How Much Paint Do You Need? Room by Room Coverage Guide
By Designer Home Interiors - Designer Paint & Wallpaper | Lick | Published: 2026-10-14
Category: How-to Guides
Learn how to estimate paint for a room with a simple wall area method. Get litres of paint per room and avoid buying too much or too little.
Quick answer
To estimate paint for a room, measure the total wall area and divide by the coverage rate on the tin. Most interior paints cover about 10–12 square metres per litre per coat. Multiply by the number of coats, then round up to the nearest tin size.
Measure wall area, not floor area
Start by measuring the length of each wall and the ceiling height. Multiply length by height to get the gross wall area. Add all walls together, then subtract the area of doors and windows. For example, a 4 m by 5 m room with 2.4 m ceilings has a gross wall area of 43.2 m². Subtract a door (about 1.8 m²) and two windows (about 3 m² total) to get roughly 38.4 m² of paintable wall. This is the number you use for paint quantity.
Check the coverage rate on your paint
Coverage varies by brand and finish. A matt emulsion might cover 12 m² per litre, while an eggshell could cover 10 m² per litre. Always read the tin. If you are using Lick paint, check the product page for the stated coverage. Do not assume all paints are the same. A lower coverage rate means you need more litres for the same wall area.
Calculate litres per coat and total paint
Divide your paintable wall area by the coverage rate. For 38.4 m² at 12 m² per litre, you need 3.2 litres per coat. For two coats, that is 6.4 litres. If you are painting the ceiling, add its area separately. For trim and doors, use a smaller coverage estimate because they often need more paint per square metre. Always round up to the next available tin size. For 6.4 litres, buy 7 litres or two 4-litre tins.
Adjust for surface and colour changes
Porous or bare surfaces absorb more paint. If you are painting new plaster or going from a dark colour to a light one, you may need an extra coat. In these cases, add 20–30% to your total. If you are using a paint and primer in one, check the tin for recommended coats. For wallpaper, you do not need paint, but if you are painting over wallpaper, ensure it is sealed and sized first.
Use a paint coverage calculator for accuracy
Many paint brands offer an online paint coverage calculator. You enter room dimensions, number of coats, and door/window counts. It then tells you how many litres to buy. This is helpful for irregular rooms. If you prefer to calculate manually, use the method above. Always keep a small amount of leftover paint for touch-ups.
Step-by-step paint quantity guide
- Measure each wall: Use a tape measure to record the length and height of every wall. Multiply length by height for each wall and add them together. Common mistake: measuring floor area instead of wall area. Always use wall dimensions.
- Subtract doors and windows: Measure the height and width of each door and window. Multiply to get their area, then subtract from the total wall area. Checkpoint: if you skip this, you will overbuy paint by 10–15%.
- Find the coverage rate: Look on the paint tin or product page for the coverage rate in square metres per litre. This is usually between 10 and 14 m² per litre. If the rate is missing, assume 10 m² per litre for a safer estimate.
- Divide area by coverage: Divide your paintable wall area by the coverage rate. This gives litres per coat. Multiply by the number of coats you plan to apply. Common mistake: forgetting a second coat. Most colour changes need two coats.
- Round up and buy: Round your total litres up to the nearest tin size. If you are between sizes, buy the larger tin or an extra small tin for touch-ups. Checkpoint: keep at least 0.5 litres for future repairs.
Products that help you plan
- Blue 14: Happy-go-lucky Blue 14 is a light and cool blue paint that takes sky blue and covers it with a soothing layer of soft white cloudiness. Available in matt and eggshell finish. Matt and eggshell finishes have different coverage rates. Check the tin for the exact figure before you calculate litres.
- Diamond 01: Taken straight from an 19th century fabric design, this pink stripe wallpaper is too gorgeous to be lost. The diamonds and stripes create structure, while the earthy red, soft pink, and easygoing white add warmth and playfulness to Diamond 01. Available in a paste-the-wall roll and sample format. If you are wallpapering one wall, you do not need to paint it. This can reduce your paint quantity by one wall's area.
