Paint Calculator UK
Calculate exactly how much paint you need for any room. Add multiple rooms, choose surface type and number of coats, and get results in UK tin sizes. Export a buying sheet as PDF, CSV or clipboard.
Last reviewed: 30 September 2026
Paint Settings
Rooms
How to Calculate How Much Paint You Need
Working out how much paint you need is simple once you know the method. Here is the process professional decorators use:
- Measure your room: record the length, width and height in metres. A standard UK room might be 4m long, 3m wide and 2.4m high.
- Calculate the wall area: add up all four walls: 2 × (length × height) + 2 × (width × height). For our example: 2 × (4 × 2.4) + 2 × (3 × 2.4) = 19.2 + 14.4 = 33.6 m².
- Subtract openings: a standard UK door is about 0.8 × 2.0m (1.6 m²) and a window about 1.2 × 1.2m (1.44 m²). Subtract these from the total.
- Check the coverage rate: most UK emulsion paints cover 12-14 m² per litre. This is printed on the tin.
- Multiply by coats: two coats is standard. Divide total area by coverage, then multiply by the number of coats.
- Add waste: add 10% for touch-ups, roller absorption and edges.
Our calculator does all of this automatically, including optimal tin size selection to minimise waste and cost.
UK Paint Coverage Rates by Type
Coverage varies by paint type and brand. These are typical rates for UK paints from brands like Dulux, Crown and Johnstone's: Painting wall panelling? Our wall panelling calculator gives the panelled area and the strips you need. Painting before the floor goes down? Our laminate flooring calculator lays out the planks row by row. Fitting slatted wall panels? Our slat wall panel calculator counts the panels and adhesive. Felting a shed roof? Our shed roof felt calculator counts the rolls.
| Paint Type | Coverage (m²/L) | Common Use |
|---|---|---|
| Matt Emulsion | 12-14 | Walls and ceilings: the UK standard for interior decorating |
| Silk Emulsion | 13-15 | Walls in kitchens and bathrooms: wipeable finish |
| Eggshell | 12-14 | Woodwork and walls: subtle sheen, durable |
| Gloss | 14-17 | Doors, skirting boards and window frames |
| Satinwood | 14-16 | Woodwork: softer sheen than gloss |
| Primer / Undercoat | 10-12 | Bare wood, metal and new plaster (after mist coat) |
| Masonry Paint | 6-8 | Exterior brick, render and blockwork |
| Ceiling Paint | 12-14 | Ceiling-specific matt: non-drip formula |
Surface condition also affects coverage. Rough, porous or dark-coloured surfaces absorb more paint and reduce the coverage rate.
UK Standard Paint Tin Sizes
Paint in the UK is sold in standard tin sizes. Choosing the right combination saves money:
- Tester pots (50-75ml): for sampling colours before committing. Not included in calculations.
- 1 litre: enough for small areas like a feature wall or touch-ups. Covers roughly 12 m² per coat.
- 2.5 litres: the most popular UK size. Covers a standard bedroom or bathroom. About 30 m² per coat.
- 5 litres: best value for living rooms and larger spaces. Covers roughly 60 m² per coat.
- 10 litres: trade size for large areas or whole houses. Covers roughly 120 m² per coat. Trade counters like Travis Perkins and Screwfix usually stock this size for professional decorators.
Per-litre price drops significantly with larger tins. If you need 6 litres, a 5L + 2.5L is usually cheaper than three 2.5L tins, but check current prices at B&Q or Wickes.
Mist Coat for New Plaster
If you're painting onto new plaster (including replastered walls), you must apply a mist coat first. A mist coat is emulsion paint diluted with water (typically 70% paint, 30% water) that seals the plaster and gives subsequent coats something to grip.
Why it matters: painting straight onto bare plaster causes the paint to peel, flake and bubble because the plaster is too absorbent. The mist coat soaks in and creates a stable base.
How to apply: mix your emulsion 70:30 with clean water. Apply one even coat with a roller and let it dry for 24 hours. Then apply your topcoats as normal. Do not use vinyl silk or contract matt for the mist coat, use standard matt emulsion.
Our calculator flags when a mist coat is needed and estimates the diluted paint required separately from your topcoats.
How Many Coats of Paint Do I Need?
The number of coats depends on the colour change and surface: Painting new timber cladding? Our cladding calculator works out the boards, so you know the area to paint.
- Same colour refresh: 1-2 coats is usually enough.
- Light over light: 2 coats is standard.
- Dark over light: 2 coats normally covers well.
- Light over dark: 2-3 coats may be needed, or use a stain-blocking primer first.
- New plaster: 1 mist coat + 2 topcoats.
- Bare wood: 1 primer + 2 topcoats.
For best results, always do at least 2 coats. The first coat often looks patchy even on previously painted walls.
Paint Needed by Room Size
| Room | Wall Area | Typical Paint Needed |
|---|---|---|
| Small bedroom / box room (2.5m × 2.5m) | ~20 m² | One 2.5L + one 0.75L tin (about 3.3L needed) |
| Standard bedroom (3.5m × 3m) | ~28 m² | One 5L tin |
| Standard living room (4m × 3.5m) | ~33 m² | One 5L tin is tight for two full coats (about 5.5L needed) - a 0.75L top-up covers the shortfall |
| Large living room / open plan (6m × 4m) | ~44 m² | One 5L + one 2.5L tin (about 7.3L needed) |
Based on two coats at 12 m² per litre, allowing for real-world wall surfaces (Dulux quotes up to 14 m²/L on smooth, sealed walls). A standard door and one window are subtracted from wall area. Ceiling paint is not included. For coverage by tin size and paint type in full, see our Dulux paint coverage by tin size guide.
Frequently Asked Questions
How much paint do I need for a room?
A standard UK room (4m × 3m, 2.4m ceiling) needs roughly 5-6 litres for two coats of emulsion on the walls only. See the room-size table below for more sizes, or use the calculator above for an exact figure based on your measurements.
How far does 5 litres of paint go?
Based on 12 m²/L, allowing for real-world wall surfaces, a 5L tin of standard emulsion covers approximately 60 m² per coat (roughly 30 m² with two coats). Dulux quotes up to 14 m²/L on smooth, sealed walls, but expect less on textured, porous or previously-unpainted surfaces. See our Dulux coverage guide for the breakdown by paint type and tin size.
How much paint do I need for a 3m × 3m wall?
A 3m × 3m wall has 9 m² of area. Based on 12 m²/L, that's around 0.75L per coat or 1.5L for two coats. A 2.5L tin gives you enough with some left for touch-ups.
How much does a 0.75L tin of paint cover?
A 0.75L (750ml) tin covers around 12 m² with one coat for Dulux Quick Dry Satinwood, Quick Dry Gloss or Weathershield Quick Dry Undercoat (all published at up to 16 m²/L), or around 9 m² for Dulux Matt or Silk emulsion (12 m²/L, allowing for real-world surfaces - Dulux quotes up to 14 m²/L on smooth walls). See our full Dulux coverage guide for the breakdown by paint type and tin size.
Should I paint the ceiling the same colour as the walls?
Most UK decorators use brilliant white matt or a dedicated ceiling paint on ceilings. White reflects more light and makes rooms feel larger. If you want the ceiling in the same colour, our calculator lets you include it.
What is the most popular paint in the UK?
Dulux is the UK's best-selling paint brand. Their Matt Emulsion range (including Dulux Walls & Ceilings) is the most widely used for interior walls. Dulux publishes coverage of up to 14 m² per litre for this range.
Is it better to buy more paint than I need?
It's wise to have a small surplus (10%) for touch-ups after moving furniture in. Store leftover paint sealed in a cool, dry place. It lasts 2-3 years unopened. However, large surpluses are wasteful, so use our calculator for an accurate estimate.
Do I need a mist coat on new plaster?
Yes. New plaster must have a mist coat first: emulsion diluted 70:30 with water. This seals the plaster and prevents topcoats from peeling. Let it dry 24 hours before applying your finish coats.
How many coats of paint do I need?
Two coats is standard for most repainting jobs. When painting light over dark you may need 3 coats. New plaster needs a mist coat plus 2 topcoats.