How much wall paint do you need? Calculate paint coverage easily (with table)

How much wall paint do you need — this question usually comes up too late, namely on a Sunday at four o'clock, when the bucket is empty and the wall is only half finished. Yet all you need for the answer is two numbers and a minute. This guide works through a real room, matches the result to the container sizes, and shows you where the usual calculation mistakes happen.

The calculation in two lines

The formula

Wall area equals the room's perimeter times the room height. Paint quantity equals area times the number of coats, divided by the coverage rate. That's really all there is to it — the rest comes down to careful measuring. Just make sure you use the same units for both figures: metres and square metres, not centimetres.

The coverage rate to calculate with

For re-box wall paints the rule is: 1 litre covers approx. 6–8 square metres per coat. If in doubt, calculate with the lower figure. On very dark, strongly coloured, or uneven surfaces, consumption can increase further.

Why you should include windows and doors in your calculation

Strictly speaking, you're allowed to subtract openings. In practice, it's rarely worth it: window and door reveals use up paint too, touch-ups do as well, and a tightly calculated bucket is the start of a visible patch. Only subtract really large areas — a floor-to-ceiling window front, for example.

One coat or two?

This decision doubles or halves your result, so make it before the calculation, not after. Two coats are the standard: they cover more reliably and give a more even finish. All container quantities in this article are therefore based on two coats.

A real room, calculated step by step

The floor plan

Take a room measuring 4 by 3.5 metres with a height of 2.50 metres. The perimeter is 15 metres, so the wall area is around 37 square metres. The ceiling adds another 14 square metres.

The amount for the walls

With two coats, that's 74 square metres of surface to paint. Divided by 6 to 8 square metres per litre, you land at around 9 to 12 litres. The 10-litre container is therefore the right basis, provided the surface absorbs normally.

The amount including the ceiling

Add the ceiling, and you get 51 square metres of area, and with two coats a good 100 square metres of surface to paint. That works out to 13 to 17 litres: a 10-litre container plus a 5-litre container. The rest goes into the cellar as a reserve.

What one container covers

2.5 litres

With two coats, this covers roughly 8–10 square metres. That's enough for a single accent wall, for the stretch of hallway between two doors, or for touch-ups after moving in. For a single coat, that works out to roughly 15–20 square metres.

5 Liter

With two coats, this covers roughly 15–20 square metres — so a small child's room, a bedroom with plenty of wardrobe space, or a mid-sized ceiling. With one coat, you'll get roughly 30–40 square metres, which in practice is mainly relevant for ceilings.

10 Liter

With two coats, you get roughly 30–40 square metres. That's the standard amount for a whole room, not counting the ceiling. All figures are deliberately given as ranges: actual consumption depends on the surface, and a range is more honest than a single number that might not hold true for your wall.

If you fall between two sizes

Round up. The extra cost of the next size up is smaller than the hassle of a reorder that costs you several working days and, in the worst case, leaves a visible line. Alternatively, combine one large container with a smaller one.

What drives consumption up

The surface

Fresh plaster and highly absorbent surfaces soak up noticeably more paint than a smooth existing coat. A primer isn't strictly necessary here, but it does ensure even drying and reduces consumption — you'll find what suits your project under Primer & Preparation.

The colour jump

Light over light is no problem. A deep blue over an old cream tone, or white over anthracite, needs more material and patience. Always plan for two full coats with changes like these.

The ceiling everyone forgets

The ceiling is the item most often missed when measuring up — yet in a typical room, it amounts to almost half a wall's worth of surface. Either factor it in from the start, or make a conscious decision to leave it out.

Tools and technique

A good roller picks up paint evenly and releases it evenly, and a roller grid doses it cleanly. What stays in the bucket or ends up on the dust sheet doesn't show up in any formula — but it's still missing from the wall.

What you need to calculate and mix

For measuring up

• A folding rule or tape measure — pacing it out is too imprecise for this kind of calculation
• A notepad with one line per wall, so you don't double-count when adding it all up
• The room height, measured once in the middle and once at the door, in case the floor is uneven

For the paint itself

• Your shade from our colours, in the right quantity and your chosen finish
• 10 Liter Leereimer, if you want to combine two containers into a single batch
• Rührholz - 30,5x3 cm, because paint always needs stirring after delivery

For what's left in the bucket

• A container that seals cleanly for your reserve
• A strip of tape noting the room, colour name and date — a year from now, you won't remember otherwise

Measuring up, wall by wall

1. Measure wall by wall

Measure each wall's length individually and write it down. In rooms with sloped ceilings or awkward angles, break the surface down into rectangles and triangles — a triangle is base times height, divided by two.

2. Multiply by the room height

Calculate each wall separately and add up the results. This is more reliable than working from the total perimeter as soon as there's a bay, an alcove or a jutting section in the room.

3. Decide on the ceiling

Length times width gives you the ceiling area. Now is the moment to decide — not halfway through the project, once the paint is already sitting there. If you're painting the ceiling too, do it first and the walls afterwards: ceiling splatter on a freshly painted wall costs you an entire second coat.

From area to order

4. Decide on the number of coats

Two coats is the standard case and the basis for all the figures above. Only with a very subtle colour change on a smooth surface can you get away with one.

5. Match to container size

Compare your area with the ranges above and round up. Combining two containers is completely normal — 10 plus 5 Liter cover a room including the ceiling. If you're unsure, Anna, re-box's digital colour consultant, can help you with quantity and finish.

6. Order in good time

Every shade is mixed individually after ordering, including the white tones. Delivery takes 3–5 working days from receipt of payment, shipped within Germany. If you'd rather have everything in one package, take a look at our renovation boxes.

The three calculation mistakes that cost you money

Cutting it too close

Order exactly what you calculated, and you've ordered too little. One extra splash, a reveal you didn't account for, a wall that absorbs more — and you're missing exactly the half litre that would have finished the job. Plan for around ten percent extra as a reserve.

Ordered twice instead of once

Paint from two separate mixes can turn out very slightly different. If you notice this halfway across a wall, you'll see it for good. So for one continuous surface: one order, one mix — combine them in a bucket beforehand if needed.

Skipping the test patch

In the end, it's not the wrong quantity that's annoying, but the wrong shade. Custom-mixed paints are excluded from returns and exchanges. Take a look at the shade beforehand — with the colour sample cards or via the Colour Finder.

Frequently Asked Questions About Paint Usage

Quantity and Area

How much paint do you need for 20 square metres of wall?
For one coat, around 2,5 to 3,5 litres; for two coats, double that — so a 5-litre container. On absorbent or fresh plaster, go with the higher figure.

Is one coat enough?
On an even, light-coloured surface with only a small colour change, often yes. For bold shades, fresh plaster, or a switch from dark to light, plan for two coats — they also look calmer.

How do you calculate a sloped ceiling?
Break the area down into simple shapes: rectangles are measured as length times height, triangles as base times height divided by two. Add up the individual areas, then carry on calculating as you would for a straight wall.

Ordering, Storing, Touching Up

What do you do with leftover paint?
Store it well sealed, cool, and frost-free — that way you'll have a reserve from the same mix for drill holes and furniture scuffs. Label the tin with the room and colour name; it saves you the guesswork later.

Can you return paint you've over-ordered?
No, custom-mixed paints are excluded from returns and exchanges, because they're only mixed after you place your order. Specially marked white goods can be returned to re-box undamaged and in their original packaging. That's the second good reason to calculate the quantity carefully beforehand.

Can you also get a shade that isn't in the range?
Yes, via Custom Shade – Mixed to Order. It's tinted based on re-box base one (matt), the tint base for all colours. To see how this works out in a real project, check out Painting Your Kitchen Instead of Buying New: Guide, Costs, and the Right Paint.