Key takeaways
- Surface area divided by the product’s coverage.
- A coat of interior paint often covers 33 to 37 m² per 3.78 L, depending on the product.
- Round up and keep a little paint for touch-ups.
Step 1: measure the surface
Multiply the height by the width of each wall and add the results. Then subtract the space taken by large openings such as doors and big windows. Add the ceiling if you are painting it.
Step 2: know the coverage
- Interior paint: about 33 to 37 m² (350 to 400 sq ft) per 3.78 L.
- Primer: about 19 to 28 m² (200 to 300 sq ft) per 3.78 L.
- Exterior paint: about 23 to 37 m² (250 to 400 sq ft) per 3.78 L.
- The exact coverage is printed on the product label.
These numbers are theoretical: wall texture, application method and paint left on the tools reduce real coverage.
Step 3: divide and round up
Divide the area by the coverage. For example, 90 m² to paint with a product covering 35 m² gives about 2.6 containers of 3.78 L per coat. Count the number of coats: two are common, more for a big colour change.
Always round up: it is better to keep a little paint for touch-ups.
Why buy it all at once
A slight shade difference can exist between batches. For one continuous wall, mix the containers together before painting to even out the colour.
Frequently asked questions
- How do I calculate for a ceiling?
- Multiply the room’s length by its width. The ceiling is figured as a separate surface.
- Should primer be counted?
- Yes, if it is needed. Primer has its own coverage, usually lower than finish paint.
