One litre of paint never goes as far as the tin promises – or does it? In practice, consumption depends heavily on the surface, the number of coats and the paint's coverage rate. Buy too little and you risk a visible colour difference between two purchase batches. Buy too much and you end up with leftover paint that dries out. The paint calculator gives you the exact number of litres for your surface – broken down by coats and including a 10% safety buffer.
Step by Step: How to Use the Paint Calculator
- Calculate the area: Measure the surface to be painted in square meters. For a room: wall perimeter × height, minus doors and windows.
- Enter the number of coats: Fresh plaster or dark undercoats usually need 2 coats. White over white often needs only 1 coat.
- Enter the coverage rate: The coverage rate is printed on the tin, e.g. "approx. 10 m²/L". Typical values: wall paint 6–8 m²/L, wood stain 8–12 m²/L, primer 10–15 m²/L.
- Run the calculation: Formula: (area × coats) ÷ coverage rate = litres required.
- Choose tin size: Select the right tin: 1 L, 2.5 L, 5 L or 10 L – it's usually cheaper to buy the next size up, since larger tins cost less per litre.
Practical Examples
Example 1 – Repainting a living room: Wall area 35 m², 2 coats, wall paint with 7 m²/L coverage. Requirement: (35 × 2) ÷ 7 = 10 litres. With a 10% buffer: 11 litres. Buy 2 × 5-litre tins or 1 × 10-litre tin.
Example 2 – Staining a garden fence: Fence area 18 m² (both sides included), 1 coat, wood stain with 10 m²/L. Requirement: 18 ÷ 10 = 1.8 litres. With 10% buffer: 2 litres. A 2.5-litre tin is more than sufficient.
Example 3 – Priming a ceiling: Room ceiling 16 m², 1 coat of deep primer (coverage 12 m²/L). Requirement: 16 ÷ 12 = 1.33 litres. A 2.5-litre tin is the smallest practical size and leaves enough for touch-ups.
Paint Calculator: How Much Paint Do I Need?
Formula: area (m²) × number of coats ÷ coverage rate (m²/L) = litres. Coverage rates: wall paint 6–8 m²/L, wood stain 8–12 m²/L, primer 10–15 m²/L.
Frequently Asked Questions (FAQ)
- Why does actual consumption differ from the stated coverage rate?
- The coverage rate on the tin assumes a smooth, moderately absorbent surface with a single coat at a standard application thickness. Rough walls (woodchip wallpaper, render), highly absorbent surfaces (aerated concrete, raw plugs) or heavier application increase consumption by 20–40%. In such cases, use a pessimistic (low) coverage rate in your calculation.
- Do I need to include the ceiling and floor in the room area?
- Only if you're painting them! For wall paint, calculate wall surfaces only. Ceilings often need a separate ceiling paint (white, less pigment) with different coverage figures. Floors require specialist floor paint.
- Can I buy more of the same batch later?
- With branded paints mixed to a formula, buying more is possible – but batch differences can cause slight colour variations that are invisible when wet but show up after drying. Always mix all tins thoroughly before painting, and open a second tin only after the first is exhausted.
