Paint Calculator
Stop guessing and avoid costly waste. Calculate exactly how many litres of paint you need for your walls and ceiling based on room dimensions, coats, and coverage rates.
Calculate Your Paint Requirements
Enter your room dimensions and project details below. The calculator will deduct standard openings and factor in your desired number of coats to show the total litres required.
Paint Volume Solver
Project your paint needs based on room size, openings, and coverage rates
Painting Quick Facts
Essential insights for UK DIY and professional decorators
Understanding Paint Estimation
Calculating the exact volume of paint needed prevents mid-project trips to the hardware store and minimises environmental waste. Here is how the math works.
Calculate Gross Wall Area
Add the width and length of the room, multiply by two to get the perimeter, and then multiply by the room height to find the total gross wall area.
Deduct Openings
Subtract the area of doors (approx. 2.0 sq m each) and windows (approx. 1.5 sq m each) to find the true net paintable wall area.
Factor in Coats and Ceilings
Multiply the net wall area (plus any ceiling area) by the number of coats you plan to apply to get the total square metres that need to be covered.
Divide by Coverage Rate
Divide the total coverage area by the paint’s stated coverage rate (sq m per litre) to determine the exact number of litres required.
UK Paint Coverage Benchmarks
Average coverage rates for common types of paint used in UK residential and commercial projects.
| Paint Type | Average Coverage (sq m / Litre) | Best Used For |
|---|---|---|
| Standard Emulsion | 10 – 12 sq m | General interior walls and ceilings (matte or silk finish). |
| Premium Emulsion | 12 – 14 sq m | High-traffic areas, offering better opacity and washability. |
| Wood & Metal Gloss/Satin | 10 – 12 sq m | Skirting boards, doors, radiators, and metalwork. |
| Exterior Masonry Paint | 6 – 8 sq m | External brick, render, or pebbledash (textured surfaces absorb more). |
| Primer / Undercoat | 10 – 12 sq m | Bare wood, metal, or stained surfaces to ensure topcoat adhesion. |
Paint Calculator FAQ
Answers to the most frequently asked questions about paint estimation, coverage, and preparation in the UK.
On average, standard emulsion paint covers 10 to 12 square metres per litre. Premium emulsions can cover 12 to 14 square metres, while exterior masonry paint typically covers 6 to 8 square metres per litre due to surface texture and porosity.
Yes, it is highly recommended for accuracy. A standard internal door deducts approximately 2.0 square metres, and a standard window deducts about 1.5 square metres from your total paintable wall area.
For most colour changes, two coats of paint are required for full, even coverage. If you are painting over new plaster, a diluted ‘mist coat’ is needed first, followed by two topcoats. Drastic colour changes (e.g., dark to light) may require a primer plus two coats.
Yes, it is always advisable to purchase 10% to 15% more paint than the calculator recommends. This accounts for spillage, uneven surfaces, and ensures you have matching paint for future touch-ups, as paint batches can vary slightly in colour over time.