Helpful video reference. The video above is "How Much Paint Do You NEED? // How To Measure For Buying Paint" from Paint Your Home Now. It is a practical walk-through of the technique, worth watching for the hand movement rather than just reading about it.
Measure the walls, not the floor
Measure the length of each wall and the height from skirting to ceiling. Multiply length by height for each wall, then add the results together. A room of four metres by three metres with a 2.4 metre ceiling has roughly 33.6 square metres of wall.
Do not use the floor area. Two rooms with the same floor space can have very different wall areas depending on ceiling height and how many alcoves there are.
Take off the openings, but not too generously
Subtract the area of doors and windows. A standard internal door is a little under 1.7 square metres. Windows vary, so measure them. Leave the chimney breast in, because the extra faces and returns all take paint.
If you are only taking off one or two small windows, it is usually safer to ignore them and keep the spare paint for touch-ups.
Read the coverage on the tin
Every tin states a coverage figure, normally in square metres per litre for one coat. Divide your wall area by that figure, then multiply by the number of coats you plan to apply. Two coats is the sensible minimum for a lasting finish on walls.
Treat the printed figure as the best case. It assumes a smooth, sealed, previously painted surface. Rougher or more absorbent walls will drink more.
Add for the surface and the colour change
New plaster or freshly filled areas soak up the first coat, so a mist coat of thinned emulsion uses extra before the real coats go on. A deep or dark existing colour under a pale new one may need a third coat as well.
As a rule of thumb, add around 10 percent to your sum for a normal wall and more for bare or heavily patched plaster.
Buy once, and keep a record
Buy all the paint for a room in one go and check the batch numbers match, or mix the tins together in a bucket so any slight variation evens out. Write the colour name, finish and room on the lid before you store the leftovers.
What this means in Herne Bay
Seafront terraces in Herne Bay often have tall Victorian ceilings, which push the wall area up faster than the floor plan suggests, so measure the height rather than assuming 2.4 metres. The 1930s semis towards Beltinge and Hampton tend to have more standard heights, but bay windows add awkward returns that use more paint to cut in around.
Common mistakes to avoid
- Calculating from floor area instead of wall area, which can leave you well short in a tall room.
- Forgetting that bare plaster or a strong colour change needs extra paint for the first coat.
- Buying a second tin later from a different batch and finding a slight difference in shade across one wall.
Quick answers
Do I need to include the ceiling in the same calculation?
No. Work the ceiling out separately using length times width, and use ceiling paint or matt emulsion with its own coverage figure.
Is it fine to keep leftover paint?
Yes, if the lid is sealed well and it is kept somewhere frost free. A small amount is worth keeping for touch-ups, labelled with the room and colour.
Prefer we do it?
Room painting from £325, standard trade paint and labour included. See our price guide, our interior decorating page or get a fixed quote.