Two coats. That's the honest answer for the vast majority of interior work, and any decorator telling you one coat will do is either using a tinted primer underneath or setting you up for disappointment.
Here's why. The first coat does the covering and the second evens out the colour and sheen — paint dries to a consistent finish only when it's laid over itself, not over patchy substrate. Skip the second coat and you'll see flashing, roller lines and uneven depth, especially in raking light. Those "one coat" claims on the tin are marketing; they assume ideal conditions you rarely have.
When you need three coats:
- Strong, saturated colours — deep reds, dark greens, intense blues. Pigment-heavy shades like Farrow & Ball Eating Room Red, Hague Blue or Studio Green often want a third coat to look properly solid. A tinted grey undercoat (most brands offer a matched primer) cuts this down.
- Going light over dark — covering a dark wall with something like F&B Pointing or Strong White will fight you. Prime with a white or grey first.
- Bare plaster — always a thinned mist coat first (roughly 70/30 paint to water for most emulsions), then two full coats on top. The mist coat is your primer here.
- Patchy repairs and stains — spot-prime with Zinsser BIN or Cover Stain before your topcoats, or the stain bleeds through every coat you put on.
The big variable is colour, not brand. A well-pigmented paint like Little Greene Intelligent Matt or Mylands covers beautifully in two; budget trade emulsions in a deep shade can need three regardless. Coverage figures on the tin (usually 12–16 m² per litre) are per coat — double them for your actual paint order, and add a bit for waste.
Practical tip: do your cutting-in and rolling coat-by-coat across the whole wall, never wall-by-wall. And let each coat dry fully — touch-dry isn't recoat-ready. Rushing the second coat lifts the first.