Buying floor paint without working out the coverage first is a gamble. Order too little and you are stuck mid-job waiting on a fresh tin, often from a different batch with a slightly different shade. Order too much and you have wasted money on paint that dries out in the garage. The good news is that working out how much floor paint you need is straightforward once you know the surface area and the coverage rate of your chosen product.
This guide walks you through the simple formula, gives you worked examples, and explains the factors that quietly change how far a tin actually goes. If you want the bigger picture on choosing a coating first, our guide to the Best Floor Paints for Concrete, Garage and Industrial Floors compares the options by surface and traffic level.
How floor paint coverage works
Every floor paint has a coverage rate, usually shown on the tin as the number of square metres one litre covers in a single coat. It is often written as a spreading rate, for example 6 to 10 square metres per litre. Spreading rate is a standard measure used across the UK coatings industry, and the British Coatings Federation has more general background on paints and coatings if you want to read around the subject.
That range matters. The higher figure assumes a smooth, sealed, non-porous surface. The lower figure is closer to what you will actually get on bare or textured concrete that drinks in the first coat. Always plan around the lower end of the range so you do not come up short.
As a rough guide only (always check your specific product):
|
Surface condition |
Typical coverage per litre, per coat |
|
Smooth, previously sealed or painted |
8–10 m² |
|
Sound but slightly porous concrete |
6–8 m² |
|
Bare, porous or textured concrete (first coat) |
4–6 m² |
Step 1: Measure your floor area
Coverage all starts with area. For a simple rectangular floor, measure the length and the width in metres and multiply them together.
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Length x width = floor area in square metres (m²)
For an L-shaped or irregular space, split it into rectangles, work out each one, and add them together. If you are painting steps, a ramp or skirting-style edges, add a little extra for those too. It is also worth measuring the floor properly if you are following our step-by-step on how to paint a concrete garage floor, since good measurements make the whole job run smoothly.
Step 2: Use the coverage formula
Once you know your area, the calculation is simple:
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Paint needed (litres) = floor area (m²) ÷ coverage rate (m² per litre) x number of coats
So for a floor that needs two coats, you work out the litres for one coat and then double it. Remember to base the coverage rate on the realistic figure for your surface, not the best-case number.
Worked examples
Single garage (about 15 m²), two coats, coverage 6 m² per litre: 15 ÷ 6 = 2.5 litres per coat, x 2 coats = 5 litres.
Double garage (about 30 m²), two coats, coverage 6 m² per litre: 30 ÷ 6 = 5 litres per coat, x 2 coats = 10 litres.
Small workshop (about 20 m²), two coats, coverage 8 m² per litre on a sound floor: 20 ÷ 8 = 2.5 litres per coat, x 2 coats = 5 litres.
In each case, round up to the nearest tin size and add a little extra, which we cover below.
What changes how much paint you need
Several things affect how far your paint stretches, and most of them push the figure up rather than down:
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Surface porosity. Bare, dry or old concrete soaks up far more on the first coat than a sealed surface. This is the single biggest factor.
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Surface texture. Rough, broomed or worn concrete has more surface area than a smooth slab, so it uses more paint.
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Number of coats. Most floors need two coats for durability and an even finish. Some very porous or dark-to-light colour changes need three.
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Application method. Rollers and brushes give good control. Spraying can be faster but often uses more paint through overspray.
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Colour change. Going from a dark floor to a light colour, or vice versa, can need an extra coat to cover properly.
Do not forget the primer
Your topcoat is not the only thing you need to buy. Bare and porous concrete should be sealed with a concrete primer first, which has its own separate coverage rate to calculate. Priming also makes your topcoat go further, because it stops the concrete drinking in that expensive first coat of colour. To understand why this step is so important, see our guide to the role of primers and undercoats.
How many coats do you actually need
For most floors, plan on two coats of topcoat over a primed surface. Two thin, even coats give a tougher, longer-lasting finish than one thick one. Resist the urge to load the paint on to save a coat, because coats that are too thick trap solvent, cure poorly and are a common cause of floor paint peeling or flaking later on.
Between coats, respect the recoat time on the tin. Drying and curing are not the same thing, and recoating too soon causes problems, as our guide on drying time vs curing time explains.
Choosing a paint changes the maths
Different products have different spreading rates, so the coating you choose affects how many litres you buy. A hard-wearing epoxy or polyurethane will behave differently from a quick-drying paint, and each has its own coverage on the tin. Our epoxy vs polyurethane floor coatings guide compares the two for tougher floors, and you can browse the full range in our floor paints and polyurethane and epoxy floor paints collections. If you need a fast turnaround, a quick-drying floor paint is worth a look, and if you plan to add grip, remember an anti-slip additive or paint can slightly change coverage too. For workplace floors in particular, the HSE's guidance on flooring and slip resistance is a useful reference on getting the surface right.
Tips to avoid running out
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Always buy around 10% more than the calculation suggests, to allow for porous patches, edges and touch-ups.
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Buy all your paint in one go so it comes from the same batch and the colour matches exactly.
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Base your sums on the lower coverage figure for your surface, not the best case.
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Keep a small amount back, sealed, for future repairs and touch-ups.
If you do end up with usable paint you are never going to need, it does not have to go to waste. A reuse network such as Community RePaint collects leftover paint and redistributes it to community groups and households across the UK.
Work out your area, apply the formula, factor in porosity and coats, and you will buy the right amount first time, with just enough spare to finish the job neatly.
