paints: moisture- and mould-resistant, usually with a soft sheen. Worth it in rooms that get steamy.
- Woodwork: satin or gloss, water- or solvent-based. A litre usually does the skirting and door frames of an average room.
Preparation matters more than paint
Fill cracks and holes, sand the filler flush, and wash greasy areas (kitchens, around switches) with sugar soap. Cover the floor and mask the edges. On new plaster, let it dry fully, then apply a mist coat. Our plaster calculator explains drying times. Good preparation is the difference between two coats and four.
Common painting mistakes
- Buying too little in one go. A second batch of a mixed colour can look different. Buy it all at once and box the tins.
- Going light over dark in two coats. A strong colour change often needs a third coat or a primer first. Set coats to 3 above to see the difference.
- Painting over damp. Damp patches stain through and the paint peels. Find and fix the cause first.
Mixing paint and paper? The wallpaper calculator handles feature walls. The redecorating planner combines paint, paper, skirting and flooring into one shopping list.