Floor Leveling Compound Calculator
This free floor leveling compound calculator sizes a self-leveling underlayment (SLU) pour the way the manufacturer’s own chart does — not a blended, made-up industry rate. Bag weight and coverage vary enough between products (30 to 55 lb bags, roughly 0.46 to 0.75 sq ft per pound at 1/4") that averaging them would misrepresent any single one, so this calculator keeps ARDEX K 15, MAPEI Novoplan 2 Plus, MAPEI Ultraplan Easy, Custom LevelQuik RS, Custom LevelLite, and Henry 555 as separate, distinct products, each with its own transcribed technical-data-sheet chart.
It also handles what a bag count alone would miss: the primer coat almost every SLU requires (coverage depends on both the substrate — porous concrete, non-porous, or wood — and the dilution ratio, each cited to its own manufacturer data sheet), and a double-prime option for very absorbent concrete. Depths between a product’s published points are interpolated from the manufacturer’s own chart rather than assumed perfectly linear, since a couple of these charts have small, real deviations from a straight line. Ask for the depth as an average across the whole floor, not just the gap at the low point — that’s how the manufacturers themselves define it.
When your target depth falls below a product’s rated minimum, it tells you to use a trowel-applied patch instead; when it exceeds even the aggregate-extended maximum, it says so rather than guessing a number no manufacturer publishes. Sizing only — no pricing, no signup.
Floor Leveling Compound Calculator
How many bags of self-leveling underlayment do you need before laying finish flooring? Bags and primer by product, depth, and substrate — from manufacturer data sheets, not a blended rate. Free, no signup.
Floor area & depth
Use the AVERAGE pour depth across the whole floor, not just the gap at the lowest point.
Product
Coverage is product-specific — bag weight and yield vary enough between brands that a blended rate would misrepresent any one of them.
Primer
Nearly every self-leveling compound requires a primer coat first.
Coverage chart — MAPEI Novoplan 2 Plus (50 lb bag)
Manufacturer-published sq ft per bag by depth. Depths between these points are interpolated; the chart is close to but not perfectly linear.
| Depth | Sq ft per bag |
|---|---|
| 0.25" | 24 |
| 0.5" | 12 |
| 0.75" | 9 |
| 1" | 6 |
Source: MAPEI TDS MK 3000067 (Edition Aug 29, 2023).
Why "average depth," not the low point
The pour is flat on top, but the subfloor underneath almost never is — so the actual depth varies across the floor. A rated minimum over the high point (often just ⅛") typically works out to a noticeably deeper average everywhere else, which is the number this calculator actually wants.
Calculation Formulas
When the requested depth matches a depth the manufacturer actually publishes, the calculator uses that exact figure — not a derived or averaged one.
Example:
200 sq ft at 3/4" with MAPEI Novoplan 2 Plus (9 sq ft/bag published, not the linearly-scaled 8): 200 ÷ 9 = 22.2 → 23 bags.
Manufacturer coverage charts are close to linear but not exact — interpolating between real published points is more accurate than assuming a single ratio holds across the whole range.
Example:
0.375" falls between MAPEI's published 0.25" (24 sq ft/bag) and 0.5" (12 sq ft/bag) → interpolated 18 sq ft/bag.
ARDEX K 15 and Henry 555 publish only ONE depth each (1/4" and 1/8" respectively). Every depth outside that one point is linearly scaled and flagged as DERIVED, not itself a manufacturer-printed number — justified by the fact that every multi-point product in this catalog confirms the linear relationship.
Example:
ARDEX K 15 publishes 30 sq ft/bag at 1/4". At 1/2": (30 × 0.25) ÷ 0.5 = 15 sq ft/bag (derived).
Coverage rate depends on substrate (porous concrete, non-porous, or wood) and dilution — each has its own manufacturer-published rate. A very absorbent substrate gets two coats (double-prime).
Example:
200 sq ft of porous concrete at 500 sq ft/gal (ARDEX P 51, 1:1): 0.4 → rounded up to 0.5 gal; double-primed, 1 gal.
Standard Constants
| Constant | Value | Description |
|---|---|---|
| Coverage is product-specific | Never averaged | Bag weight (30/40/50/55 lb) and yield vary enough between products that a blended rate would misrepresent any single one — every product's own published figure is used. |
| ARDEX K 15 | 30 sq ft / 55-lb bag @ 1/4" | Min 1/8" over the high point; max 1.5" neat, 5" with pea-gravel aggregate (yield not published for the aggregate mix). |
| MAPEI Novoplan 2 Plus | 24/12/9/6 sq ft per 50-lb bag @ 1/4"/1/2"/3/4"/1" | Min 1/8" over the high point; max 1" single lift. |
| MAPEI Ultraplan Easy | 24/12/9/6/4/3 sq ft per 50-lb bag @ 1/4" through 2" | Min 1/16" over the high point (thinnest-rated product in this catalog); max 2" single lift. |
| Custom LevelQuik RS | ~47/23.5/11.75/5.9/3.9 sq ft per 50-lb bag @ 1/8" through 1.5" | Values are midpoints of the manufacturer's own published ranges (e.g. 46-48 sq ft → 47). Featheredge to 1.5" per pour. |
| Custom LevelLite | ~45/22.5/11.25/5.6/2.8 sq ft per 30-lb bag @ 1/8" through 2" | Lightweight formula — covers more per pound than standard-density products. Featheredge to 2" per pour. |
| Henry 555 LevelPro | 43 sq ft / 40-lb bag @ 1/8" (only published depth) | Min 1/8" over the high point; max 1.5" neat, 5" with pea-gravel aggregate. |
| Average depth, not minimum | Ask for the average | Per ARDEX's own guidance: a 1/8" minimum over the high point "typically results in an average thickness of 1/4" or more over the entire floor" — this calculator asks for that average, not the thinnest spot. |
| Waste allowance | 5–10% (MAPEI's own calculator) | No SLU manufacturer's TDS specifies a waste factor — this figure comes from MAPEI's own online calculator guidance, not an industry standard, and is user-adjustable. |
| Deflection limit | L/360 (L/720 under stone) | Cited by MAPEI, Custom, and USG alike — leveling compound is not a structural fix; a bouncy or undersized floor must be corrected first. |
Note: All calculations include appropriate waste factors based on project complexity and material type. Results are estimates and should be verified by professionals before purchasing materials.
Manufacturer Technical Data Sheets (TDS) — Coverage(ARDEX K 15; MAPEI Novoplan 2 Plus / Ultraplan Easy; Custom LevelQuik RS / LevelLite; Henry 555)
View StandardEach product's own published sq-ft-per-bag chart by depth — the primary source for every bag-count figure this calculator returns. Charts are estimates per every manufacturer's own disclaimer ("coverage varies with substrate texture").
Key Requirements:
- •Coverage read from the product's own chart, not a blended rate
- •Depths between published points are interpolated, not assumed linear
- •Single-point products (ARDEX K 15, Henry 555) are linear-scaled and flagged as derived beyond their one published depth
Primer TDS — ARDEX P 51, MAPEI ECO Prim Grip, Henry 554(Manufacturer TDS, by substrate)
View StandardPrimer coverage is substrate- and dilution-dependent: porous concrete primers are diluted (roughly 400–800 sq ft/gal); non-porous primers are used undiluted at a lower rate (150–300 sq ft/gal).
Key Requirements:
- •Porous concrete: diluted 1:1, ~500 sq ft/gal (ARDEX P 51 basis)
- •Non-porous (tile, VCT, cured adhesive): undiluted, ~225 sq ft/gal (MAPEI ECO Prim Grip basis)
- •Wood subfloor: undiluted, ~500 sq ft/gal (Henry 554 basis)
- •Very absorbent substrates get a double-prime (two coats)
Deflection & Substrate Requirements(MAPEI / Custom / USG installation guidance)
View StandardSelf-leveling compound is a flooring underlayment, not a structural repair. All major manufacturers cap allowable subfloor deflection and specify wood-subfloor reinforcement (metal lath, minimum plywood thickness) before pouring.
Key Requirements:
- •L/360 maximum deflection (L/720 under natural stone)
- •Wood subfloors: 3/4" T&G plywood/OSB minimum (product-dependent), often with galvanized metal lath stapled ~6" o.c.
- •Loose, deflecting, or damaged subfloor areas must be structurally corrected first — not leveled over
Finish-Flooring Flatness Targets (for context)(ASTM F710 (resilient); ANSI A108.02 (tile); NWFA guidelines (wood))
View StandardThe flatness tolerances leveling compound is trying to achieve, cited through trade publications and manufacturer references since the standards themselves are paywalled at their source.
Key Requirements:
- •Resilient flooring (ASTM F710): 3/16" in 10 ft, 1/32" in 12"
- •Tile (ANSI A108.02): 1/4" in 10 ft (or 1/8" in 10 ft for large-format tile with an edge ≥15")
- •Wood flooring (NWFA): 3/16" in 10 ft glue-down/short-fastener; 1/4" in 10 ft for longer fasteners
Standards Disclaimer: Standards and codes are subject to periodic updates. Always verify current requirements with local building authorities and professional engineers before beginning construction. Links provided are for reference only.
Product Selection
Standard-density vs. lightweight
Standard-density SLUs (ARDEX K 15, MAPEI, Custom LevelQuik RS) cover roughly 0.46–0.55 sq ft per pound at 1/4". Lightweight formulas like Custom LevelLite cover closer to 0.75 sq ft per pound — fewer, lighter bags for the same floor, at a different price point and cure profile.
Regional Examples:
Depth vs. Product Choice
Not every product covers every depth
Minimum and maximum rated depths differ by product: MAPEI Ultraplan Easy is rated down to 1/16" and up to 2" neat, while MAPEI Novoplan 2 Plus tops out at 1". Choosing a product that doesn't cover your target depth means either switching products or extending with manufacturer-specified pea-gravel aggregate (which this calculator won't estimate bags for — no manufacturer publishes an aggregate-mix yield).
Regional Examples:
Substrate Type
Concrete vs. wood vs. non-porous
Primer choice, dilution, and coverage all change with substrate. Wood subfloors additionally need mechanical reinforcement (metal lath) that concrete substrates don't, and board/plank subfloors typically need an added plywood layer before pouring.
Regional Examples:
Before You Build
- •Contact your local building department for specific requirements
- •Verify frost line depths, wind zones, and seismic requirements for your area
- •Check if permits are required and schedule required inspections
- •Consult with a local contractor familiar with local codes
Plan disposal before you start
Smaller jobs still produce more debris than a few trash bags can hold. Check what's allowed in a dumpster and which disposal option fits the scope.
See disposal options →
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How to Use This Calculator
- Enter your floor’s length and width, and the average pour depth in inches — the average across the whole floor, not just the low point.
- Pick a self-leveling compound product — coverage is calculated from that product’s own published chart.
- Choose your substrate (porous concrete, non-porous, or wood) for the primer calculation, and check the double-prime box if the concrete is very absorbent.
- Adjust the waste allowance if your room has a lot of cutting-in (the 10% default follows a manufacturer’s own calculator guidance, not a code requirement).
- Click Calculate for the bag count, primer gallons, and product-specific installation notes.
Why Coverage Is Never One Number
Self-leveling underlayment coverage charts all follow the same basic physics — double the depth, halve the coverage — but the actual sq-ft-per-bag figure a manufacturer publishes depends on that product’s specific formulation and bag weight, and no two products on the market use quite the same numbers. A 55 lb ARDEX K 15 bag, a 50 lb MAPEI or Custom bag, and a 30 lb lightweight Custom LevelLite bag all cover different areas at the same depth, so a single blended "average" rate would be wrong for every product it wasn’t built from. This calculator keeps each product’s own chart intact, interpolates between the manufacturer’s actual published depths rather than assuming a straight line across the whole range, and tells you plainly when a depth falls outside what any manufacturer has tested and published — rather than inventing a number for that gap.
Frequently Asked Questions
How many bags of self-leveling compound do I need?
It depends on the product, the average depth, and your floor area — coverage isn't one universal number. At a common 1/4" average depth, a 50-lb bag of MAPEI Novoplan 2 Plus or Custom LevelQuik RS covers about 23–24 sq ft, a 55-lb bag of ARDEX K 15 covers about 30 sq ft, and a 30-lb bag of lightweight Custom LevelLite covers about 22.5 sq ft. For a 200-sq-ft room at 1/4" with 10% waste, that's roughly 10 bags of a standard 50-lb product. Enter your product, area, and average depth and this calculator reads the manufacturer's own chart for you.
What's the difference between self-leveling compound and a floor patch?
Self-leveling underlayment (SLU) is a pourable, self-flowing product rated for a minimum depth — typically 1/16" to 1/8" over the highest point — and it's designed to flow into a flat, continuous plane across a whole floor. A patch or skim-coat product like ARDEX Feather Finish is trowel-applied, doesn't self-level, and handles true feather-edge repairs (down to essentially zero thickness) that an SLU's minimum-depth rating can't reach. If your target depth is below your chosen SLU's rated minimum, use a patch product instead — this calculator flags that case rather than returning an unreliable bag count.
Do I need to prime before pouring self-leveling compound?
Yes — nearly every manufacturer requires a primer coat first, and skipping it risks pinholing, poor bond, or the pour drying too fast at the edges. Coverage and dilution depend on the substrate: porous concrete typically gets a primer diluted 1:1 with water (roughly 400–600 sq ft per gallon of concentrate), non-porous surfaces like tile or VCT get an undiluted primer at a lower rate (roughly 150–300 sq ft per gallon), and wood subfloors get their own undiluted primer. Very absorbent concrete may need a double-prime — two coats, the first more diluted than the second.
How thick can I pour self-leveling compound?
It depends on the product. Most standard SLUs are rated to about 1–1.5" neat (without aggregate); MAPEI Ultraplan Easy is rated to a full 2". Beyond that, ARDEX K 15 and Henry 555 can be extended with pea-gravel aggregate up to about 5", but neither manufacturer publishes a bag yield for the aggregate-extended mix — so a bag-count calculator (including this one) can't responsibly estimate that range. Follow the product's own technical data sheet for the aggregate mix ratio, and expect to prime and buy extra bags for a thin neat top-coat over the aggregate fill.
What's the minimum floor flatness self-leveling compound needs to achieve?
It depends on your finish flooring. Resilient flooring (vinyl, LVP) generally needs 3/16" in 10 ft per ASTM F710. Tile needs 1/4" in 10 ft under ANSI A108.02 for most tile sizes, tightening to 1/8" in 10 ft for large-format tile with any edge 15" or longer. Wood flooring under NWFA guidelines needs 3/16" in 10 ft for glue-down or short-fastener installs. Self-leveling compound is how you get an out-of-flat subfloor to meet whichever of these targets your finish floor requires.
Can self-leveling compound fix a bouncy or sagging floor?
No — it's a flooring underlayment, not a structural repair. Every major manufacturer caps the subfloor deflection it can be poured over, typically L/360 (L/720 under natural stone), and says explicitly that loose, deflecting, or damaged framing must be corrected first. If your floor bounces noticeably when you walk on it, that's a structural issue — see a framing contractor or the Joist Span Calculator before you pour anything over it.