How the self-leveling calculator works
Floor levelers are cement- or gypsum-based powders that flow like thick cream and find their own level. Makers state how much dry powder is used per square metre for each millimetre of depth, and that number, not the bag weight, is the key to an accurate order. The calculator multiplies the floor by the average depth and by that consumption, then adds 10% for the compound that runs into gaps, stays in the bucket and flows under door frames.
Powder = area × average depth × consumption × 1.10 · Bags = powder ÷ bag weight, rounded upIn metric, area in m² times depth in mm gives litres directly, which is also shown as the poured volume. In US units the consumption is given per inch of depth, so 1/4 in is entered as 0.25.
Finding the average depth
A floor that needs leveling is by definition uneven. Lay a long straightedge or use a laser, and measure the gap at a grid of points about every metre (3 ft). Add the readings and divide by their number. If a kitchen slopes steadily from 2 mm at one wall to 14 mm at the other, the average is 8 mm, and ordering for 14 mm everywhere would waste almost half the bags.
Worked example
A 4 m × 3.5 m kitchen is 14 m². With an average depth of 6 mm and a consumption of 1.6 kg/m² per mm, it takes 14 × 6 × 1.6 = 134.4 kg of powder, and 147.8 kg with the allowance. That is 5.9 bags of 25 kg, so six bags, making about 84 litres of mixed compound. In US units, a 13 ft × 11.5 ft room (149.5 ft²) at 1/4 in and 8.3 lb/ft² per inch needs 149.5 × 0.25 × 8.3 × 1.10 = 341 lb, which is seven 50 lb bags.
What one bag covers
| Bag | Depth | Covers about |
|---|---|---|
| 25 kg | 3 mm | 5.2 m² |
| 25 kg | 5 mm | 3.1 m² |
| 25 kg | 10 mm | 1.6 m² |
| 25 kg | 20 mm | 0.8 m² |
| 50 lb | 1/8 in | 48 ft² |
| 50 lb | 1/4 in | 24 ft² |
| 50 lb | 1/2 in | 12 ft² |
Figures assume 1.6 kg/m² per mm (8.3 lb/ft² per inch) and no waste.
Pouring tips
- Prime first. Unprimed concrete sucks water out of the mix, causing pinholes and weak spots.
- Respect the depth range. Most products work between about 2 and 30 mm per pour; deeper fills need a product rated for it, or added aggregate if the data sheet allows.
- Measure the water exactly. Extra water makes it flow nicely but causes dusting and cracks.
- Organise the team. Working time is often 15–30 minutes, so one person mixes while another pours and spreads with a gauge rake and spiked roller. Keep a wet edge.
- Seal edges and gaps. Fit a foam strip at the walls and plug holes, or the liquid will disappear into the floor below. Timber subfloors usually need a fibre-reinforced product and metal lath; follow the maker.
A reproducible calculation with complete inputs
For a reproducible self-leveling compound calculator example, use the metric input system and enter Floor length: 4 m; Floor width: 3.5 m; Average depth: 6 mm; Consumption: 1.6 kg/m² per mm; Bag size: 25 kg bag. These settings describe one specific scenario, not a new default for every job. The result follows the method and allowances already explained above. Keep the entire set of values when comparing it with a hand calculation; omitting a selected material or an allowance can change the result even when the dimensions match. The following rows show the unrounded calculation values alongside the precision used by the interface.
| Result | Calculation value | Displayed value | Unit |
|---|---|---|---|
| Self-leveler needed | 147.84 | 148 | kg |
| Bags to buy | 6 | 6 | bags |
| Poured volume | 84 | 84.0 | L |
| Floor area | 14 | 14.0 | m² |
How should I prepare these entries?
Floor length: enter the value in m. Floor width: enter the value in m. Average depth: Average, not deepest point. 1/8 in = 0.125, 1/4 in = 0.25, 1/2 in = 0.5. Consumption: On the bag or data sheet: usually 1.5–1.8 kg/m² per mm (about 7.8–9.4 lb/ft² per inch). Bag size: choose among 25 kg bag, 20 kg bag, 50 lb bag, 40 lb bag. Choose the unit system before transferring your measurements. A depth, length, area and coverage can have different field units even within one system. Read each label individually rather than entering the same unit convention in every box. Optional openings or allowances should describe your actual scenario instead of being silently left at a sample value. The worked inputs above identify exactly which selections produced the table.
Frequently asked questions
How many bags of self-leveling compound do I need?
Multiply the floor area by the average depth and the consumption. A 10 m² room at 5 mm needs about 80 kg plus 10%, so four 25 kg bags.
How much does a 50 lb bag of self-leveler cover?
Roughly 48 ft² at 1/8 in and 24 ft² at 1/4 in, based on a typical 8.3 lb per ft² per inch.
How thick can self-leveling compound be poured?
Most general-purpose levelers take 2–30 mm (about 1/16 to 1 1/4 in) per pour. Deeper areas need a deep-fill grade or a first layer to build up.
How do I calculate the average depth of an uneven floor?
Measure the gap under a straightedge or laser line at regular points across the room, add them together and divide by the number of readings.
How long before I can walk on self-leveling compound?
Many products take light foot traffic after 2–4 hours, but tiles or flooring usually wait from one day to several days depending on depth; check the bag.