Self-Leveling Compound Calculator
Find out how many 50-lb bags of self-leveling underlayment a floor needs at your pour depth, plus the primer to seal it first.
Coverage is a depth problem
Self-leveling underlayment is sold against one benchmark figure: a 50-lb bag covers about 24 sq ft at 1/4 in deep — the mid-point of the major brands' published charts. Everything else is proportion: halve the depth and a bag goes twice as far; double it and buy twice as many. The calculator scales the benchmark to your average depth and area, and adds the primer, because unprimed concrete drinks the water out of the pour and ruins both the flow and the bond.
Bags = area × (your depth ÷ 1/4 in) ÷ 24 sq ft per bag · Primer ≈ 1 gal per 500 sq ft
Example: 100 sq ft at an average 1/4 in needs 100 ÷ 24 = 4.17 bags exactly — 5 bags with the 10% allowance — and 1 gallon of primer.
Average depth, honestly taken
The depth that matters is the pour's depth at its deepest planned point minus nothing — level means filling to the highest spot on the floor, so the average depth over the room is typically half to two thirds of the worst dip plus your minimum cover over the high point (most products want at least 1/8 in over the peak). Survey the floor with a long straightedge, mark the dips, and average generously: running out mid-pour, with a wet edge setting, is the one failure this material does not forgive.
Most self-levelers also have a maximum single-pour depth — commonly 1/2 to 1 in, with special deep-pour products beyond that. If your average comes out over your product's limit, plan two lifts and let the calculator count the total; the bags are the same, the schedule is not.
Frequently asked questions
How deep can I pour self-leveler in one go?
Standard products allow about 1/2 to 1 in per lift; deep-fill versions go to 2 in or more, sometimes with aggregate added. Check your bag — exceeding the limit risks cracking and a soft, dusty surface that never reaches strength.
Do I really need the primer?
Yes. Primer seals porous concrete so the pour keeps its water long enough to flow and cure, and it is the bond layer the manufacturer warrants. Skipping it is the leading cause of delamination — the floor sounds hollow within a year.
Can self-leveler be the finished floor?
Underlayments are made to be covered — by tile, plank or carpet. Wear-rated topping products exist for a finished concrete look; they are a different, harder material and their coverage per bag is lower. These figures are for underlayment under a floor covering.
How long before I can tile or lay flooring over it?
Most underlayments take foot traffic in 3–4 hours and tile the next day; moisture-sensitive flooring (glued wood, sheet vinyl) usually waits 2–3 days. The bag's schedule governs — depth and room humidity stretch it.
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