# Exterior Paint Calculator

> Free exterior paint calculator. Enter your house dimensions and surface type to find how much masonry, render, or cladding paint you need.

Canonical: https://renoquant.com/exterior-paint-calculator
Prices updated: 2026-03

## At a glance

A typical 3-bedroom semi has 100–130 m² of exterior wall area, needing 25–30 litres of masonry paint for two coats (assuming 10 m²/L coverage and 15% waste) — roughly EUR 200–500 in materials. Quality masonry paint lasts 5–8 years on smooth render, 4–6 on rough render or brick, and 3–5 on wood cladding. Paint at 10–25 °C with low humidity and no rain expected for 24 hours; prime bare render, brick, or wood before topcoats.

## 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](/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.

| Surface Type | Coverage Rate (m²/L) | Typical Waste Allowance | Notes |
|---|---|---|---|
| Smooth Render | 10 m²/L | 10-15% | Best coverage; most efficient surface |
| Rough Render (Pebbledash) | 8 m²/L | 15-20% | Textured surface traps paint in crevices |
| Brick (Unpainted) | 6 m²/L | 15-20% | Very porous; first coat soaks in heavily |
| Brick (Previously Painted) | 8 m²/L | 10-15% | Sealed surface gives better coverage |
| Wood Cladding | 10 m²/L | 10-15% | Smooth wood; use exterior wood paint |
| Rough-sawn Timber | 7 m²/L | 15-20% | Textured grain absorbs more paint |

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.

| House Type | Approx. Wall Area (m²) | Paint Needed (2 coats) | Primer Needed | Estimated Paint Cost (EUR) |
|---|---|---|---|---|
| Mid-Terrace (2 walls) | 50-70 | 12-16 L | 7-10 L | EUR 70-110 |
| End-Terrace (3 walls) | 80-110 | 18-25 L | 10-14 L | EUR 110-170 |
| Semi-Detached (3 walls) | 90-130 | 21-30 L | 12-17 L | EUR 125-200 |
| Detached Bungalow | 80-110 | 18-25 L | 10-14 L | EUR 110-170 |
| Detached House (4 walls) | 120-180 | 28-42 L | 15-23 L | EUR 170-280 |
| Large Detached | 180-260 | 42-60 L | 23-33 L | EUR 260-400 |

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](/roofing-calculator) helps estimate tiles and battens if the roof also needs attention, and our [fence calculator](/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.

## Frequently Asked Questions

### How much exterior paint do I need for a 3-bedroom house?

A typical 3-bedroom semi-detached house has about 100-130 m² of exterior wall area. With 2 coats on smooth render at 10 m²/L and 15% waste, you need roughly 25-30 litres of masonry paint. Use our calculator above for an exact figure based on your house measurements.

### How many coats of exterior paint do I need?

Most exterior surfaces need 2 coats for full coverage and durability. Apply 3 coats when painting over a much darker colour, on bare render, or on very porous brick. One coat is only suitable for maintenance touch-ups on well-maintained surfaces.

### What is the best time of year to paint a house exterior?

Late spring to early autumn is ideal — you need at least 2 consecutive dry days with temperatures above 10°C. Avoid painting in direct hot sun (above 30°C), high humidity (above 85%), frost risk, or windy conditions that carry dust onto wet paint.

### Do I need primer before exterior paint?

Yes, apply primer on bare render, new brickwork, bare wood, or any surface where the old paint has been fully stripped. Primer seals the surface, improves adhesion, and reduces how much topcoat the wall absorbs. Skip primer only when recoating sound existing paintwork.

### How long does exterior house paint last?

Quality masonry paint lasts 5-8 years on smooth render, 4-6 years on rough render or brick, and 3-5 years on wood cladding. Lifespan depends on paint quality, surface preparation, weather exposure, and the number of coats applied.

### Should I use a roller or sprayer for exterior paint?

A long-nap roller (18-22 mm) works well for textured masonry and brick. An airless sprayer is faster for large flat areas like smooth render, but requires masking and overspray protection. Brushes are best for cutting in around windows, doors, and edges.

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Interactive version with calculator: https://renoquant.com/exterior-paint-calculator. Figures are estimates; final quotes vary by site conditions, materials, and region.