CALCULATOR
Self-levelling compound calculator
Estimate bags required by area and thickness. Built for floor levelling over concrete, timber subfloors and screed correction across the Hunter.
Self-levelling compound consumption scales linearly with area and thickness. A 30 m² pour at 5 mm needs roughly 240 kg; the same area at 10 mm needs 480 kg. The calculator below estimates kilograms required by area and thickness, and recommends the right pack count for your job.
How self-leveller coverage is calculated
Most cement-based self-levellers cover at approximately 1.6 kg per square metre per millimetre of thickness. To work out total kilograms required:
- Area × thickness × 1.6 = kg of dry product needed
- Round up to the next whole bag, then add one extra for unexpected dips
- For pours over 30 m², add two spare bags — running out mid-pour breaks the join line
Self-levellers have a strict working time window — usually 20–30 minutes from mixing. On big pours you’ll need a continuous mixer or two crews mixing in parallel, otherwise the leading edge skins before the trailing edge is poured.
Typical coverage rates we use
| Thickness | kg / m² | 30 m² pour | 50 m² pour |
|---|---|---|---|
| 3 mm (feather) | 4.8 kg | 144 kg (8 × 20 kg) | 240 kg (12 × 20 kg) |
| 5 mm (standard) | 8.0 kg | 240 kg (12 × 20 kg) | 400 kg (20 × 20 kg) |
| 10 mm (deep correction) | 16.0 kg | 480 kg (24 × 20 kg) | 800 kg (40 × 20 kg) |
| 20 mm (heavy correction) | 32.0 kg | 960 kg (48 × 20 kg) | 1600 kg (80 × 20 kg) |
Substrate prep is 90% of the job
Self-levellers are unforgiving of bad substrate prep. The pour looks foolproof — and on a properly primed, clean, mechanically prepared slab it more or less is. On a contaminated slab without proper bond test and primer, the leveller debonds inside 12 months and lifts under load.
Bond test
Tape polythene to the slab for 24 hours. Condensation underneath = the slab is releasing moisture. Pouring on that = guaranteed debond.
Mechanical prep
Grind or shotblast to CSP 2–3. Removes surface contamination and gives the leveller a profile to mechanically key into.
Primer
Porous primer on porous slabs. Seals porosity, prevents mix water from being drained into the slab, creates a clean bond surface.
Our most common self-levelling substrate mistakes covers the four prep failures we see most often.
Order one spare bag — always
The single most expensive mistake on a self-levelling job is running short mid-pour. The leading edge skins, the join line is visible forever, and on tile finishes the bond can fail above it. A spare 20 kg bag is roughly $35 retail; the cost of stopping the job to source one is at least an hour of crew time plus delivery — and frequently the difference between a one-day pour and a two-day pour.
For pours over 30 m², bring a second mixer and a second labourer. Self-levellers have a 20–30 minute working window; one crew can lay maybe 15 m² in that window before the join lines start to show.
Frequently asked questions
How thick can I pour self-leveller in one pass?
Most cement-based self-levellers pour up to 30 mm in one pass. For thicker corrections, use a deep-pour formulation or pour in lifts with a primer between coats. The 1.6 kg/m²/mm rate is the same regardless of thickness — but mix water ratio and working time both vary, so check the TDS.
Can I tile or vinyl over self-leveller the next day?
Foot traffic at 4 hours, tile at 24 hours, vinyl typically at 48–72 hours pending moisture test. Always confirm against the TDS for your product. Pouring on a wet substrate and tiling too soon are the two most common callbacks.
Do I need to prime before self-levelling?
Yes. Porous primer on porous slabs; non-porous primer on dense substrates like terrazzo or ceramic. The primer also acts as a visual check — if it beads up rather than absorbing, the substrate has surface contamination that needs to be ground off.
Can I pour self-leveller over timber subfloors?
Yes, with the right primer and a separation layer for thick pours. Timber subfloors flex; the leveller needs to be installed in a way that decouples it from substrate movement. Talk to us before ordering — we’ll match the product to the deflection.
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