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Self-Leveling Underlayment (SLU) Volume Calculator

Calculate the self-leveling underlayment volume needed to correct subfloor roughness before flooring installation.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

SLU volume needed

39.63 gal

Check your inputs

Actual SLU consumption depends on subfloor roughness/low spots — an uneven subfloor will consume more material than this average-depth estimate suggests. Order 10-15% extra for irregular subfloors.

For the dimensions entered, expect a slu volume needed of 150. Moderate confidence — sound arithmetic, but allow for the variation any real site introduces. Set for United States against IRC 2024. The market selector changes both the units and the code cited.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • SLU volume = floor area × average pour depth, the standard method for a self-leveling compound poured at a roughly uniform average thickness

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Frequently asked questions

Why use an average depth instead of a fixed pour thickness?
Self-leveling underlayment is designed to flow and self-level, so it naturally sits thicker over low spots and thinner over high spots. An average depth across the whole floor gives a more realistic total volume than assuming a single uniform thickness.
Should I order extra material beyond this estimate?
Yes — an uneven subfloor with significant low spots will consume more material than an average-depth estimate suggests. Ordering 10-15% extra is a reasonable allowance for irregular subfloors.
How do I estimate my subfloor's average pour depth?
Check several points across the floor with a straightedge and measure the gap to identify high and low spots, then estimate a reasonable average depth that accounts for the low spots needing more material.