Solve backwards
How much new plaster will my mist coat paint cover?
- 1 galThe example worked below
- Mist Coat CalculatorEvery figure is its own
You have
How much mist coat paint?
That is 1 gal(3.8 L). Worked by the Mist Coat Calculator at the settings below.
The settings it uses
- Spread rate of the mix
- 400 ft²/gal
- Water added, as a share of the paint
- 20
- Mist coats
- 1
What it will do
480 sq ft of new plaster
44.6 m²
One room. Enough for the walls of a room about 15 × 15 ft with 8 ft walls.
Or several. About 1 room of the size the Mist Coat Calculator opens on: the walls of a room about 13.4 × 13.4 ft with 8 ft walls.
Check it forwards
- Area of new plaster
- 480 sq ft
- It asks for
- 1 gal
- You have
- 1 gal
The Mist Coat Calculator asks for 1 gal at that size.
If you had more, or less
Around your amount
Each worked by the Mist Coat Calculator at the same settings.
Half
0.5 gal
240 sq ft
the walls of a room about 7.5 × 7.5 ft with 8 ft walls
Yours
1 gal
480 sq ft
the walls of a room about 15 × 15 ft with 8 ft walls
Half as much again
1.5 gal
720 sq ft
the walls of a room about 22.5 × 22.5 ft with 8 ft walls
Double
2 gal
960 sq ft
the walls of a room about 30 × 30 ft with 8 ft walls
Common amounts
What each amount of mist coat paint covers
The sizes it is usually sold in, each worked by the Mist Coat Calculator at the settings above.
| You have | It covers | As one room | Average rooms |
|---|---|---|---|
| 1 gal(3.8 L) | 480 sq ft(44.6 m²) | the walls of a room about 15 × 15 ft with 8 ft walls | 1 |
| 2 gal(7.6 L) | 960 sq ft(89.2 m²) | the walls of a room about 30 × 30 ft with 8 ft walls | 2 |
| 5 gal(18.9 L) | 2,400 sq ft(223 m²) | the walls of a room about 75 × 75 ft with 8 ft walls | 5 |
The water stretches the paint, not the rate
At the calculator's 20 per cent, every five parts of paint take one part of water and make six parts of mix — the tin's wording, read as a share of the paint. So a litre of emulsion makes 1.2 litres of mist coat, and the plaster it covers is set by the mix. Put zero for paints sold ready for new plaster that must not be thinned.
New plaster drinks more than the tin says
Tins commonly rate contract matt at about 12 to 14 m² per litre on a sealed wall; on new plaster the thinned mix gets nearer the calculator's 10, and on a very thirsty skim less again. The first wall is the real measurement: if it takes noticeably more, use what it actually took for the rest of the room.
Only the new plaster counts
Old, sound painted surfaces do not take a mist coat, so measure just the new plaster in a room that is part old and part new. Mist coating an already sealed surface does nothing useful and leaves a thin, patchy film for the next coat to cover. And the plaster must be dry right through first — a skim commonly takes a week or more.
How the answer is worked
Nothing here is a second formula. The Mist Coat Calculator runs forwards — a size in, a quantity out — and this page grows its own starting room in proportion until the quantity it asks for is what you have. Where it rounds up to whole containers, the answer is the largest size before the next one would be needed.
Where the calculator adds an allowance for cuts or breakage when you order, the same allowance comes off here, because it is the same calculator: a stack you already own finishes less than its face value. Where it adds none, neither does this page — the settings beside the answer say which.
Mist Coat Calculator
runs it forwardsPaint and water for a mist coat on new plaster — the thinned first coat, split into what you buy and what comes out of the tap.
Work out what to buy insteadSolve backwards
Other things you might already have
How much wall will my paint cover?
Wall paint, worked by the Paint Calculator.
How many ceilings will my paint cover?
Ceiling paint, worked by the Ceiling Paint Calculator.
How much wall will my primer cover?
Primer, worked by the Paint Primer Calculator.
How much siding will my exterior paint cover?
Exterior paint, worked by the Exterior Paint Calculator.
How big a deck will my stain cover?
Deck stain, worked by the Deck Stain Calculator.
How much fence will my stain cover?
Fence stain, worked by the Wood Fence Stain Calculator.
Solve backwards
Start from what is already in the yard
Paint, sheets, rolls, bags and pieces, each read the other way by the calculator that orders it.
The calculator's own figures
Nothing is estimated twice: the page runs the same calculator you would order with.
The largest size that fits
Where a calculator rounds up to whole containers, the answer stops before the next one.
Both unit systems
Gallons and litres, square feet and square metres, side by side.
Frequently asked questions
- How much new plaster does 1 gal of mist coat paint cover?
- At the Mist Coat Calculator's own settings, 480 sq ft (44.6 m²) — the walls of a room about 15 × 15 ft with 8 ft walls. That is about 1 room of the size the calculator opens on: the walls of a room about 13.4 × 13.4 ft with 8 ft walls. Every figure follows the settings, which you can change in the calculator.
- How much new plaster does 5 L of mist coat paint cover?
- At the Mist Coat Calculator's own settings, 60 m² (646 sq ft) — the walls of a room about 6.3 × 6.3 m with 2.4 m walls. That is about 1 room of the size the calculator opens on: the walls of a room about 4.2 × 4.2 m with 2.4 m walls. Every figure follows the settings, which you can change in the calculator.
- How much water do I add to paint for a mist coat?
- Follow the tin. Most contract and vinyl matt emulsions are thinned 10 to 20 per cent for a mist coat, read as a share of the paint: 20 per cent is one part water to five parts paint. Some paints are made for new plaster and must not be thinned at all.
- Do I need one or two mist coats?
- One is normal. Where the first dries back patchy and still thirsty-looking, the plaster has taken it all and a second is worth doing. Two thin mist coats seal better than one heavy one, which starts to behave like the unthinned coat the exercise is meant to avoid.
- Is a mist coat the same as a primer?
- No. A mist coat seals the suction of new plaster so the paint over it keys and dries evenly. It does not block stains, cover a strong existing colour, or prepare a glossy or powdery surface — those need a primer chosen for the job.