How Much Paint and Putty for a Room or Flat – Room-by-Room Calculation
Short answer: for a 4 × 5 m room with a height of 2.6 m, a 2 m² door and 3 m² of windows, the net area of walls and ceiling is 61.8 m², so you need about 93 kg of putty (4 bags of 25 kg) and 16 L of paint for two coats (2 buckets of 15 L). A flat with three rooms, a hallway and a bathroom has 168.74 m²: 254 kg of putty (11 bags) and 43 L of paint (3 buckets).
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When you need this calculation
You need this calculation when you want to know, before you buy, how many bags of putty and buckets of paint a room or a whole flat takes. The most common mistake is the area: the ceiling or the hallway is forgotten, or doors and windows are not subtracted, which means a second trip to the shop or leftover paint in the basement.
For each room the calculator works out the wall and ceiling area, subtracts the openings, adds up all rooms and converts the area into kilograms of putty and litres of paint, rounded up to whole 25 kg bags and 15 L buckets. With the Drywall (Plasterboard) option it also calculates boards, profiles, screws and joint filler.
Who the calculator is for
- Homeowners who skim and paint themselves and want to know how much material to buy.
- Painters, decorators and contractors who need a quick quantity for a quote.
- Anyone moving on to skimming and painting after plastering who wants to carry the areas over without typing them in again.
- Planning the cost of the finishing work.
How to use the paint and putty calculator – step by step
- 1. Under Options turn on what you need: Putty, Paint (2 coats) and, if required, Drywall (Plasterboard).
- 2. Choose the input mode: Rooms if you enter dimensions, or Total area if you already know the wall and ceiling area.
- 3. For each room enter the length, width and height. The default height is 2.6 m. Add more rooms with the Add button.
- 4. Enter the total area of windows and doors in m² – it is subtracted from the wall area.
- 5. Use the Walls and Ceilings switches to choose what is being finished in that room.
- 6. If you turned on Drywall, choose the board size (1.2 × 2 m or 1.25 × 2 m) and the finish level Q1, Q2 or Q3.
- 7. Click Calculate, then save the result to a project or export a PDF.
A flat room by room: what to enter for each room
Enter each room separately and rename it. Change the height only where it differs from the default 2.6 m. Windows and doors are entered as a total area in m²; count 2 m² for one interior door.
A door between two rooms is subtracted in both, because both sides of the wall are finished, so a hallway with four doors has 8 m² of openings. Enter a bathroom tiled up to the ceiling with the Walls switch turned off. The result shows walls and ceilings separately, and putty and paint for the total area.
Calculation examples
Living room 4 × 5 m, height 2.6 m, door 2 m², windows 3 m², with ceiling: walls 18 × 2.6 − 5 = 41.8 m², ceiling 20 m², total 61.8 m². Putty 61.8 × 1.5 = 92.7, so 93 kg or 4 bags (100 kg). Paint 61.8 × 0.25 = 15.45, so 16 L or 2 buckets (30 L).
Bedroom 3.5 × 3 m, height 2.6 m, door 2 m², window 1.5 m², with ceiling: walls 13 × 2.6 − 3.5 = 30.3 m², ceiling 10.5 m², total 40.8 m². Putty 62 kg, so 3 bags (75 kg). Paint 10.2, so 11 L or 1 bucket of 15 L.
Example flat and a ceiling in a different colour
Flat with a height of 2.6 m, all rooms with ceiling, 168.74 m² in total. The putty is the same whatever the colour. If the ceiling is white and the walls are coloured, in Total area mode enter 119.9 m² with only the Walls switch on: 30 L (2 buckets), and then 48.9 m² with only Ceilings on: 13 L (1 bucket). One living room wall of 5 × 2.6 m (13 m²) in a different colour needs 4 L, and the other walls (106.9 m²) 27 L.
| Room | Dimensions, openings | Walls | Ceiling |
|---|---|---|---|
| Living room | 4 × 5 m, 5 m² | 41.8 m² | 20 m² |
| Bedroom | 3.5 × 3 m, 3.5 m² | 30.3 m² | 10.5 m² |
| Children's room | 3.2 × 3 m, 3.5 m² | 28.74 m² | 9.6 m² |
| Hallway | 4 × 1.2 m, 8 m² | 19.04 m² | 4.8 m² |
| Bathroom | 2.2 × 1.8 m, tiles | – | 3.96 m² |
| Total | 119.9 m² | 48.9 m² |
Primer and plasterboard
The calculator does not list primer as a separate item. It is applied to the same net area the calculator shows, so simply multiply that area by the primer consumption from the manufacturer's instructions.
With the Drywall (Plasterboard) option the calculator works out, for the same total area, the boards, 4 m CD 60/27 profiles (2 m per m²), drywall screws (25 pieces per m², in boxes of 500) and joint filler in 25 kg bags: Q1 – Basic 0.25 kg/m², Q2 – Standard 0.4 kg/m², Q3 – Fine 0.6 kg/m². For a 20 m² suspended ceiling that is 9 boards of 1.2 × 2 m, 10 profiles, 500 screws and 8 kg of filler for Q2. For consumption per m² and a quick table by area, see the guide “How Much Putty per m²: Skim Coat Consumption for Walls and Ceilings”.
The most common mistakes when calculating paint and putty
- Forgetting the ceiling or not subtracting windows and doors.
- A door between two rooms subtracted in only one of them.
- Assuming a single coat – the calculator works with two coats of putty and two coats of paint.
- Dark colours and paints with poor coverage often need a third coat, so add paint accordingly.
- Absorbent or uneven walls use more material.
- Painting fresh putty without primer, so the putty soaks up part of the paint.
- The 1.5 kg/m² value applies to thin finishing coats of putty, not to levelling out larger unevenness.
What else to calculate along with putty and paint
Walls often need plastering before skimming: the Plastering calculator works out the plaster, and its Areas to the paint calculator button carries wall areas including reveals and ceiling areas straight into this calculator. For partition walls and suspended ceilings use the Drywall calculator, and for external walls the Facade (ETICS) calculator. For irregular rooms use the Surface Areas calculator. You can save all calculations to the same project and export them as a single PDF.
Frequently asked questions
How much paint do I need for a 4 × 5 m room?
With a height of 2.6 m, 5 m² of openings and the ceiling, the net area is 61.8 m², so two coats need 16 L of paint (2 buckets of 15 L).
How do I calculate paint for a whole flat with several rooms?
Enter each room with its openings, and a tiled bathroom with the ceiling only. For the example flat (168.74 m²) that is 254 kg of putty (11 bags) and 43 L of paint (3 buckets).
Does primer need to be calculated separately?
Yes. The calculator does not work it out separately, so multiply the net area from the result by the primer consumption from the manufacturer's instructions.
How do I calculate paint if the ceiling and walls are different colours?
The putty stays based on the total area, while the paint is calculated in Total area mode separately for the walls and for the ceiling: 30 L for 119.9 m² of walls, 13 L for 48.9 m² of ceiling.
Is the putty and paint calculation free?
Yes. The calculator is free on the web and in the Android app, where calculations are saved to projects and exported to PDF.
Calculate yours: Paint, Putty & Plasterboard
Guides: Paint Consumption per m²: How Much Paint for Walls and Ceiling · How Much Putty per m²: Skim Coat Consumption for Walls and Ceilings