How much paint does a room need? Eight worked examples

How these examples were produced

The dimensions below are sample values chosen to represent everyday rooms; your own measurements will give different figures. Everything else, however, is not written by hand: each result comes from the site's calculation engine, with the same data as the calculator. Coverage rates are category averages, not the figures of a specific brand.

Each table follows the order of the calculation: gross wall area, unpainted areas deducted, actual area, the paint's reference coverage, consumption per coat, number of coats, a 10% safety margin, then the quantity to buy and the tin combination that covers it with the least surplus, from sizes of 0.5 to 15 L. The quantity is rounded to the nearest tenth of a litre, as in the calculator. The examples are in metric units; the calculator also works in square feet and gallons.

If you are unsure about your measurements, our guide to measuring the area to paint explains the formulas used here.

1. A drywall bedroom in velvet-finish paint

A bedroom of 3.50 × 3.00 m, with a 2.50 m ceiling. The walls add up to 2 × (3.50 + 3.00) × 2.50 = 32.50 m². We deduct a 0.90 × 2.10 m door (frame included) and a 1.20 × 1.25 m window.

The two openings only take off 3.39 m², roughly a tenth of the walls: in a bedroom, the ceiling height and the perimeter are what drive the quantity. The calculator also flags a primer, recommended by default; its quantity is not included in the total, because it depends on the primer product you choose.

2. A rendered living room in matte paint

A living room of 5.20 × 4.10 m with a 2.50 m ceiling, giving 46.50 m² of wall. Three openings: a 0.90 × 2.10 m door, a 1.80 × 2.15 m French window and a 1.20 × 1.35 m window.

The suggested combination uses four tins for 9 L: it is the one that leaves the least paint unused. If you would rather have a single container, one 10 L tin also covers the need, with 1.4 L to spare. The calculator makes the first choice; the second is yours to make.

3. The ceiling of the same living room, in ceiling paint

The ceiling is calculated separately, since it gets a different paint: 5.20 × 4.10 m = 21.32 m², with no opening to deduct. The surface here is plaster.

A single 5 L tin is enough. Working out walls and ceiling together would have been a mistake: the two paints do not necessarily have the same coverage, and you would no longer know how much of each to buy.

4. A small bathroom, tiling deducted

A bathroom of 2.40 × 1.90 m with a 2.40 m ceiling: 20.64 m² of wall. We deduct the door (0.80 × 2.10 m) and, above all, the tiling, entered as an opening: a band 3.50 m long and 2.00 m high around the shower and the basin.

Here the unpainted areas make up 42% of the gross area. Forgetting to deduct the tiling would have meant buying about 59% too much paint: in small tiled rooms, measuring the unpainted areas matters most.

5. The same bathroom with an anti-condensation paint

Same walls, same actual area, but an anti-condensation paint, whose reference coverage is lower.

Coverage drops from 10 to 7 m²/L, and the quantity rises by about 43%. For the same area, the choice of paint weighs as much as the measurement. This coverage is a category average: the data sheets we consulted for this family range from 4 to 10 m²/L, as our page on paint coverage explains.

6. A fitted kitchen: units and splashback

A kitchen of 3.60 × 2.80 m with a 2.50 m ceiling: 32.00 m² of plaster walls. Besides the door (0.90 × 2.10 m) and the window (1.00 × 1.15 m), we deduct the wall units (3.60 × 0.90 m), the splashback (3.60 × 0.60 m) and the base units (3.60 × 0.90 m), which cover the wall along the full length of the worktop.

In a fitted kitchen, the unpainted areas here reach 37% of the walls. Each area is deducted only once: the splashback fills the height between the worktop and the wall units, without overlapping either. If the wall behind the units needs repainting because you are taking them down, do not deduct the units.

7. A stone wall in lime paint

A single wall 4.50 m long and 2.60 m high, with a 1.00 × 1.20 m window, painted with lime paint.

The area is modest, but the reference coverage of lime paint (8 m²/L) is lower than that of an acrylic paint. On an uneven surface such as stone, the data sheet of the product you choose remains the reference; our guide to wall types covers what each surface involves.

8. The bedroom from example 1 in one-coat paint

A one-coat paint is designed to cover in a single coat on a sound, prepared surface. The calculator still allows for two coats, as a precaution, and also shows the quantity needed for a single coat.

In a single coat, the quantity to buy falls to 3.2 L, covered by 1 × 2.5 L + 1 × 1.0 L. The two-coat quantity is therefore roughly double: it is the actual state of the surface, not the label on the tin, that will decide whether the second coat is needed.

What these examples teach

• A rule of thumb. With a coverage of 10 m²/L, two coats and a 10% margin, you need about 0.22 L of paint per square metre of actual area (2 × 0.1 × 1.1). Useful for checking a result, never for replacing the calculation.
• Unpainted areas matter most in small rooms. In the bedroom they take off about a tenth of the walls; in the tiled bathroom, more than 40%.
• Coverage weighs as much as area. Going from a paint at 10 m²/L to one at 7 m²/L raises the quantity by about 43%.
• Primer is planned separately. It is flagged, but its quantity depends on the primer product and its data sheet.
• The tin combination is a starting point. It minimises surplus; you may prefer fewer tins, as long as the total covers the need.

To get the result for your own room, open the calculator with your measurements. Its result shows the same quantities as these tables, with the same rounding: actual area, coverage, coats, consumption per coat, quantity and tins.