How it is sold
By the tin, in litres across Europe and in US gallons in the United States. A US gallon is 3.785 litres, not the 4.546 of the old imperial gallon — a distinction that still catches people reading older coverage tables.
| Tin | Typical use |
|---|---|
| 1 L / 1 quart | Touch-ups, a single feature wall, testing a colour |
| 2.5 L | One average room, one coat, or a ceiling |
| 5 L | The standard size: one room, two coats, with a little spare |
| 10 L / 1 gal | Whole flats, stairwells, trade work |
Larger tins are almost always cheaper per litre, which is why the round-up step of any estimate is worth doing properly rather than in your head at the shelf. Two 5 L tins plus a 2.5 L often beats three 5 L tins by the price of a roller set.
Finishes, and what each costs you in coverage
- Matt
- No sheen, hides surface defects best, and the usual choice for ceilings and adult bedrooms. Marks easily and does not like being scrubbed. Coverage is generally the best of the family, around 12-14 m² per litre on a sealed wall.
- Washable matt / durable matt
- Matt appearance with a tougher binder, for hallways and children's rooms. Coverage drops a little, typically 10-12 m² per litre, and the price rises noticeably.
- Eggshell / silk
- A low sheen that wipes clean, common in kitchens and bathrooms. It reflects light, so it shows every ripple in the plaster — the surface has to be good. Around 10-12 m² per litre.
- Satin and gloss on woodwork
- A different product entirely, for trim and doors. Coverage looks high on the tin because the surfaces are small, but cutting in uses far more per square metre than rolling a wall.
The pattern worth remembering: durability and washability cost coverage. Choosing a hard-wearing finish for a hallway is usually right, but budget the extra litres rather than being surprised by them.
The numbers that drive a calculation
Only three figures on the tin matter to a quantity estimate, and one of them is not printed at all.
- Coverage, or spreading rate
- Square metres per litre per coat. Measured on a smooth, sealed, non-absorbent panel, so treat the printed figure as an upper bound. New plaster, filler repairs and any texture will take more.
- Tin size
- Decides the rounding, which on a small job dominates the estimate entirely. A result of 5.2 litres costs the same as 7.5 if the shelf holds 2.5 L tins.
- Number of coats — not on the tin
- Two is the honest default over an existing colour. One works only for a refresh in the same shade; a strong colour or a light finish over a dark base often needs three. This is the figure that moves an estimate most, because an extra coat costs the whole area again.
litres = area × coats ÷ coverage × (1 + waste)
Choosing
- Ceilings: matt, brilliant white, and a dedicated ceiling paint if you want less spatter.
- Bedrooms and living rooms: matt for looks, durable matt if there are children or pets.
- Hallways and stairs: durable matt or eggshell — these walls get touched constantly.
- Kitchens and bathrooms: a moisture-resistant eggshell or a specific bathroom paint. Ordinary matt will not survive the condensation.
- Bare plaster: a thinned mist coat first, or a purpose-made sealer. This is not optional.
- A strong colour change: ask for a tinted base coat. It is cheaper than the two extra finish coats it replaces.
Coverage ranges here are compiled from typical manufacturer datasheets for interior emulsion. The figure on your own tin always wins, and a real wall rarely reaches the laboratory number.