How to Use the Self-Leveling Underlayment Calculator
Self-leveling underlayment (SLU) is a cement-based liquid compound that flows and settles flat when poured, making it a popular choice for prepping a subfloor before installing tile, vinyl, or engineered wood. This calculator takes your floor area, pour thickness, and the product's coverage rate to give you the total weight and number of bags to order.
Coverage rates vary by manufacturer, but a common figure for cement-based SLU is roughly 8 lb per sq ft at a 1-inch pour (equivalent to a 50 lb bag covering about 27 sq ft at 1/4 inch). For the most accurate result, check your specific product's bag label or technical data sheet and enter that coverage rate, along with the actual bag weight (commonly 50 lb).
Typical pours range from a thin 1/8 inch skim coat to several inches for major low spots. If the subfloor isn't uniformly flat, use the average thickness across the area and order one or two extra bags as a buffer — running out mid-pour can leave a visible seam once the product sets.
Frequently Asked Questions
Check the bag label or technical data sheet for the coverage rate at a 1-inch pour thickness, then enter that value. If it's not listed, 8 lb per sq ft per inch is a reasonable default for common cement-based self-leveling underlayments.
Self-leveling underlayment flows to find its own level, but a subfloor with large dips or an overall slope will need more material in the low spots than a simple average-thickness estimate suggests. Checking floor elevation with a laser level before ordering helps avoid running short mid-pour.