Paint Calculator
Calculate how many litres of paint you need to cover walls and ceilings, accounting for doors and windows.
I built this after buying too little paint for a kitchen repaint and having to make a second trip to find the colour had a slightly different tint. Measure once, buy the right amount — that is all this does.
Paint Calculator
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The paint calculator tells you exactly how many litres of paint to buy for any room. Enter the length, width, and ceiling height of the room, the number of doors and windows, how many coats you plan to apply, and the paint's coverage rate — the result is the litres needed plus a 10% buffer for waste and touch-ups. Buying too little means a second trip to the hardware store mid-project, often to find the batch has a slightly different tint. Buying too much leaves you with unused paint that is difficult to dispose of responsibly. Getting the number right before you shop saves both money and frustration. This calculator is most useful before starting any interior room — bedrooms, living rooms, kitchens, and bathrooms. For ceilings, run the calculation separately using length × width as a flat area (enter 0 for doors and windows). For exterior walls, the same formula applies; just measure the total facade and subtract each window and door opening.
How to Use the Paint Calculator
The Paint Calculator is designed to give you an accurate answer in seconds. Follow these steps:
- 1Choose your unit — select Metric (m) or Imperial (ft) at the top of the calculator. All three dimension fields switch together.
- 2Enter Room Length — measure the longest wall of your room in metres or feet. Round up to the nearest 0.1.
- 3Enter Room Width — measure the opposite wall. For an irregular room, use the longest dimension in each direction.
- 4Enter Ceiling Height — measure floor to ceiling. Standard height is 2.4 m (7.87 ft). Check your own room — older homes often have taller ceilings.
- 5Set Number of Coats — choose 2 for most rooms. Use 1 coat for a very similar colour on a well-prepped surface, or 3 coats when covering a dark colour with a light shade.
- 6Click Calculate — results show Net Wall Area (paintable surface after deducting doors and windows), Paint Required, and a 10% Waste Buffer. Buy the buffer amount.
- 7Need more precision? Click "+ More options" to enter the exact number of doors and windows in your room, and your paint's coverage rate from the tin label.
No account or sign-up required. All calculations run locally in your browser — nothing is stored or transmitted to any server.
How It Works
Litres = ((2 × (L + W) × H) − Doors − Windows) × Coats ÷ Coverage
How to use the paint calculator: 1. Room Length and Room Width — Measure your room from wall to wall. Use metres (default) or switch to Imperial for feet. Measure at the longest point in each direction and round up to the nearest 0.1 m. 2. Ceiling Height — Measure from floor to ceiling. Standard ceiling height is 2.4 m. Older homes or period properties may have 2.7 m or higher ceilings — always measure rather than assume. 3. Number of Coats — How many coats you plan to apply. Most rooms need 2 coats for solid, even coverage. Use 1 coat only when repainting a very similar colour over a well-prepared surface. Use 3 coats when covering a dark colour with a light shade, painting bare plaster, or using a low-coverage paint. 4. Click Calculate — The results show the net paintable wall area (after subtracting doors and windows), the exact litres needed, and a 10% buffer amount. Always buy the buffer figure — it covers waste, cutting in at edges, and future touch-ups. Advanced options (click "+ More options" to reveal): - Number of Doors: Count each door in the room. The calculator deducts 1.9 m² per door (standard interior door area) from the total wall area. - Number of Windows: Count each window. The calculator deducts 1.2 m² per window. - Paint Coverage (m²/L): The area one litre covers in a single coat. Standard emulsion covers 10–12 m²/L; gloss and satin cover 9–11 m²/L; textured and masonry paints cover 5–8 m²/L. Find the exact figure on your paint tin label and enter it for the most accurate result.
Frequently Asked Questions
How many litres of paint do I need for a room?
A standard bedroom (4 m × 3.5 m, 2.4 m ceiling, 1 door, 1 window) needs approximately 7–8 litres for two coats at 10 m²/litre coverage. A larger living room (6 m × 5 m) needs 12–14 litres for two coats. Always add 10% for waste, cutting in, and touch-ups after the job is complete.
How many coats of paint does a room need?
Most paint jobs require two coats for even, opaque coverage. One coat may suffice when painting a similar or slightly lighter colour over a well-prepared surface. Three coats are needed when painting over a dark colour with a light shade, over bare plaster, or when using a low-coverage paint. A primer coat before the topcoat significantly reduces the number of topcoats needed on new or repaired surfaces.
What is the coverage rate of paint?
Coverage rate is the area one litre of paint covers in a single coat. Standard emulsion and wall paints typically cover 10–12 m² per litre. Premium paints may cover 12–14 m² per litre. Textured, masonry, and exterior paints cover less — often 5–8 m²/litre. Check the specific tin you are buying; coverage varies by product and is listed on the label.
Should I buy paint in 2.5L or 5L tins?
Buy the combination that gets you just above your calculated requirement. Most paint brands sell in 1L, 2.5L, 5L, and 10L tins. If you need 7.8 litres, buying one 5L + one 2.5L + one 500ml sample is cheaper than two 5L tins and leaves minimal waste. Importantly: buy all tins from the same batch number to ensure consistent colour across the whole room.
Is the paint calculator free?
Yes — free with no sign-up needed. Enter your room dimensions, door and window counts, and coverage rate for an instant litre estimate with a 10% waste buffer. All calculations run in your browser and no data is stored.
How much does 5 litres of paint cover?
A standard 5 litre tin of emulsion paint covers approximately 50–60 m² in a single coat, or 25–30 m² in two coats. Coverage varies by paint type and surface: matt emulsion at 10–12 m²/L gives 50–60 m² from 5L; silk emulsion at 9–11 m²/L gives 45–55 m²; gloss at 9–11 m²/L gives 45–55 m²; masonry paint at 5–8 m²/L gives only 25–40 m² from a 5L tin. A 2.5L tin covers half these figures: approximately 25–30 m² (one coat) or 12–15 m² (two coats) for standard emulsion. A 1L tin covers 10–12 m² in a single coat — useful for accent walls, doors, or small areas. Always check the exact coverage rate on your specific tin label, as premium and economy paints differ significantly.
What is the coverage rate of emulsion paint?
Standard matt emulsion paint covers 10–12 m² per litre per coat. Silk and satin emulsion covers 9–11 m²/L. Premium paints from Dulux, Farrow & Ball, and Little Greene may cover 12–14 m²/L due to higher pigment concentration. Budget emulsion can drop to 8–10 m²/L. For reference: eggshell 9–11 m²/L; gloss 9–11 m²/L; undercoat 9–11 m²/L; primer 9–12 m²/L; masonry paint 5–8 m²/L (rough surfaces absorb more). The coverage figure assumes a well-prepared surface — bare plaster, heavily textured walls, or porous surfaces reduce coverage by 20–30% on the first coat. Always use the figure printed on your specific tin as the reference for calculating quantities.
How do I calculate how much paint I need for one wall?
Multiply the wall width by the wall height to get the area in m², subtract any doors and windows, then divide by the paint coverage rate (m²/L) and multiply by the number of coats. Example: a wall 4.5 m wide × 2.4 m high = 10.8 m². One standard window (1.2 m²) gives 10.8 − 1.2 = 9.6 m² to paint. At 10 m²/L coverage with 2 coats: 9.6 ÷ 10 × 2 = 1.92 litres — buy a 2.5L tin to include a buffer. Add 10% to your total for waste and touch-ups. For an accent wall painted a different colour, this per-wall calculation is the most useful approach.
How much paint do I need for a ceiling?
Measure the ceiling length × width to get the area in m², then divide by the coverage rate and multiply by the number of coats. Ceilings typically need 2 coats because ceiling white is applied at a higher dilution and the surface is harder to cover evenly. Example: a 5 m × 4 m ceiling = 20 m². At 10 m²/L coverage with 2 coats: 20 ÷ 10 × 2 = 4 litres — buy a 5L tin. Ceiling paint (usually bright white or brilliant white) has a coverage rate of 10–12 m²/L, similar to standard emulsion. Use the paint calculator above and enter 0 for doors and windows when calculating a ceiling.
How much paint do I need for a 10×10 room?
A 10×10 foot room (approximately 3 m × 3 m) with a standard 2.4 m ceiling has about 28 m² of wall area. Subtracting one door (1.9 m²) and one window (1.2 m²) leaves roughly 25 m² to paint. At 10 m²/L coverage with 2 coats, you need approximately 5 litres of paint — buy a 5L tin plus a small buffer for edges and touch-ups. If painting in feet rather than metres, convert first: 10 ft ≈ 3.05 m. This room size is common for UK box rooms, small bedrooms, and home offices.
How much paint do I need for a 12×12 room?
A 12×12 foot room (approximately 3.7 m × 3.7 m) with a 2.4 m ceiling has about 35 m² of wall area. Subtracting one door (1.9 m²) and one window (1.2 m²) leaves roughly 32 m² to paint. At 10 m²/L coverage with 2 coats, you need approximately 6.4 litres — buy two 2.5L tins (5L) plus a 1L top-up, or a single 5L tin and check if you have leftover from a previous job. A 12×12 room is a common size for UK double bedrooms and US standard bedrooms.
How much paint do I need for a door?
A standard interior door is approximately 1.98 m × 0.76 m = 1.5 m² per side, or 3 m² for both sides. At 10 m²/L coverage with 2 coats, both sides of one door require about 0.6 litres. A 750 ml tester pot or 1L tin is sufficient for a single door in 2 coats including a small buffer. For gloss or eggshell finishes (used on doors and woodwork), coverage drops slightly to 9–10 m²/L. If painting 4–5 doors in the same colour, a 2.5L tin covers them all comfortably.
How much paint do I need for a fence?
A standard fence panel is 1.83 m wide × 1.83 m tall = 3.35 m² per panel, or 6.7 m² for both sides. Fence paint and timber stain have lower coverage rates than interior emulsion — typically 5–8 m²/L — because rough, porous wood absorbs more product. For a 10-panel fence (one side only, 33.5 m²) at 6 m²/L coverage: 33.5 ÷ 6 = 5.6 litres per coat. With 2 coats, buy 11–12 litres. Most fence paint is sold in 5L and 9L tins; two 5L tins would suffice for 10 panels in 2 coats. Measure each panel and enter the total area in the paint calculator above for an exact figure.