Exterior Paint Calculator

How to Calculate Exterior Paint for Your House

Painting the outside of your house is one of the highest-impact home improvements you can make — it protects your walls from weather damage and completely transforms the kerb appeal. For interior rooms, our paint calculator covers wall and ceiling estimates with the same formula. The challenge is working out exactly how much paint to buy. Too little means a return trip to the paint shop mid-project; too much means wasted money sitting in tins in your garage.

Our exterior paint calculator takes the guesswork out of the process. Enter your wall dimensions, choose your surface type, and get an instant estimate for paint volume, primer, can sizes, and total cost.

The Exterior Paint Formula

The formula behind the calculator is straightforward:

Paint Needed (L) = (Net Wall Area x Number of Coats) / Coverage Rate x Waste Factor

Where net wall area equals the gross wall area minus windows and doors:

Net Wall Area = (Wall Height x Wall Length x Number of Walls) - (Windows x 1.5 m²) - (Doors x 1.9 m²)

The coverage rate and waste factor depend on your surface type. Rough and porous surfaces absorb more paint, so the coverage rate drops and you should increase the waste allowance.

Coverage Rates by Surface Type

Different exterior surfaces absorb paint at very different rates. Using the wrong coverage figure is the most common reason DIYers run out of paint halfway through a wall.

These figures assume a mid-range masonry paint or exterior wood paint. Premium paints with higher solid content may stretch 10-15% further per litre.

How Much Paint for Different House Sizes

This table gives ballpark figures for standard 2-coat applications on smooth render, with 15% waste. Your actual requirement will vary based on the number of windows, doors, and the surface texture.

Paint costs are based on mid-range masonry paint at approximately EUR 5-7/L. Premium paints can cost EUR 8-12/L.

Step-by-Step: Measuring Your House for Paint

Getting accurate measurements is the key to an accurate paint estimate.

1. Measure wall height — Measure from the base of the wall to the soffit (underside of the roof overhang). For most two-storey houses this is 5-6 metres. Include any gable ends as a separate calculation using the triangular area formula (base x height / 2).

2. Measure wall length — Measure each wall you plan to paint. For a semi-detached house, you typically paint the front, back, and one side. For a detached house, measure all four sides.

3. Count windows and doors — Each standard window subtracts about 1.5 m² and each door about 1.9 m² from the paintable area. Count carefully — a house with 8 windows and 2 doors has about 15.8 m² of openings.

4. Identify your surface — Is it smooth render, textured render, bare brick, painted brick, or wood cladding? This determines the coverage rate.

5. Choose your coats — 2 coats is standard. Use 3 if covering a dark colour or painting bare masonry for the first time.

Choosing the Right Exterior Paint

Not all exterior paints are the same. The three main categories are:

Masonry paint is designed for rendered walls, brick, and concrete. It is water-based, breathable, and flexible enough to cope with the slight expansion and contraction of masonry in changing temperatures. Look for products with a 15-year guarantee.

Exterior wood paint or stain is formulated for timber cladding, fascias, and window frames. It contains UV filters and fungicide to prevent greying and mould. Available in opaque paint or semi-transparent stain finishes.

Brick paint is a specialist formulation for painting bare brick. It penetrates the porous surface better than standard masonry paint and provides a breathable, waterproof finish. Use it when painting brick for the first time.

Common Exterior Paint Mistakes

Avoid these pitfalls to get a professional finish:

• Skipping the pressure wash — Dirt, algae, and loose material prevent paint adhesion. Always pressure wash and let the wall dry for at least 48 hours before painting.
• Painting in the wrong weather — Paint needs 4-6 hours of dry conditions above 10°C to cure. Rain within 2 hours of application can ruin the finish.
• Ignoring cracks and gaps — Fill hairline cracks with flexible exterior filler before painting. Water enters unfilled cracks and lifts the paint from behind.
• Using interior paint outside — Interior paint lacks UV stabilisers, fungicide, and the flexibility needed for exterior temperature swings. It will crack, peel, and fade within a year.
• Thin coats to save paint — Two proper coats at the correct spread rate last years longer than three thin, stretched coats. Follow the manufacturer's coverage guidance.

While you are working on the exterior, consider the rest of the outside of your home. Our roofing calculator helps estimate tiles and battens if the roof also needs attention, and our fence calculator covers panels, posts, and paint for garden boundaries.

How to Reduce Exterior Paint Waste

The 15% waste factor in our calculator accounts for paint left in trays, on rollers, in crevices, and from uneven application. You can reduce waste by:

• Using a paint grid instead of a tray — less paint pooling at the bottom
• Applying paint with an airless sprayer for large flat areas — more even coverage, less roller stipple
• Buying the right nap length for your surface — 18 mm for textured masonry, 12 mm for smooth render
• Keeping the paint well-stirred throughout the job — settled paint gives inconsistent coverage

If you are painting a large house or multiple surfaces, consider getting professional quotes. A professional painter can often buy trade paint at lower prices and will complete the job faster with less waste.

How Much Does It Cost to Paint a House Exterior?

Exterior house painting is a significant investment, but getting the budget wrong — either overspending on unnecessary preparation or underestimating scaffolding and labour — can turn a straightforward project into a stressful one. This section breaks down every cost involved so you can plan accurately, whether you are painting the house yourself or hiring professionals. The calculator above uses your house dimensions and surface type to estimate both material costs and professional labour, giving you a clear picture of DIY versus contractor pricing.

Cost Breakdown by House Type

The total cost of painting a house exterior depends on its size, the number of walls to paint, surface condition, and whether you need scaffolding. Here are realistic 2026 figures for a full exterior repaint with 2 coats of quality masonry paint.

DIY costs include paint, primer, pressure washer hire, fillers, brushes, rollers, and masking materials. Professional costs include all materials, labour, scaffolding, and preparation.

DIY vs Professional: Detailed Cost Comparison

This table compares the full itemised cost of painting a typical semi-detached house (110 m² wall area, smooth render, 2 coats) as a DIY project versus hiring a professional team.

The DIY route saves EUR 800-2,200 in labour but requires 4-7 days of work, comfort with heights (ladder or scaffold work), and the physical stamina for long days of overhead painting. If scaffolding is already needed for another job (roof repairs, guttering), combining projects saves the setup cost.

Cost Per Square Metre Breakdown

Understanding cost per square metre helps you compare quotes from different painters and benchmark your own budget.

When comparing professional quotes, ask whether scaffolding is included or charged separately. Some painters hire scaffolding through a preferred supplier, while others add a markup.

What Affects the Price

Several factors can push the cost up or down from the averages above.

Surface condition is the biggest variable. A house with sound existing paint that just needs a wash and two fresh coats is the cheapest scenario. A house with flaking paint, cracks, and algae growth needs extensive preparation — scraping, filling, treating, and priming — which can add 30-50% to labour time.

Building height directly impacts scaffolding cost. A single-storey bungalow may only need ladders (EUR 0-50 hire), while a three-storey townhouse requires full scaffold towers (EUR 800-1,500). For two-storey houses, basic scaffold is usually EUR 400-800 for a week.

Surface type matters because rough and porous surfaces take longer to paint and use more material. Painting pebbledash render costs 15-25% more than smooth render due to the extra paint needed to fill the textured surface and the slower roller speed.

Access difficulty increases cost when walls border narrow alleyways, conservatories, fragile garden beds, or sloped ground that complicates scaffold placement.

Number of colours adds to the labour. A single-colour job is simplest. If you want different colours for walls, window surrounds, fascias, and soffits, each colour change requires masking and cleanup time.

How to Save Money on Exterior Painting

You can significantly reduce costs without compromising quality:

• Do the preparation yourself — Even if you hire painters for the application, doing the pressure washing, scraping, and filling yourself can save EUR 300-600 in labour. Painters will often reduce their quote if the surface is ready to paint.
• Paint in the off-season — Painters are busiest May through September. Booking for early spring or late autumn can secure a 10-20% discount, provided the weather cooperates.
• Buy paint in bulk — Trade paint from builders' merchants costs 20-30% less than retail paint from DIY stores. A 10L tin is always cheaper per litre than 2.5L tins.
• Combine with other work — If you already need scaffolding for gutter replacement, roof repairs, or window work, add exterior painting to the same scaffold hire period.
• Use quality paint — This sounds counterintuitive, but premium masonry paint (EUR 7-10/L) with a 15-year guarantee costs more upfront but lasts 2-3 years longer than budget paint (EUR 3-5/L), saving a full repaint cycle.

When to Hire a Professional

Hire a professional exterior painter when the job involves work at height above one storey, extensive surface repairs, lead paint removal (pre-1970s houses), or when you simply want a guaranteed finish in a short timeframe. A professional team of 2-3 painters can complete a semi-detached house in 2-3 days, whereas a solo DIYer may take a full week.

Use our free quote tool below to get competitive estimates from local exterior painters. We recommend getting at least 3 quotes and asking each painter to itemise scaffolding, preparation, materials, and labour separately so you can compare like for like.

Budgeting Checklist

Before starting your exterior painting project, confirm you have budgeted for every item:

• Scaffolding or ladder hire
• Pressure washer hire (or professional wash)
• Exterior filler, caulk, and mastic for cracks
• Masonry primer or stabilising solution
• Masonry paint (2 coats minimum)
• Rollers (long-nap for masonry), brushes, extension poles
• Masking tape, plastic sheeting, dust sheets
• Skip hire or waste disposal for old flaking paint
• Contingency (add 10-15% for unexpected repairs)