Subfloor Leveling Calculator
Calculate self-leveling compound quantities, primer needs, curing time, and cost for subfloor preparation.
About this calculator
Bags Needed comes from a weight budget, not a coverage-rate lookup: the engine multiplies Floor Area by Average Depression to get a fill volume, converts it to weight at a fixed self-leveling compound density of 130 lb/cu ft, and divides by Bag Weight, rounding up so you never come up short. That means Average Depression and Floor Area both push the bag count up in direct proportion, while a heavier Bag Weight pushes it down — buying 80 lb bags instead of 50 lb bags means fewer bags for the same job, even though the total pounds of compound purchased stays about the same. Maximum Depression plays no role in Bags Needed at all; it only sets Curing Time, since the deepest pour point is what determines how long the whole floor needs before it's ready to walk on (roughly 1.5 hours per 1/8-inch at that deepest spot).
Compound Coverage is included as a field for cross-checking against your product's own label, but this calculator's bag count comes from the density-and-weight math above rather than from a coverage-per-bag rating, so changing it will not move Bags Needed. Primer Needed assumes one gallon per 300-400 sq ft and is independent of depression depth.
Inputs
Results
Bags Needed
17
Estimated Cost
$629.40
≈ 7 nice dinners out
How to Use This Calculator
- Enter the total floor area requiring leveling in square feet.
- Measure the maximum depression (deepest low spot) with a 6-foot straightedge and enter in inches.
- Enter the average depression depth across the floor.
- Enter the bag weight from the product label — Compound Coverage is included for your own cross-check but does not change the bag count.
- Review the estimated bags needed, compound volume, and total weight to plan material orders.
How the result changes with Bag Weight
| Bag Weight | Bags Needed | Estimated Cost |
|---|---|---|
| 25 | 33 | $1,189.40 |
| 38 | 22 | $804.40 |
| 75 | 11 | $419.40 |
| 100 | 9 | $349.40 |
What each input means
- Floor Area
- Total floor area requiring leveling.
- Maximum Depression
- Deepest low spot measured with a straightedge.
- Average Depression
- Average depth of depressions across the floor.
- Compound Coverage
- Coverage per bag at 1/8 inch depth (check product label).
- Bag Weight
- Weight of each bag of self-leveling compound.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersFloor Area = 300, Maximum Depression = 0.5, Average Depression = 0.25, Compound Coverage = 25 = 5 input(s) provided
- Calculate Bags NeededBags Needed17 = 17
- Calculate Estimated CostEstimated Cost629.4 = $629.4
- Calculate Compound VolumeCompound Volume6.25 = 6.25
- Calculate Total Compound WeightTotal Compound Weight850 = 850
Engine last updated . Checked against 3 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why doesn't changing Compound Coverage change the Bags Needed?
Because this calculator sizes bags from a weight budget — floor area times average depression converted to pounds at a fixed 130 lb/cu ft compound density, then divided by bag weight — rather than from a coverage-per-bag rating. Compound Coverage is shown for reference against your product label, but the bag count itself doesn't use it.
Why does Maximum Depression not affect Bags Needed?
Bags Needed is driven by the average depth across the whole floor, since that's what determines total compound volume. Maximum Depression instead sets Curing Time, because the single deepest pour point is what takes longest to fully cure before the floor can be walked on.
Does buying heavier bags save money?
Not directly — Bags Needed drops when Bag Weight goes up, since fewer heavier bags cover the same total pound requirement, but Estimated Cost uses a flat $35-per-bag rate regardless of bag size, so the dollar savings from this calculator come only from buying fewer bags, not from any per-pound discount.
How is Curing Time calculated?
It's about 1.5 hours for every 1/8 inch of Maximum Depression, since the deepest point in the pour is the last to fully set. A floor with a 1-inch deep low spot needs roughly 12 hours before it's ready for foot traffic, even if most of the floor is much shallower.
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