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How much paint do I need? Multiply the area in square metres by the number of coats, then divide by the product’s coverage rate in square metres per litre: litres needed = area × coats ÷ coverage. For example, 30 m² painted with two coats of Dulux Matt at up to 14 m² per litre works out at 4.29 litres, so a 5L tin is the practical purchase. Coverage figures are normally maximum or theoretical rates; porous surfaces, rough plaster, application conditions and major colour changes can increase consumption.
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How do I calculate litres of Dulux paint per square metre?
The reliable method is to calculate total coated area first, then divide by the coverage printed for the exact product. Dulux’s calculator uses the same relationship: surface area divided by coverage per litre, multiplied by the number of coats.
Litres needed = surface area (m²) × number of coats ÷ coverage (m²/litre)
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- Measure each wall, ceiling or other surface and calculate its area in square metres.
- Add the areas that will receive the same paint.
- Subtract large openings such as doors or windows if you have measured them separately; leave small openings in the total to provide a sensible waste allowance.
- Multiply the area by the required number of coats.
- Divide by the product’s stated square metres per litre.
- Round up to the next available tin size rather than buying the exact decimal quantity.
Coverage is quoted per coat. A two-coat specification therefore doubles the volume calculated for one coat before you round up. A product advertised as one coat should be calculated with one coat only when the surface and colour meet that product’s conditions.
How should I measure the area before buying paint?
Measure in metres and use the shape of each surface. For a rectangular wall, multiply width by height. For a ceiling, multiply length by width. Record each wall separately when rooms contain different heights, alcoves or chimney breasts, then add the results.
Walls with openings
Measure doors and windows as rectangles and subtract their areas when they occupy a substantial part of the wall. If you omit small openings, the extra paint helps cover edges, reveals and normal application loss. Keep a written total for each colour and finish so that rooms requiring different products are not combined accidentally.
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Irregular or textured surfaces
Use the measured flat area as your starting point, but expect a textured, heavily patched or porous surface to consume more than the headline rate. The technical sheets describe practical spreading as dependent on the substrate, application method, application conditions and the complete paint system.
What coverage do current Dulux products provide?
The figures below are the published rates associated with the named products. “Up to” and theoretical values are not guarantees of site consumption, and the product tin or current product page should be checked before purchase because claims and pack availability can change.
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| Product | Published coverage | Coat guidance | Finish and use | Listed pack sizes |
|---|---|---|---|---|
| Dulux Matt | Up to 14 m²/litre (Dulux product page; publication year not stated, accessed 2026) | Dulux lists two coats | Matt for interior walls and ceilings | 2.5L, 3L, 5L, 6L, 7L, 7.5L and 10L |
| Dulux Simply Refresh One Coat Matt | Up to 10 m²/litre (Dulux product page; publication year not stated, accessed 2026) | Presented as a one-coat product | Matt interior paint where the surface is suitable for the one-coat claim | 2.5L, 5L and 10L |
| Dulux Walls & Ceilings | Matt: 11.0–8.3 m²/litre/coat; silk: 11.6–8.8 m²/litre/coat (AkzoNobel Decorative Paints technical sheet, updated September 2022) | System information specifies one primer coat plus two matt or silk topcoats on new, normal, sound surfaces | Matt or silk wall and ceiling system | Pack sizes are not stated in the cited technical sheet |
| Dulux Trade Supermatt | Up to 18 m²/litre under normal conditions (AkzoNobel/Dulux Trade technical sheet, July 2023) | Normal finishing process is two coats; significant colour changes can require more | Trade matt paint | 5L and 10L |
The retail Dulux Matt figure is a maximum rate, while the Walls & Ceilings figures are a range of theoretical coverage per coat. They should not be substituted for one another in a calculation. Use the rate for the exact tin, sheen and product line you intend to apply.
How many coats should I include in the calculation?
Include every coat that the stated system requires. Dulux Matt and Dulux Trade Supermatt both describe a normal two-coat finish, so the area is multiplied by two. Dulux Simply Refresh One Coat Matt is specifically presented as one coat, but that does not remove the need to prepare an unsuitable, stained, very porous or dramatically different-coloured surface.
New plaster and unsealed surfaces
New plaster and other porous substrates can draw paint unevenly. The Dulux Walls & Ceilings system calls for one primer coat followed by two matt or silk topcoats on new, normal, sound surfaces. If you are using that system, calculate primer and topcoat quantities separately, using the coverage stated for each product.
Major colour changes
A strong change, such as covering a deep red with a pale colour, can need an additional coat. The Dulux Trade technical information explicitly notes that significant colour changes may require extra coats. Add the extra coat to the formula rather than trying to compensate by spreading the paint thinner.
What are the exact litre calculations for common room sizes?
These examples use the published maximum or theoretical rates and show why rounding to a real pack matters. Actual consumption can be higher when conditions are difficult.
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30 m² with Dulux Matt
For a 30 m² wall area and two coats at up to 14 m²/litre: 30 × 2 ÷ 14 = 4.29 litres. A 5L tin is the next listed practical size. The calculation does not promise that 4.29 litres will finish every wall; the 14 m²/litre figure is an “up to” rate.
20 m² with Simply Refresh One Coat Matt
For 20 m² and one coat at up to 10 m²/litre: 20 × 1 ÷ 10 = 2 litres. The next available listed size is 2.5L. Use this result only when the existing surface is appropriate for a one-coat application.
40 m² with Dulux Trade Supermatt
For 40 m² and the normal two coats at up to 18 m²/litre: 40 × 2 ÷ 18 = 4.44 litres. Trade Supermatt is listed in 5L and 10L packs, making 5L the minimum listed pack for the arithmetic result. Allow more if the substrate is porous, the finish is being changed substantially or an additional coat is specified.
Using a theoretical range
If a technical sheet gives a range, calculate conservatively with the lower end when the surface is absorbent or the application is demanding. For example, a matt rate of 8.3–11.0 m²/litre/coat means the same area will require more litres at 8.3 than at 11.0. Keep the range attached to the product and substrate conditions; it is not a single guaranteed rate.
Why can actual paint use be higher than the tin’s coverage?
Coverage figures assume suitable preparation and normal application. Dulux and AkzoNobel technical information identifies several variables that alter practical spreading:
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- Substrate: porous plaster, bare masonry, filler and unsealed repairs absorb more material.
- Surface texture: rough or textured walls hold paint in their profile and expose more surface than a smooth wall.
- Application method: roller pile, brush work, spray settings and the way paint is loaded affect spreading.
- Conditions: temperature, ventilation and the condition of the surface influence how the coating behaves.
- Colour change: a large difference between old and new colours can require an additional coat, especially where hiding is difficult.
- System requirements: primer, mist coat or specified topcoats add separate material beyond a simple decorative two-coat estimate.
These factors are why a maximum rate should be treated as an optimistic starting point. Buying exactly the calculated decimal quantity leaves no allowance for edges, touch-ups or a second pass over areas that still show through.
How do I choose the right tin size and avoid running short?
Round your calculated litres upward to a pack that the product actually sells. For 4.29 litres of Dulux Matt, 5L is appropriate; for 4.44 litres of Trade Supermatt, 5L is the smallest listed pack. If the calculation is just below a pack boundary, the larger size is safer than combining an assortment that may not be tint-matched.
Check the current pack list
Dulux Matt is listed in 2.5L, 3L, 5L, 6L, 7L, 7.5L and 10L; Simply Refresh in 2.5L, 5L and 10L; Trade Supermatt in 5L and 10L. Retail availability can vary, so verify the current tin before paying. A product page’s pack list is not a substitute for checking the label on the batch you receive.
Keep batches consistent
For a continuous wall, use tins from the same colour and product specification. If several tins are needed, mix them in one clean container before rolling (often called boxing) so small batch variations are less visible. Do not mix different finishes or product lines simply because their coverage rates look similar.
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Preparation does not change the formula, but it improves the chance of approaching the stated rate and achieving even hiding.
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- Remove dust, grease and loose material, then allow the surface to dry.
- Fill cracks and holes and sand repairs so they do not absorb paint at a different rate from the surrounding wall.
- Seal or prime porous areas according to the chosen system. New plaster may need the primer or mist-coat stage specified by the product information.
- Protect adjacent surfaces and plan the work so one mixed batch covers a whole wall where possible.
- Apply the manufacturer’s recommended film thickness and recoat only after the preceding coat is ready; do not stretch paint to make a tin last.
Read the exact tin and technical sheet for drying and recoat instructions because those timings differ by product and are not interchangeable between retail and trade lines.
What common mistakes cause a Dulux paint estimate to fail?
- Dividing before multiplying by coats: this underestimates a two-coat job by half. Put the coat count in the numerator.
- Using the best rate for every surface: “up to” 14 or 18 m²/litre assumes conditions that a rough or absorbent wall may not meet.
- Treating a one-coat label as a universal promise: Simply Refresh’s one-coat presentation depends on a suitable surface and adequate colour coverage.
- Combining rates from different products: a trade matt figure cannot be used to size a retail matt purchase.
- Ignoring primer: a primer coat is an additional stage when the system calls for it, not a free substitute for topcoat volume.
- Buying the exact decimal: 4.29L is a calculation, not a tin size or a job-site guarantee; round up.
- Failing to allow for a colour change: a significant change may need a third coat even when two coats are normal.
What is the safest way to make a final purchase decision?
Start with the exact product name and finish, not just the word “Dulux”. Copy the coverage figure and coat guidance from the current tin or product page, measure the total area, and run the formula. Then add any primer or extra coat required by the substrate or colour change, round up to the next listed pack and retain the batch information for future touch-ups.
If two products appear suitable, compare their rates only after accounting for coats and preparation. A higher m²-per-litre number does not automatically mean fewer litres if that product requires a primer or if the surface needs an additional coat. The useful comparison is total system volume for the finished result, not the headline rate alone.
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Frequently Asked Questions
Can I use Dulux’s coverage rate for ceilings as well as walls?
Dulux Matt is listed for interior walls and ceilings, but the same rate can still be affected by ceiling texture, porosity and application method. Measure the ceiling separately and confirm that the exact product and finish on your tin include that surface.
Should I buy leftover paint for future touch-ups?
A small reserve can help with later repairs, particularly when colour matching matters. Seal the tin tightly, label the room and date, and store it in the conditions stated on the label; old paint can thicken or change sheen, so it may not reproduce a fresh finish perfectly.
Does a darker colour always need three coats?
No. Coat count depends on the colour transition, substrate, primer and product system. Dulux Trade notes that significant colour changes may require additional coats, but the tin’s coverage and hiding guidance should determine the estimate for your specific colour.
Is a higher m²-per-litre figure always the cheapest option?
Not necessarily. Compare the litres for all required coats, primer and any extra coat for colour change, then compare the available pack sizes. A product with a lower headline price per litre can require more total material if its system needs additional preparation or coats.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
