Paint Calculator (South Africa)

Work out your wall area first, the room's perimeter (twice the length plus the width) multiplied by the wall height, then subtract the area of your doors and windows, and multiply by the number of coats. As a worked example, a 4.0m by 3.5m room with 2.6m walls, one door and one window, comes to roughly 36.4 m² of net wall area, needing about 7.3 litres for two coats of a standard sheen paint at 10 m² per litre. The calculator above does this maths for your own room and adds a ceiling, extra walls, primer and cost on top.

Two coats is the standard minimum for almost any wall, one coat nearly always leaves patchy, uneven colour, even from a premium paint. You need a third coat if you are making a big colour change, painting a light wall a dark colour or the other way round, or if the wall is exterior and in a coastal or high-humidity area, where the extra coat adds durability against damp and salt air. A new or bare plaster wall does not need an extra topcoat, but it does need a primer coat first, see the next question. The calculator above works this recommendation out from your own answers and shows the reasoning, you can still override it if you want more or fewer coats.

Yes, if the surface is new or bare plaster, brick, or freshly skimmed drywall that has never been painted. A primer seals the surface so it does not drink up your expensive topcoat unevenly, and gives the topcoat colour something consistent to grip and cover. A plaster primer typically covers around 8.8 m² per litre in one coat, noticeably less than a topcoat, since it soaks into a porous surface. You generally do not need a primer over a wall that is already painted and in good condition, unless you are covering a very dark colour with a much lighter one, or a slick, glossy previous finish that a new coat will not grip well.

It depends heavily on the paint and the surface. South African paint technical data sheets put a smooth, previously painted wall at roughly 10 to 12 m² per litre per coat for a standard interior sheen paint, dropping to around 6 to 8 m² per litre on new, bare, absorbent plaster. Exterior textured paints cover far less, a popular South African textured exterior coating's own data sheet lists a theoretical spread rate of only around 5 m² per litre, since the fine texture uses noticeably more product than a smooth interior wall. The calculator above applies the right rate for your surface and paint type automatically rather than using one generic figure for everything.

South African paint is sold in 1 litre, 5 litre and 20 litre tins, 10 litre is not a standard retail size here despite showing up in some generic online calculators. The 20 litre tin works out noticeably cheaper per litre than the 5 litre, which in turn is cheaper per litre than the 1 litre, so for a large job it is usually worth buying one 20 litre tin over four separate 5 litre ones even if you do not need every last drop. The calculator above works out the cheapest combination of the three sizes for the exact number of litres you need, and shows how much spare paint you are left with for touch-ups.

It depends on the room size, the paint quality, and how many coats you need. As a July 2026 reference point, that same 4.0m by 3.5m example room above needs about 7.3 litres for two coats of a mid-range standard sheen product, which works out to R473 of paint by the litre, or R650 once you round that up to whole tins from the shelf, 2 x 5L in this example, before you add a primer coat, a ceiling, or the cost of brushes, rollers, masking tape and filler. Premium interior paints and textured exterior coatings cost considerably more per litre but often need a slightly thicker film per coat, so the per-room difference is usually smaller than the per-litre price gap suggests. The calculator above gives you a total cost estimate from your own room size and prices, editable if your quote differs.

Exterior paint is formulated to survive UV, rain and temperature swings that would crack or fade an interior paint within a season or two, while interior paint is formulated for washability and a smoother, often glossier finish that would not hold up outdoors. They are not interchangeable, do not use leftover interior paint on an outside wall to save money, it will fail early. A textured exterior coating also covers considerably less area per litre than a smooth interior paint, roughly 5 m² per litre against 10 to 12 m², so budget more litres and more cost for the same wall area outside than inside.

Yes, salt air and higher humidity along the South African coastline are harder on exterior paint film than an inland, drier climate, so an extra topcoat is common practice for coastal exterior work, three coats rather than the standard two. It is not usually necessary for interior walls unless the room itself is unusually damp, like an unventilated bathroom. The calculator above adds this coat automatically when you flag exterior plus coastal or high-humidity, and you can always override the coat count if your painter recommends differently for your specific property.

A ceiling's area is simply the room's floor footprint, length times width, not the wall area. Ceiling paint is usually a flat, matt finish with somewhat lower coverage than a smooth sheen wall paint, and a ceiling that has never been painted, common in a new extension, needs its own primer coat too. The calculator above has a separate ceiling option that uses the room's own length and width, with its own coat count, coverage rate and price, so it is not folded into or confused with the wall paint total.

You do not paint over a door or window, so their area needs to be subtracted from the wall area you calculate, otherwise you will overestimate your litres and overspend. Standard South African door and window sizes are roughly 0.81m by 2.03m for a door and 1.02m by 0.95m for a window, a combined deduction of roughly 2.6 m² per door-and-window pair, which adds up across a whole room or house. The calculator above uses these as sensible defaults and lets you enter your own exact sizes if your doors or windows are non-standard.

For an L-shaped room, an alcove, a garage, or any standalone extra wall like a feature wall or gable, use the "add an extra wall" option in the calculator above rather than trying to force an irregular shape into the main length and width fields. Enter the extra section's own width and height and it gets added straight into the total wall area alongside the main room's four walls, before doors and windows are subtracted.

Yes, it is worth buying a little more than the bare minimum. A small amount left over covers scuffs, nail holes and general wear touch-ups for years afterwards without needing to remember or rematch a paint code later, and colours are occasionally discontinued or reformulated. The calculator above already shows this as "spare" litres in the tin breakdown, since rounding up to whole tins nearly always leaves a bit over.

That depends heavily on whether you mean a professional painter's quote or doing it yourself. Professional painters in South Africa typically quote by the square metre of wall area for a full job including labour, surface preparation and materials, roughly R100 to R250 per m² for interior work and often somewhat more for exterior work once prep and weather-resistant paint are factored in. A typical South African three bedroom house has roughly 250 to 300 m² of interior wall area, which puts a full professional interior repaint at very roughly R25 000 to R75 000 all in, depending on the painter, prep needed and paint quality. The paint itself is a much smaller slice of that, this calculator's own numbers put the DIY paint-only cost for that same wall area, two coats of a mid-range standard sheen, at roughly R2 210 to R2 340. Labour, scaffolding or ladders, masking, filler and prep make up the rest of a professional quote, always get a few quotes rather than relying on a single average figure.

Yes. Unlike a calculator published by a specific paint brand, which is naturally built around that brand's own products and spread rates, this one is brand-neutral, you choose the paint quality tier and it applies a realistic coverage rate for that type of product, and every price is editable if your own tin's label quotes a different spread rate. That means it works whether you end up buying Plascon, Dulux, Duram, Prominent, a hardware store's own house brand, or anything else, the maths does not care which tin is on the shelf.

A little, though surface condition and colour change matter more. A flat or matte finish generally has more pigment and hides better in fewer coats, which is why ceilings and many budget interior paints are matte. A sheen, satin or gloss finish is thinner and more washable but sometimes needs an even, careful second coat to avoid patchiness, particularly in bright light where unevenness shows up more on a shinier surface. Two coats is still the right starting point for any finish, the calculator's colour-change and surface-condition questions matter more to the coat count than the finish itself does.