Free Paint Calculator UK – How Much Paint Do I Need?
Planning to decorate a room and wondering how much paint you need?
Our free Paint Calculator UK helps you estimate the number of litres of paint required for your walls before you start decorating.
Whether you’re painting a bedroom, living room, kitchen, hallway or home office, buying the right quantity of paint can help reduce unnecessary expense and avoid running out halfway through the job.
Simply enter your room dimensions, select the number of coats and enter your paint’s coverage rate.
The calculator will estimate:
- Total wall area in square metres.
- Area to subtract for doors and windows.
- Net paintable wall area.
- Paint required for one or more coats.
- Extra paint for waste and touch-ups.
- Suggested paint tin quantities.
Results are estimates. Always check the coverage and application instructions supplied by your paint manufacturer.
Paint Calculator
Find out how many litres of paint you need for your room.
Your Paint Estimate
Includes your selected extra allowance.
Suggested Paint Tin Combination
Based on common 1 L, 2.5 L, 5 L and 10 L tin sizes. This suggestion minimises the volume purchased, then the number of tins. Check available sizes and prices with your retailer.How Your Result Was Calculated
Results are estimates. Paint coverage depends on the surface, paint type, preparation and application. A primer or mist coat may need separate calculation.
Helpful Products
How Much Paint Do I Need for a Room?
The amount of paint needed depends on the size of the room, the number of coats and the coverage rate of the paint.
For a typical rectangular room, the calculation begins by measuring the length, width and height.
You then calculate the total wall area, subtract doors and windows, and allow for the number of coats.
Example: Painting a 4 m × 3 m Bedroom
Suppose your bedroom measures:
- Length: 4 metres.
- Width: 3 metres.
- Wall height: 2.4 metres.
- Doors: 1.
- Windows: 1.
- Coats required: 2.
- Paint coverage: 12 m² per litre.
- Extra allowance: 10%.
The total wall area is 33.6 m².
After subtracting an estimated 1.8 m² for the door and 1.5 m² for the window, the paintable area is 30.3 m².
Two coats require coverage of 60.6 m².
At 12 m² per litre, this requires 5.05 litres before the extra allowance.
Adding 10% gives an estimated 5.56 litres of paint.
For this example, buying one 5-litre tin and one 1-litre tin would provide 6 litres.
How to Use Our Free Paint Calculator
Step 1: Measure Your Room
Measure the room’s length, width and wall height in metres.
If your room has an unusual shape, you can calculate the wall area separately and enter the total directly.
Step 2: Subtract Doors and Windows
Enter the number of doors and windows.
Our calculator uses approximate areas of 1.8 m² per door and 1.5 m² per window.
For greater accuracy, measure your actual openings and adjust the deductions.
Step 3: Choose the Number of Coats
Most decorating projects require more than one coat, but the correct number depends on the paint, surface condition and colour change.
Follow the manufacturer’s guidance.
Step 4: Enter Paint Coverage
Paint coverage is normally displayed on the tin in square metres per litre (m²/L).
Enter the stated coverage figure.
Step 5: Add a Waste Allowance
You can include an additional percentage to account for variations in application, small losses and touch-ups.
Step 6: Calculate Your Paint
Click Calculate Paint Required to view your estimate in litres and a suggested combination of paint tins.
Paint Calculator Formula Explained
Our calculator uses the following method.
Calculate the Wall Area
For a rectangular room:
Wall Area = 2 × (Length + Width) × Height
Subtract Doors and Windows
Paintable Area = Wall Area − Openings
Calculate Paint Quantity
Paint Required = (Paintable Area × Number of Coats) ÷ Coverage per Litre
Finally, multiply the result by your selected waste allowance.
For example, a 10% allowance means multiplying the calculated quantity by 1.10.
Paint Coverage Chart – How Much Area Does a Litre Cover?
Different paints have different coverage rates.
The following table illustrates how much wall area various paint quantities could cover, assuming 12 m² per litre and one coat.
| Paint Quantity | Approximate Coverage |
|---|---|
| 1 litre | 12 m² |
| 2.5 litres | 30 m² |
| 5 litres | 60 m² |
| 7.5 litres | 90 m² |
| 10 litres | 120 m² |
| 15 litres | 180 m² |
For two coats, the area that can be fully painted is approximately half the one-coat area.
These are mathematical examples rather than guaranteed paint coverage figures. Actual coverage depends on the product and surface.
How Much Paint Do I Need for Two Coats?
If your walls need two coats, you will generally need approximately twice the quantity required for one coat, assuming the same coverage rate.
For example, if one coat requires 2.5 litres, two coats would require approximately 5 litres before any additional allowance.
Some paints may require a primer, undercoat or different application method.
Check the manufacturer’s instructions before purchasing.
How Much Paint Do I Need for a Bedroom?
Bedroom paint requirements vary with room size, wall height, doors, windows and the number of coats.
Here are some illustrative estimates using a wall height of 2.4 metres, one standard door, one standard window, two coats, 12 m² per litre coverage and a 10% allowance.
| Room Dimensions | Approximate Paint Required |
|---|---|
| 3 m × 3 m | 4.68 litres |
| 4 m × 3 m | 5.56 litres |
| 4 m × 4 m | 6.44 litres |
| 5 m × 4 m | 7.32 litres |
| 5 m × 5 m | 8.20 litres |
Use our Paint Calculator for a more relevant estimate based on your own measurements.
Should You Deduct Doors and Windows?
Yes, subtracting the area of doors and windows can improve the accuracy of a paint estimate.
However, small openings may not make a significant difference, especially when you also allow for waste.
For accurate measurements, calculate the height multiplied by the width of each opening.
If you are also painting doors, frames or window surrounds, calculate those surfaces separately using the appropriate paint coverage.
es.
How Much Extra Paint Should You Buy?
An extra allowance can be useful because real-world paint consumption does not always match the coverage printed on the tin.
Reasons include:
- Porous plaster or other absorbent surfaces.
- Textured walls.
- Uneven application.
- Paint left in trays or rollers.
- Small touch-ups.
- Variations in coverage between coats.
Our calculator lets you choose an allowance between 0% and 20%.
The appropriate amount depends on the project and the manufacturer’s guidance.
Do You Need More Paint for New Plaster?
New plaster may absorb paint differently from an existing painted wall.
It may require an appropriate primer or mist coat before the finishing coats.
Follow the paint manufacturer’s instructions for newly plastered surfaces, including any recommended drying and preparation requirements.
The Paint Calculator estimates finishing paint quantities. Primer or mist coat quantities should be calculated separately using the relevant product’s coverage.
How Much Paint Do You Need for a Ceiling?
For a rectangular ceiling, multiply the room’s length by its width.
For example:
4 m × 3 m = 12 m²
If the ceiling paint covers 12 m² per litre, one coat would require approximately 1 litre before any extra allowance.
Two coats would require approximately 2 litres.
Ceilings should generally be calculated separately from walls because they may use a different paint.
Is It Better to Buy One Large Paint Tin or Several Small Tins?
Larger paint tins can sometimes offer a lower price per litre, but this is not always the case.
Before buying, compare:
- Price per litre.
- Available tin sizes.
- Amount of paint required.
- Whether you expect to need paint for future touch-ups.
- Storage and shelf-life guidance.
Our calculator suggests tin combinations based on the amount required, rather than comparing retailer pric
Frequently Asked Questions
How much paint do I need for a 4 m × 3 m room?
For a room with 2.4 m high walls, one standard door and window, two coats and paint covering 12 m² per litre, our calculator estimates approximately 5.56 litres including a 10% allowance.
How much does 5 litres of paint cover?
At an illustrative coverage rate of 12 m² per litre, 5 litres covers approximately 60 m² for one coat or 30 m² for two coats.
Is 2.5 litres enough to paint a bedroom?
It depends on the size of the bedroom, the number of coats and the paint’s coverage. A small feature wall may require less than 2.5 litres, while a complete bedroom could require considerably more.
How do I calculate wall area in square metres?
Multiply each wall’s length by its height, then add the areas together. For a rectangular room, use 2 × (length + width) × height.
Does the Paint Calculator include doors and windows?
Yes. You can enter the number of standard-sized doors and windows and add further deductions.
Does the calculator include two coats?
Yes. You can select one, two, three or four coats.
Does the calculator work for ceilings?
You can use the known-area option to estimate ceiling paint separately. Enter the ceiling area and select the appropriate coverage and number of coats.
Can I use this calculator for exterior walls?
The basic area calculation can be used for exterior surfaces, but exterior paints, masonry textures and surface conditions may require different coverage rates and allowances.
Is the Paint Calculator free?
Yes. Calculator Central’s Paint Calculator is free to use without registration.
Recommended Painting and Decorating Equipment
Once you’ve calculated how much paint you need, you may also need the right decorating equipment.
Useful products include:
- Paint rollers and roller trays.
- Quality paintbrushes.
- Masking and painter’s tape.
- Dust sheets and floor protection.
- Filling knives and wall fillers.
- Sandpaper and sanding blocks.
- Measuring tapes or laser distance measurers.
Choose equipment suitable for your paint type and the surfaces you are decorating.
Some recommended product links may be affiliate links. We may earn a commission from qualifying purchases at no additional cost to you.
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Tile Calculator: Estimate tiles for floors and walls.
Appliance Running Cost Calculator: Estimate electricity costs using appliance wattage and your energy tariff.
Calculate Your Paint Requirements Today
Avoid unnecessary guesswork when planning your next decorating project.
Our free Paint Calculator UK helps you estimate paint quantities based on room dimensions, doors, windows, number of coats and paint coverage.
Enter your measurements above to find out approximately how many litres of paint you need.
Calculate it simply with Calculator Central.
Disclaimer: Results are estimates for planning purposes. Always check actual dimensions, surface condition, paint coverage and manufacturer recommendations before purchasing.