More is not always better and less might not be either. See some examples below but ask a professional to determine what’s best!
Painting with the same color of paint
If the walls in a room are currently painted Ivory and you paint them with Ivory again, one coat should be sufficient. However, if the “new” paint has been stored away in the garage for 10 years or has become weathered, it might not have the coating power of brand new paint.
Assuming you’ve cleaned any dust and dirt from the walls beforehand and you use good brush and roller techniques, a single coat of same-color paint should be fine – unless the paint currently on the walls is stained or fading. In this case, you’ll probably need a primer coat.
Painting dark over light
Accurately estimating the number of coats you’ll need if you’re going from one color to another can be tricky. Theoretically, when painting a dark color over a light color, a single coat is all you need. But this isn’t always the case.
Some paint shades – for example pastels, and even some heavier colors like deep red – are low-hide colors. This means they don’t hide previous paint colors as well as other shades do, even when the previous colors are of a lighter tint. Two coats of paint are often necessary when using low-hide colors.
Also, custom-mixed colors and lower-grade paints won’t cover as well as factory-mixed paints, regardless of what shade you’re trying to hide.
Painting light over dark
Obviously when painting a light color, say a creamy yellow, over something like a rich mahogany, a single coat isn’t going to do the job. You might paint four coats, and still that creamy yellow looks polluted. In this case, you can save time and money by applying a tinted primer before the new paint.
There are many types of primer, but all of them are engineered to neutrally block a current color and provide a surface that will allow the new paint to fully attach and cover. Before selecting a primer, talk with a professional painter or an experienced paint store staff member.
As you can see, various factors affect the number of coats of paint you’ll need for most painting projects. By gaining a little knowledge about paint-coverage principles you’ll end up with a better, more economical outcome.