Self-Leveling Compound Calculator
Estimate the bags of self-leveling compound to pour a subfloor flat, from the area, the average pour depth and how much one bag yields.
Calculator
Leveling 120 sq ft to an average 0.50 in needs about 6 bags (a 50-lb bag yields roughly 10 sq ft·in). Use the average depth across the floor. Confirm the yield on your bag — coverage varies by product.
Self-leveling compound (SLC, or “self-leveler”) is a cement-based slurry you mix and pour over a subfloor; it flows out and cures to a flat, hard surface ready for tile, vinyl, engineered wood or carpet. It is the fix for a floor that dips, humps or slopes — the flatness a modern floor needs and that plain underlayment cannot deliver.
Coverage is measured in square-feet-inches (sq ft·in): the area times the pour depth. A 50-lb bag that yields about 10 sq ft·in covers 10 sq ft at 1 inch, 20 sq ft at ½ inch, and so on. Because floors are rarely uniform, the honest input is the average depth across the whole floor, not the deepest low spot. For coverage typicals see the coverage table; the guide Subfloor prep & self-leveling: how much compound do I need walks the whole job.
Formula
bags = ceil( area_sqft × avg_depth_in ÷ bag_yield_sqft_in )
- area_sqft × avg_depth_in — the coverage you need, in square-feet-inches.
- bag_yield_sqft_in — labeled yield per bag (a 50-lb bag ≈ 10 sq ft·in).
- ceil() — round up to whole bags.
Use the average depth: estimate it by checking several low spots against a long straightedge or laser and averaging their fill. A feather-thin skim over most of the floor with a couple of deeper lows averages out to a small number — do not enter the deepest reading.
Worked example
A 120 sq ft floor, average pour depth ½ inch (0.5 in), a 50-lb bag yielding 10 sq ft·in:
120 × 0.5 = 60 sq ft·inceil(60 ÷ 10) = ceil(6.0) = 6 bags
Six bags is the on-paper number. Mix and pour fast — most compounds stay workable for only 10–20 minutes — so having a spare bag on hand keeps a batch from setting up short. Prime the subfloor first: an unprimed slab pulls water out of the mix and ruins the flow.
Pouring a level floor
Average depth is the whole game. The single biggest error is entering the deepest low spot instead of the average across the floor. Map the highs and lows against a straightedge, and if the floor only needs a thin skim over most of its area with a few deeper dips, the average may be an eighth or a quarter inch — far less compound than the worst spot suggests. Overwrite the ½-inch default with your own reading.
Prime, contain and mix in order. Bare concrete and wood both need the primer the maker specifies, or the compound flash-dries and cracks. Dam any doorways, floor drains and gaps so the slurry does not run off. Mix to the stated water ratio — too much water weakens the cured surface and causes it to dust. Bag yield varies a lot by product and by how thick you pour, so confirm the sq ft·in figure on your bag rather than trusting the 10 default.
This is prep, not structure. Self-leveler evens a surface for the finished floor; it does not add structural strength or fix a bouncy, under-built subfloor. A springy floor is a framing question for a qualified builder, not a bag-count question. Once the pour is flat and cured, size any underlayment or subfloor sheets on top of it.
Frequently asked questions
How much self-leveling compound do I need for 120 sq ft?
At an average ½-inch pour and a bag yielding 10 sq ft·in: 120 × 0.5 = 60, then ceil(60 ÷ 10) = 6 bags. Buy a spare, because the mix sets in minutes and you cannot pause mid-pour.
Should I use the average depth or the deepest spot?
The average across the whole floor. Entering the deepest low spot hugely overstates the bags: a thin skim over most of the area with a few deeper dips averages to a small depth. Check several points with a straightedge and average them.
What does “sq ft·in” mean?
Square-feet-inches — area times depth. A bag yielding 10 sq ft·in covers 10 sq ft at 1 inch, or 20 sq ft at ½ inch. It lets one number describe a bag's coverage at any thickness.
Do I have to prime before pouring?
Almost always yes. Unprimed concrete or wood pulls water out of the compound, which flash-dries, cracks and bonds poorly. Use the primer the manufacturer specifies and let it tack up before you pour.
Can self-leveler fix a bouncy floor?
No. It flattens a surface; it does not stiffen framing. A springy floor is a joist/structure question for a qualified builder and local code — the compound only prepares the top surface for the finished floor.
How thick can I pour in one go?
That is set by the product — many pour from a feather edge up to about ½ to 1 inch neat, with aggregate needed for deeper fills. Check your bag; deeper than its rated maximum needs a different mix or multiple lifts.