Self-leveling concrete bags = floor area × average depth ÷ what one bag covers at that depth, rounded up. A 20 × 15 ft floor (300 sq ft) leveled ¼ in deep takes 16 bags of a 50 lb self leveler such as Quikrete Self-Leveling Floor Resurfacer, which covers 21 sq ft at ¼ in, once you add 10% for dams and low spots. The calculator does the same sum for a flat depth or for a floor that dips, and names the primer and the number of pours the depth needs.
How the self leveler is calculated
Every manufacturer prints coverage at one thickness, and coverage falls in proportion as the layer gets deeper. Half the depth covers twice the area. So the calculator works in square feet times inches:
Bags = area (sq ft) × average depth (in) × (1 + waste) ÷ (coverage at ¼ in × ¼ in)
For the Quikrete product that is 21 × ¼ = 5.25 sq ft-inches per bag. The floor is 300 sq ft × ¼ in = 75 sq ft-inches, 82.5 with 10% extra, and 82.5 ÷ 5.25 = 15.7, so 16 bags. Mixing takes about 5 quarts of water a bag, so 16 bags need 20 gallons, and the dry mix weighs 800 lb.
Floor leveler for a sloped floor: low and high spot
Few floors are level, and a leveler is poured to a level line, so it is thinnest over the highest point and thickest in the dip. Switch to "Low and high spot" and enter both depths. When the floor slopes evenly the average is halfway between them, and the calculator uses that.
Example: a 12 × 12 ft room where the high spot needs ⅛ in and the low corner ¾ in. The average is (⅛ + ¾) ÷ 2 = 0.4375 in. That is 144 × 0.4375 = 63 sq ft-inches, 69.3 with 10% extra. ARDEX K 15 covers 30 sq ft at ¼ in, so a bag gives 7.5 sq ft-inches and the room takes 9.24, so 10 bags of 55 lb. Find the depths with a laser or a long straightedge and a tape, and check a grid of points, since one deep spot drives the number.
Coverage per bag by product and depth
Sq ft per bag, from each data sheet's coverage at ¼ in scaled by depth:
| Product | Bag | ¼ in | ½ in | 1 in |
|---|---|---|---|---|
| Quikrete Self-Leveling Floor Resurfacer | 50 lb | 21 sq ft | 10.5 sq ft | 5.25 sq ft |
| Quikrete Fast-Setting Self-Leveling Floor Resurfacer | 50 lb | 21 sq ft | 10.5 sq ft | 5.25 sq ft |
| ARDEX K 15 | 55 lb | 30 sq ft | 15 sq ft | 7.5 sq ft |
| MAPEI Ultraplan 1 Plus | 50 lb | 24 sq ft | 12 sq ft | 6 sq ft |
The 1 in column is arithmetic, not a permitted pour: Quikrete's regular resurfacer goes on no thicker than ⅝ in in one layer, and the data sheets of the other three allow 1½ in. MAPEI's own table prints 24, 12 and 6 sq ft for ¼, ½ and 1 in, which matches.
How thick can self-leveling concrete go, and how thin
- Quikrete Self-Leveling Floor Resurfacer: from ⅝ in down to a feather edge, in layers no thicker than ⅝ in, with primer between layers.
- Quikrete Fast-Setting: up to 1½ in in a layer, ¼ in minimum where there is heavy traffic; extendable with pea gravel past 1½ in.
- ARDEX K 15: 1½ in neat and up to 5 in with aggregate, an average of at least ¼ in, and ⅛ in over the highest point.
- MAPEI Ultraplan 1 Plus: 1/16 in to 1½ in a lift, and 1/16 in minimum over the highest point.
The calculator counts the lifts from your deepest point and warns when your low spot is thinner than the sheet allows.
Primer for self-leveling concrete
The primer keeps the porous slab from pulling water out of the leveler before it flows. Quikrete specifies 1 part Concrete Bonding Adhesive to 2 parts water, brushed or sprayed with no puddles, dry to the touch in 1 to 2 hours, and two coats on very porous concrete. ARDEX uses P 51 diluted 1:1 with water and a push broom on absorbent concrete; for sealed or burnished concrete it names other primers. Prime the whole floor, so the primed area equals the floor area.
What else you need before you pour
Fix holes deeper than 1 inch first, seal every gap where leveler could leak, and dam the edges. Quikrete stays fluid for about 20 minutes, ARDEX flows about 10, so mix one bucket per bag and pour continuous strips. Do not pour below 50°F, and keep the floor out of sun and drafts. Test the slab for moisture with a taped poly sheet before flooring goes down.
What goes on top
Once cured, the leveled floor takes tile, sheet or plank flooring, or an epoxy coating. For a new pour instead of a leveled old one, size it with the concrete slab calculator, compare bags in the concrete bag calculator, and get the room's area from the square footage calculator. Every concrete and masonry tool is in the concrete and masonry calculators.
This self leveling compound calculator uses the product yield, so the bag count matches the brand you pick.