About

Internal flooring projects often require a higher degree of precision than outdoor slabs. Whether you are pouring a standard concrete screed for a basement or applying a self-leveling compound to prepare a subfloor for tiling, accurate material calculation is essential. Running short on self-leveling compound mid-pour is particularly disastrous, as it cures quickly and leaves visible ridges.

This calculator distinguishes between standard floor mixes and specialized compounds. Self-leveling materials have significantly different densities and coverage rates compared to standard concrete. Getting this right ensures a perfectly flat finish without the expensive need to grind down high spots or buy emergency buckets of expensive compound.

Formulas

The core calculation determines the mass required based on volume and specific material density.

Volume:
V = Area × Thickness

Mass Required:
M = V × Density

Bag Count:
Bags = MWeight_bag

Note: Self-leveling compounds are often sold by coverage (e.g., "50 sq ft at 1/8 inch"). This tool converts those specs into a universal volume-to-mass standard.

Reference Data

Material Type	Typical Density	Min Thickness	Typical Application
Standard Concrete	2,400 kg/m³	50 mm (2 in)	Basement floors, Structural slabs
Sand/Cement Screed	2,000 kg/m³	35 mm (1.4 in)	Underfloor heating coverage
Self-Leveling Compound	1,700 kg/m³	3 mm (0.1 in)	Surface smoothing, Tile prep
Lightweight Concrete	1,400 kg/m³	N/A	Upper floor structural relief
Anhydrite Screed	2,100 kg/m³	35 mm (1.4 in)	Large area pump-able screed
Epoxy Resin	1,100 kg/m³	0.5 mm	Garage/Industrial coatings
Fiber Reinforced Concrete	2,400 kg/m³	100 mm (4 in)	High traffic internal zones
Polymer Modified Screed	2,150 kg/m³	10 mm (0.4 in)	Thin bonded screeds

Frequently Asked Questions

Generally, no. Standard concrete relies on aggregate (stone) for strength and requires a minimum thickness of about 2 inches (50mm) to prevent cracking. For layers thinner than this, use a sand-cement screed or a dedicated self-leveling compound.

Standard concrete is dense (~2400 kg/m³), while self-leveling compounds are lighter (~1700 kg/m³) due to different polymers and fillers. Using a concrete calculator for self-leveler will result in over-ordering by nearly 30%.

If the floor dips and rises, measure the depth at multiple points (at least 5-10 spots). Calculate the average depth and use that as your thickness input. Always add 10-15% safety margin for uneven substrates.

No. You buy the dry material by weight (bags). The water added evaporates during the curing process, so the final volume is roughly determined by the dry bulk density and the hydration reaction, but purchasing is always based on dry weight.

A bonded screed uses a bonding agent to stick directly to the concrete base. An unbonded screed sits on a plastic membrane (damp proof membrane) separating it from the base. Unbonded screeds generally need to be thicker (min 50mm) to support themselves.