How much paint do
you actually need?

Free Paint Calculator – How Much Paint Do You Really Need?

Before you buy a single tin of paint, use a reliable paint calculator to know exactly how much you need. The free online paint calculator above removes all guesswork from your next decorating project whether you are refreshing a single bedroom or repainting an entire home. Enter your room dimensions, choose your finish and number of coats, and get a precise litre or gallon figure in seconds.

Buying too little paint means a mid-project trip back to the store and the risk of a colour mismatch between batches. Buying too much means wasted money on paint that sits in a garage for years. A paint coverage calculator like this one ensures you buy exactly what you need, nothing more and nothing less.

How Does a Paint Calculator Work?

A paint coverage calculator works by combining four key variables: the paintable surface area of your room, the coverage rate of your chosen paint, the number of coats you plan to apply, and a waste allowance for spills and touch-ups. Here is the exact step-by-step process our online paint calculator uses:

Step 1: Measure your room

Start by measuring your room’s width, length, and ceiling height. Our paint calculator supports both metric (metres) and imperial (feet) measurements, making it equally useful whether you are in the US, UK, or Europe. For a typical room of 4m × 5m with 2.5m ceilings, the gross wall area is (4+5) × 2 × 2.5 = 45 m². In imperial, a 13ft × 16ft room with 8ft ceilings gives (13+16) × 2 × 8 = 464 sq ft.

Step 2: Subtract doors and windows

Doors and windows are not painted with wall paint, so any accurate paint coverage estimator subtracts them from the total area. A standard interior door covers approximately 1.9 m² (20 sq ft) and a standard window covers approximately 1.4 m² (15 sq ft). Our paint calculator handles this automatically just enter the number of doors and windows in your room.

Step 3: Add the ceiling if needed

If you are painting the ceiling as well as the walls, toggle the ceiling option in our online paint calculator. Ceiling paint is typically different from wall paint usually a flat or matt finish so you may want to calculate walls and ceiling separately for the most accurate paint coverage calculator result.

Step 4: Choose your paint finish

Different paint finishes have different coverage rates, which directly affects how much paint you need. Our paint coverage estimator adjusts automatically based on your chosen finish:

• Matt / Flat: 12 m²/L (400 sq ft/gal) – highest coverage, best for ceilings and bedrooms
• Eggshell: 11 m²/L (380 sq ft/gal) – subtle sheen, great for living rooms
• Satin: 10 m²/L (350 sq ft/gal) – the most popular all-round finish
• Semi-gloss: 9 m²/L (320 sq ft/gal) – washable, good for kitchens and bathrooms
• Gloss: 8 m²/L (280 sq ft/gal) – most durable, lowest coverage rate

Step 5: Set your number of coats

Most interior walls need two coats for full, even coverage. If you are painting over a dramatically different colour dark red to white, for example three coats may be necessary. Our painting cost calculator multiplies the base paint requirement by the number of coats you select, giving you a realistic total before waste is added.

Step 6: Add a waste allowance

Every professional decorator adds a buffer for waste. Our paint coverage calculator lets you choose from 5% (smooth, freshly plastered walls), 10% (standard condition), 15% (textured surfaces), or 20% (rough or porous surfaces like bare brick). This final step is what separates a professional estimate from a back-of-the-envelope guess.

Interior Painting Cost Calculator – How Much Does It Cost to Paint a Room?

Paint cost is one of the biggest variables in any decorating budget. Our interior painting cost calculator gives you an instant cost estimate once you enter the price per litre (or per gallon in the US). The painting cost calculator supports USD, GBP, and EUR, so whether you are shopping at a hardware store in New York, London, or Paris, you get a relevant cost estimate in your local currency.

Average paint prices by market

To help you use the painting price calculator accurately, here are typical paint prices across different markets:

• USA: Budget interior paint costs $15–$25 per gallon. Mid-range brands like Behr and Valspar cost $30–$50/gal. Premium brands like Farrow & Ball or Benjamin Moore run $70–$100/gal.
• UK: Budget paint costs £8–£15 per litre. Mid-range brands like Dulux and Crown cost £15–£25/L. Premium brands like Farrow & Ball and Little Greene cost £25–£55/L.
• Europe: Budget paint costs €6–€12 per litre. Mid-range brands cost €12–€22/L. Premium and eco brands typically cost €20–€45/L.

Enter your chosen paint’s price per unit into our painting cost calculator and the tool instantly shows your total estimated paint spend for the entire project.

Full painting project cost – beyond the paint itself

Our interior painting cost calculator covers the paint cost specifically. For a complete project budget, also factor in:

• Primer: New plaster or bare walls need a coat of primer or mist coat before painting. Budget an additional 30% of your paint quantity for primer.
• Tools and supplies: Rollers, brushes, painter’s tape, drop cloths, and trays add $30–$80 / £25–£60 / €25–€70 to a typical project.
• Labour: If hiring a professional painter, expect to pay $2–$6 per sq ft in the US, £8–£15 per m² in the UK, and €7–€14 per m² in Europe on top of materials.

Paint Coverage Calculator – Understanding Coverage Rates

Coverage rate is the single most important number in any paint coverage calculator. It tells you how many square metres (or square feet) one litre (or gallon) of paint will cover in a single coat. Coverage rates are always printed on the paint tin, but here is what to expect from different paint types:

Metric coverage rates (m² per litre)

• Masonry paint: 4–6 m²/L (highly porous surface absorbs more paint)
• Undercoat / primer: 8–10 m²/L
• Matt emulsion: 10–12 m²/L
• Vinyl silk / satin: 9–11 m²/L
• Gloss: 7–9 m²/L
• Ceiling paint: 10–13 m²/L

Imperial coverage rates (sq ft per gallon)

• Masonry paint: 150–200 sq ft/gal
• Primer / undercoat: 280–350 sq ft/gal
• Flat / matt paint: 350–400 sq ft/gal
• Eggshell: 350–380 sq ft/gal
• Satin: 300–350 sq ft/gal
• Semi-gloss: 280–320 sq ft/gal
• Gloss: 250–300 sq ft/gal

Always use the coverage rate printed on your specific paint tin for the most accurate paint coverage estimator result. The figures above are averages premium paints with higher pigment loads often achieve the upper end of these ranges, while budget paints may fall at the lower end.

Painting Cost Calculator – Room by Room Guide

Different rooms have different painting requirements. Here is a room-by-room guide to help you use our painting cost calculator and painting price calculator most effectively:

Bedroom paint calculator

A standard UK double bedroom (3.5m × 3.5m, 2.4m ceiling) has approximately 33 m² of wall area. After subtracting a door and two windows, the net area is around 28 m². At 2 coats of satin (10 m²/L) plus 10% waste, you need approximately 6.2 litres of paint. At £15/L mid-range, that is around £93. Use our interior painting cost calculator above to get an exact figure for your specific room.

Living room paint calculator

A typical living room (4.5m × 5.5m, 2.5m ceiling) has approximately 50 m² of gross wall area. After subtracting a door and three windows, the net area is around 43 m². At 2 coats of eggshell (11 m²/L) plus 10% waste, expect approximately 8.6 litres. Our painting price calculator will calculate the cost at your local paint price.

Kitchen paint calculator

Kitchens need a washable finish satin or semi-gloss. A standard kitchen (3m × 4m, 2.4m ceiling) has around 33 m² gross area. With a door, two windows, and often a significant portion of wall behind units that doesn’t need painting, net paintable area may be as low as 22–26 m². Our paint calculator gives you a precise figure once you enter your actual dimensions.

Bathroom paint calculator

Bathrooms need moisture-resistant paint typically semi-gloss or gloss. At a smaller footprint (usually 2m × 2.5m, 2.4m ceiling), gross wall area is around 22 m². A door and window bring net area down to approximately 19 m². At 2 coats of semi-gloss (9 m²/L) plus 10% waste, expect 4.7 litres.

Whole house paint calculator

For whole-house projects, run our online paint calculator for each room individually and sum the results. This gives you a room-by-room breakdown and a precise total, rather than a rough estimate. Many professional decorators use exactly this approach room by room when preparing quotes for clients.

Painting Price Calculator How to Save Money on Your Paint Project

Once your painting price calculator gives you a total paint cost, here are proven ways to reduce it without compromising on quality:

• Buy in bulk. Larger tins (5L vs 2.5L, or gallon vs quart) almost always have a lower cost per litre or gallon. Our paint calculator recommends the optimal tin size for your project.
• Use a mid-sheen for most surfaces. Satin covers well and is cleanable you do not always need the most expensive matt or the premium gloss. Reserve specialist finishes for where they matter most.
• Prepare surfaces properly. Filling cracks, sanding, and priming bare patches before painting means your topcoat goes further and requires fewer coats directly reducing the result of your painting cost calculator.
• Don’t overbuy. Use our paint coverage calculator to buy exactly the right amount. Leftover paint is wasted money and difficult to dispose of responsibly.
• Compare coverage rates. A £20/L paint that covers 12 m²/L may be more economical than a £12/L paint that only covers 8 m²/L. Our painting price calculator makes this comparison easy.

Paint Coverage Estimator – Common Mistakes to Avoid

Even with a paint coverage estimator, people make avoidable mistakes. Here are the most common ones and how to avoid them:

• Ignoring surface porosity. Raw plaster, bare wood, and masonry absorb far more paint than finished walls. Always add a primer coat and increase your waste allowance to 20% on porous surfaces.
• Forgetting the ceiling. Ceilings are often the largest single surface in a room. Always include them in your paint coverage calculator estimate, even if you use a separate ceiling paint.
• Using coverage rates from the wrong finish. The coverage rate printed on a matt tin does not apply to gloss. Always match the coverage rate in your paint coverage estimator to the exact finish you are using.
• Not accounting for dark-to-light colour changes. Going from a deep colour to a lighter one requires more coats sometimes three or four to fully cover the old colour. Our paint calculator lets you adjust the number of coats to reflect this.
• Buying from different batches. If your painting price calculator result means you need to buy across multiple shops or trips, always check that the batch number on the tin matches. Batch differences are nearly invisible when wet but show clearly once dry.

Online Paint Calculator – Why Ours is Built for Home Decorators

There are many online paint calculator tools available, but most are built for professional contractors or are locked to a specific paint brand. Decorateva’s free paint calculator is designed specifically for home decorators and DIY enthusiasts across the US, UK, and Europe. Here is what makes it different:

• Both metric and imperial. Switch between metres and feet with a single click the only online paint calculator you need whether you are in Boston, Birmingham, or Berlin.
• Multi-currency cost estimates. Get your project cost in USD, GBP, or EUR, making it a true international interior painting cost calculator.
• Full breakdown, not just a total. See every step of the calculation gross area, deductions, net area, coverage, coats, and waste, so you understand exactly where your number comes from.
• Smart tin suggestions. Instead of just giving you a litre total, our paint coverage calculator tells you exactly how many 2.5L and 5L tins (or quarts and gallons) to buy.
• No sign-up, no ads, completely free. Use our painting cost calculator as many times as you like, for as many rooms as you like, with no limits.

Whether you are planning a single room refresh or a full home repaint, our free paint calculator is the fastest, most accurate way to know exactly how much paint to buy and exactly how much it will cost. Use the online paint calculator above, get your results in seconds, and walk into the paint store with confidence.

Looking for more inspiration? Browse our latest living room ideas and explore all our free interior design tools on Decorateva.