Paint Calculator Guide UK 2025

Planning a decorating project in the UK? Whether you're refreshing a single room or redecorating your entire home, calculating the right amount of paint saves money and multiple trips to the shop. This comprehensive guide explains how to calculate paint quantities accurately for walls, ceilings, woodwork, and exteriors.

Getting your paint quantities right is more than just convenience—running out mid-project can mean colour matching issues, while buying too much wastes money on paint that may dry out before you use it.

Understanding Paint Coverage Rates

Paint coverage varies significantly depending on the type of paint, surface condition, and application method. Here are typical coverage rates for common paint types in the UK:

How to Measure Your Room

Accurate measurements are essential for calculating paint quantities. Here's how to measure different surfaces:

Walls

1. Measure the height from floor to ceiling (typically 2.4m in UK homes)
2. Measure the width of each wall
3. Multiply height × width for each wall
4. Add all wall areas together
5. Subtract window and door areas (standard door = 2m², window = 1.5m²)

Ceilings

1. Measure room length × room width
2. This gives you the ceiling area in square metres

Standard UK Room Paint Requirements

Here are pre-calculated estimates for typical UK room sizes:

Factors That Affect Paint Coverage

Several factors can increase or decrease how much paint you actually need:

• Surface texture: Rough or textured surfaces absorb more paint (reduce coverage by 20-30%)
• Surface porosity: New plaster requires a mist coat first; bare wood needs primer
• Colour change: Dark to light or vice versa may need 3+ coats
• Paint quality: Premium paints often have better coverage
• Application method: Rollers use slightly more paint than brushes
• Ambient temperature: Very cold or hot conditions affect absorption

How Many Coats Do You Need?

2025 UK Paint Prices

Budget for your project with these typical UK paint prices:

Popular UK Paint Brands

Trusted paint brands available in the UK include:

• Dulux: UK's most popular brand, wide colour range
• Crown: Good quality, competitive pricing
• Farrow & Ball: Premium heritage colours
• Little Greene: Eco-friendly, period colours
• Johnstone's: Trade quality, excellent durability
• Leyland: Budget-friendly DIY option

Paint Coverage Calculations Explained

Accurate paint coverage calculation prevents the common frustrations of running out mid-project or wasting money on excess paint. The fundamental calculation involves determining the total paintable surface area, subtracting non-paintable areas such as windows and doors, and then dividing by the paint's coverage rate per litre. Most standard UK emulsion paints cover between 12 and 14 square metres per litre per coat, though this varies depending on the paint quality, surface porosity, and application method.

For a typical UK room measuring 4 metres by 3 metres with a ceiling height of 2.4 metres, the wall area calculation works as follows. The room perimeter is 14 metres (4 + 3 + 4 + 3). Multiply by the ceiling height of 2.4 metres to get a total wall area of 33.6 square metres. Subtract the area of a standard door (approximately 1.8 square metres) and a standard window (approximately 1.2 square metres), giving a paintable wall area of 30.6 square metres. At 13 square metres per litre, you would need approximately 2.4 litres per coat, or 4.7 litres for two coats. Rounding up to a 5-litre tin provides a small margin for touch-ups.

Surface preparation significantly affects coverage rates. Freshly plastered walls are highly absite and may require a dedicated mist coat, which is emulsion diluted with water at a ratio of roughly 70 percent paint to 30 percent water. This mist coat seals the plaster and prevents subsequent coats from being absorbed too quickly. Without a mist coat, your topcoats will not spread as far and may appear patchy. Previously painted walls in good condition typically achieve the manufacturer's stated coverage, while textured surfaces such as woodchip or Artex may require up to 50 percent more paint than smooth walls.

UK-Specific Painting Considerations

The UK climate creates specific challenges for interior and exterior painting projects. High humidity levels, particularly in bathrooms and kitchens, require specialist moisture-resistant paints that prevent mould growth and withstand steam exposure. Most major UK paint brands offer bathroom and kitchen-specific formulations with anti-mould additives. For exterior painting, the British weather limits the practical painting season to approximately April through October, with ideal conditions being dry days above 10 degrees Celsius with low humidity.

UK building regulations and conservation requirements can also affect paint choices. Properties in conservation areas may have restrictions on exterior colour changes, requiring planning permission for alterations to the building's appearance. Listed buildings have even stricter requirements, often mandating the use of specific traditional paint types such as limewash for historic masonry rather than modern masonry paint. If your property is listed or in a conservation area, check with your local planning authority before beginning any exterior painting work.

Environmental considerations are becoming increasingly important for UK consumers choosing paint. Low-VOC (Volatile Organic Compound) and zero-VOC paints produce fewer harmful fumes during application and drying, making them preferable for bedrooms, nurseries, and homes with occupants who have respiratory conditions. Several UK brands, including Little Greene, Earthborn, and Lakeland Paints, specialise in environmentally friendly formulations. Water-based paints now dominate the UK market, with oil-based gloss and eggshell paints declining in popularity due to their higher VOC content and longer drying times.

Frequently Asked Questions

How many coats of paint do I need?

For most interior wall painting, two coats of emulsion over a previously painted surface in a similar colour will provide full, even coverage. If you are making a dramatic colour change, such as going from dark to light or vice versa, you may need three coats or a dedicated primer-undercoat first. New plaster requires a mist coat followed by two full coats. Ceilings generally need two coats of matt emulsion. For woodwork, one coat of undercoat followed by one or two coats of gloss or satin provides a durable finish.

What is the difference between matt, silk, and eggshell paint?

Matt paint has a flat, non-reflective finish that hides surface imperfections well, making it the most popular choice for living room and bedroom walls and ceilings. Silk paint has a slight sheen that is easier to wipe clean, making it suitable for hallways, children's rooms, and areas prone to fingermarks, though it highlights imperfections in the wall surface. Eggshell has a subtle satin finish and is more durable than matt, traditionally used on woodwork and in areas requiring regular cleaning. Bathroom and kitchen paints typically have a soft sheen finish with moisture-resistant and anti-mould properties.

How long should I wait between coats of paint?

Most water-based emulsion paints are touch-dry within one to two hours and can be recoated after four hours in good conditions. However, in the UK's typically cooler and more humid environment, allowing six to eight hours between coats is advisable, or leaving overnight for best results. Oil-based paints require 16 to 24 hours between coats. Painting in cold or damp conditions extends drying times significantly, and applying a second coat before the first is fully dry can cause lifting, bubbling, or uneven coverage. Always check the manufacturer's instructions on the tin for specific recoat times.

Frequently Asked Questions

James Mitchell, ACCA

Chartered Accountant & Former HMRC Advisor

James is a Chartered Certified Accountant (ACCA) specialising in UK personal taxation and financial planning. With over 12 years in practice and a background as a former HMRC compliance officer, he brings authoritative insight to complex tax topics.