How Much Self-Leveling Compound for a Whole Flat: Layer Thickness and Bags per Room
Short answer: if a 5.2 × 4 m living room and a 5 × 4 m bedroom need a 3 mm layer and a 3 × 2.5 m kitchen needs an 8 mm layer, the flat needs 311 kg of self-leveling compound, which is 13 bags of 25 kg. The rooms are calculated together (209 kg) and the kitchen separately (102 kg), and you add up kilograms, not bags. The Self-Leveling Compound calculator works with one thickness per calculation.
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When you need this calculation
Self-leveling compound is bought in bags, and the floor is poured in one go. If you run out halfway through the room, the new batch bonds to an edge that has already set and you get a visible joint or step. If you buy too much, opened bags quickly go off because of moisture. In a flat, rooms rarely need the same thickness.
The calculator adds up the area of the rooms in one calculation, multiplies it by the consumption for the selected thickness, rounds the kilograms up and converts them into whole 25 kg bags. You can save the result to a project or export it as a PDF materials list.
Who the calculator is for
- Homeowners who level the floor themselves before laying tiles, laminate, parquet or vinyl.
- Tradespeople and floor layers who need a quick quantity for a quote or an order for a whole flat, room by room.
- Anyone comparing layer thicknesses: you immediately see how many more bags 5 mm needs compared with 3 mm.
- Cost planning: with a known price per bag, the number of bags immediately gives a rough cost of the compound.
How to use the self-leveling compound calculator – step by step
- 1. Choose the layer thickness from 1 to 30 mm. The default is 3 mm, and the consumption per m² for that thickness is shown right below the selector.
- 2. Choose the input mode: Rooms or Total area.
- 3. In Rooms mode enter the length and width of each room. You can rename a room (e.g. kitchen, hallway) and add the next one with the Add button. The area of each room is shown below its dimensions.
- 4. If you already know the area, enter it directly in m² in Total area mode.
- 5. Click Calculate. You get the total area, thickness, consumption per m², total kilograms and the number of 25 kg bags.
- 6. When signed in, save the calculation to a project or export a PDF for the shop and the contractor.
A flat with different thicknesses: one calculation per thickness
All rooms in one calculation get the same thickness. So enter the 3 mm rooms in one calculation and the 8 mm kitchen in another, and save both to the same project.
For buying, add up the kilograms from all calculations and only then divide the total by 25. Adding up the bags would give 14, and with a separate calculation for each room as many as 15, because every calculation rounds up. With 311 kg and 13 bags you have 14 kg extra for mixing losses.
| Room | Area | Thickness | Amount | Bags separately |
|---|---|---|---|---|
| Living room | 20.8 m² | 3 mm | 107 kg | 5 |
| Bedroom | 20 m² | 3 mm | 102 kg | 5 |
| Both rooms, one calculation | 40.8 m² | 3 mm | 209 kg | 9 |
| Kitchen | 7.5 m² | 8 mm | 102 kg | 5 |
| Flat, total kilograms | 48.3 m² | – | 311 kg | 13 |
Calculation examples
Room 4.5 × 3.6 m, 4 mm layer: the area is 16.2 m², the consumption 1.7 × 4 = 6.8 kg/m². You need 16.2 × 6.8 = 110.16 kg, rounded up to 111 kg. That is 111 ÷ 25 = 4.44, so 5 bags (125 kg).
Flat with three rooms, 3 mm layer: living room 5.2 × 4 m (20.8 m²), bedroom 3.8 × 3.5 m (13.3 m²) and hallway 4 × 1.2 m (4.8 m²), total 38.9 m². The consumption is 5.1 kg/m², you need 198.39 kg, rounded up to 199 kg, which is 8 bags (200 kg). Only 1 kg is left over, so here it makes sense to buy one extra bag.
Thresholds, doors and pouring order
The thickness changes at the door line, not in the middle of a room. Put a stop bar at the threshold so that the compound from the thicker layer does not run into the next room. The compound layer plus the floor covering with its adhesive should give the same finished floor height on both sides of the threshold; if the kitchen gets tiles and the rooms laminate, include the difference in the compound thickness.
Apply primer and edge strip in all rooms before the first pour, and pour from the room farthest away towards the exit, each room in one go. If you pour everything on the same day, the rest of an opened bag goes into the next room and the total of 13 bags applies; if you pour the kitchen and the rooms several days apart, count 9 + 5 = 14 bags. For consumption per m² and a table by layer thickness, see the guide “Self-Levelling Screed Consumption per m²: How Much You Need”.
Which thickness to enter and whether you need an allowance
The calculator uses one thickness for the whole area of a calculation, so enter the average layer thickness, not the thinnest point. Check for unevenness with a long straightedge: if the dips are deeper in some places, the average is greater than the thickness of the compound at the highest point. Put a much more uneven room in a separate calculation.
The calculator does not add a percentage allowance; it only rounds up to whole bags. When the calculated amount is just below full bags, as in the flat example with 199 kg, add a bag for mixing losses, the leftover in the bucket and an absorbent substrate. A substrate without primer also increases consumption, so apply primer according to the manufacturer's instructions.
The most common mistakes when calculating self-leveling compound
- Entering the thinnest point instead of the average layer thickness.
- Leaving out smaller areas: a hallway, pantry or alcove that also gets poured.
- Adding up bags from several calculations instead of kilograms.
- Buying exactly the calculated kilograms without checking how much is left in the last bag.
- A thickness outside the range the manufacturer allows for a single layer.
- Using 1.7 kg/m² per mm for a product whose technical data sheet states a different consumption.
- Calculating a thick cement screed with this calculator – it is designed for self-leveling compounds.
What else to calculate along with self-leveling compound
Levelling is usually followed by tiling: the tile calculator works out tiles, adhesive and grout, and the Levelers calculator the number of clips and wedges for flat laying. For floor finishes there are the Epoxy floor calculator and the Microcement calculator, for pipework under the screed the Underfloor heating calculator, and for a concrete base the concrete calculator. All calculations can be saved to the same project and exported as a single PDF materials list.
How long to wait before tiles and other floor coverings
Before laying tiles the typical wait is 12–24 h depending on thickness (about 2.4 h per mm), and before moisture-sensitive finishes (epoxy, microcement, stone carpet) 3–7 days. These are typical values at about 20 °C – the product data sheet takes precedence. If you save the calculation to a project, the work plan puts the levelling compound, tiles and grouting in order, with dates.
A 25 kg bag is the default size in Europe. You can choose another size in the pack menu (e.g. 50 lb in the USA); the number of bags is calculated from the same kilograms.
Frequently asked questions
How do I calculate self-leveling compound for a flat where rooms need different thicknesses?
Do one calculation for each thickness, then add up the kilograms and divide by 25: rooms of 40.8 m² at 3 mm (209 kg) and a 7.5 m² kitchen at 8 mm (102 kg) give 311 kg, which is 13 bags.
Why add up kilograms rather than the bags from individual calculations?
Each calculation rounds bags up, so the total number of bags can exceed what you need – in the example flat 14 instead of 13.
Up to what thickness does the calculator work?
The thickness can be chosen from 1 to 30 mm, in steps of 1 mm. How much may be poured in a single layer is specified by the compound's manufacturer.
What should I do at the door between rooms with different layer thicknesses?
Put a stop bar at the door line and check that the compound layer and the floor covering give the same floor height on both sides of the threshold.
Is the self-leveling compound 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.
Tools for this job
Guides: Self-Levelling Compound per m²: Calculation by Area and Layer Thickness