Self-Leveling Underlayment Calculator
Work out how many bags of self-leveling underlayment to buy for a floor or a single low spot from its area and average pour depth.
Area and pour depth
Type inches as decimals: 0.125 = 1/8 in, 0.1875 = 3/16 in, 0.25 = 1/4 in, 0.375 = 3/8 in, 0.5 = 1/2 in. Use the average depth from a level line at the finished height down to the floor, not the deepest spot.
Results
For 120 sq ft poured to an average depth of 1/4 in, you'll need about 6 50 lb bags of CUSTOM TechLevel 150.
Self-leveling underlayment needed
6 bags (50 lb)
That's a typical amount for leveling a kitchen, bathroom or bedroom floor.
Line up water, buckets and a helper before the first bag: the CUSTOM sheets say to keep a wet edge when pouring multiple mixes, and the SikaLevel sheet lists a pot life of about 25 minutes.
Area: 120 sq ft
Average pour depth: 1/4 in
Coverage per bag at this depth: 22.8 sq ft
Underlayment volume incl. 10% buffer: 2.75 cu ft
CUSTOM TechPrime A Acrylic Primer (one coat): 1 gal (3.8 L) — about 0.2 gal of primer for one coat, before any water is added
How this works
To find how much self-leveling compound you need, multiply the area by the average pour depth, add a 10% BuildyWork planning buffer, divide by the volume one bag fills, and round up to whole bags. A 50 lb bag covers about 45.6 sq ft at 1/8 in deep with CUSTOM TechLevel 150, or 42 sq ft with SikaLevel, and half that at 1/4 in (22.8 and 21 sq ft). Find the area first with the square footage calculator if the room is not a simple rectangle.
| Product | 1/8 in | 1/4 in | 1/2 in | 1 in | Single pour (data sheet) |
|---|---|---|---|---|---|
| CUSTOM TechLevel 150, 50 lb bag | 45.6 | 22.8 | 11.4 | 5.7 | featheredge to 1-1/2 in |
| SikaLevel, 50 lb bag | 42 | 21 | 10.5 | 5.3 | 1/8 in to 2 in |
| CUSTOM LevelLite, 30 lb bag | 45 | 22.5 | 11.2 | 5.6 | featheredge to 2 in |
Self-leveling underlayment fills a fixed volume per bag, so its coverage halves every time the depth doubles. Each sheet prints coverage at a few depths. The calculator works out the volume each row implies (coverage × depth) and uses the smallest, so its coverage at any depth is never more than the sheet's own figure. Where the sheet gives a range, as TechLevel 150 does, it starts from the lower number. For a sloped low spot, the depth is taken to ramp evenly from the shallow edge to the deepest point, so the average depth is halfway between them. Coverage charts and pour-depth ranges come from the CUSTOM TechLevel 150 data sheet (TDS-248), the SikaLevel product data sheet (May 2026), and the CUSTOM LevelLite data sheet (TDS-107), checked 2026-10-30. The sheets print these 1/8 in lines: 1/8" (3.18 mm): 46 - 48 ft² (4.2 - 4.4 M²) per 50 lb bag; 1/8" (3.2mm): 42 ft² per 50 lb. (22.7 kg) bag; 1/8" (3.17 mm): 45 sq. ft. (4.1 M²) per 30 lb bag. The 10% buffer is a BuildyWork planning default with no external source claimed.
Primer amounts use the lower coverage figure the primer maker publishes: CUSTOM TechPrime A Acrylic Primer, Per gallon before dilution: non-porous, undiluted 400-600 ft²; porous, 1:3 (primer:water) 600-1200 ft²; CUSTOM LevelQuik Primer, 1 Gallon (3.78 L) Porous 1:3 (primer:water): 600-1200 ft². No coverage was verified for Sika Level Primer, so the calculator shows no primer amount for SikaLevel.
This page covers pourable self-leveling underlayment, used to flatten a floor before vinyl plank, tile or carpet. A packed sand-and-cement mortar bed or a sloped shower pan is a different product: use the floor mud calculator for those.
Worked example: leveling a kitchen before vinyl plank
A 12 ft × 10 ft kitchen (120 sq ft) needs an average of 1/4 in of underlayment before luxury vinyl plank goes down. TechLevel 150 covers 22.8 sq ft per 50 lb bag at 1/4 in in this calculator, so the floor needs 120 ÷ 22.8 ≈ 5.26 bags, and the 10% BuildyWork buffer brings that to 5.79, rounded up to 6 bags. With SikaLevel at 21 sq ft per bag, it is 132 ÷ 21 ≈ 6.29, so 7 bags. TechPrime A on porous concrete covers at least 600 sq ft per gallon diluted 1:3, so one coat needs about 0.2 gal, which is 1 gallon bottle.
A second example: filling one low spot
A 6 ft × 4 ft low spot (24 sq ft) feathers from nothing at one edge to 3/4 in deep at the other. Its average depth is half of 3/4 in, or 3/8 in. TechLevel 150 covers 15.2 sq ft per bag at 3/8 in, so the spot needs 24 × 1.1 ÷ 15.2 ≈ 1.74, rounded up to 2 bags. Using the 3/4 in deepest reading for the whole spot would have given 3.47, or 4 bags. SikaLevel would get a warning here, because its sheet's minimum layer is 1/8 in and the feathered edge goes thinner.
Common mistakes
Using the deepest spot as the depth for the whole floor
One low spot does not set the depth of the whole pour. Set a level line at the finished height, measure down at several evenly spaced points, and average them, or fill the low spot on its own with the sloped low spot setting.
Leveling the whole room when only one area is low
If most of the floor is already flat, a pour over the whole room at a minimum thickness can cost more than filling just the dip. Run the calculator for the low spot's area, and add a skim of the whole floor only if your flooring needs it.
Skipping the primer
Every sheet here calls for priming the floor first. The LevelQuik Primer sheet says primer improves the adhesion of the underlayment and seals porous surfaces.
Mixing more than you can pour in time
Pot life is short: more than 30 minutes for LevelLite, more than 15 minutes for TechLevel 150, and about 25 minutes for SikaLevel. Mix one bag at a time and keep a wet edge, as the CUSTOM sheets say.
Using a self-leveler where the floor must slope
A self-leveler runs flat. The CUSTOM sheets say not to use their underlayments on sloped surfaces that require drainage, and the SikaLevel sheet says it is not suitable for slopes over 0.5%. Build a sloped shower floor with floor mud instead.
When this calculator's model stops applying
- A bowl-shaped dip, deepest in the middle: the sloped low spot setting assumes the depth ramps evenly from one edge to the other, so its average is halfway. A dip shaped like a shallow cone averages about a third of its deepest point, so the estimate runs high, which is the safe side.
- Several separate low spots: run the calculator for each one and add the bags.
- Pours deeper than the product's single-pour maximum: the calculator still counts bags of neat product and shows a warning. Pour in lifts as the sheet describes. A mix extended with sand or pea gravel, which SikaLevel allows, yields more per bag than this estimate assumes.
- Non-rectangular rooms: use the total area setting, or split the room into rectangles and add their areas.
- Gypsum underlayment, old adhesive or tile underneath: each sheet has its own preparation steps for these, and SikaLevel rules out gypsum-based floors. The bag count is the same, but check the sheet first.
- Coverage on a rough or very porous slab: the SikaLevel sheet says its figures include no allowance for surface profile, porosity or waste. That is what the 10% BuildyWork buffer is for; a very rough slab may need more.
FAQ
Why does the calculator use 45.6 sq ft per bag for TechLevel 150 when the sheet says 46 to 48?
Because it takes the most cautious figure the sheet gives. A bag fills a fixed volume, so coverage times depth should be the same on every row of the chart. On the TechLevel 150 chart, the 1-1/2 in row (3.8 sq ft) works out to slightly less volume than the 1/8 in row (46 sq ft). The calculator uses that smaller volume for every depth, which gives 45.6 sq ft at 1/8 in and never more than any row of the chart.
Do I have to prime the floor first?
Yes, for all three products here. The TechLevel 150 sheet says to prime all surfaces with a CustomTech primer such as TechPrime A, the LevelLite sheet says to prime all surfaces with a CUSTOM primer such as LevelQuik Primer, and the SikaLevel sheet says to always prime concrete and cementitious substrates with Sika Level Primer. The LevelQuik Primer sheet adds that a highly porous slab may need a second coat of diluted primer, which doubles the primer amount shown.
Can I pour self-leveler over a plywood subfloor?
The two CUSTOM sheets list exterior-grade plywood and OSB as suitable substrates, with conditions: the subfloor must be sound and not deflecting, all wood subfloors must be primed, and 2.5 lb/yd² metal lath is fastened every 6 to 8 in over the primed surface. The SikaLevel sheet is written for concrete and cementitious substrates and rules out chipboard, particle board, hardboard, metal and gypsum-based floors. The bag count does not change, but the product choice does.
How deep can I pour in one go, and what if I need more?
TechLevel 150 goes from featheredge to 1-1/2 in in a single pour, LevelLite from feather edge to 2 in, and SikaLevel from 1/8 in to 2 in in localized areas, or up to 2-1/2 in extended with pre-washed 3/8 in pea gravel. For a second layer, the CUSTOM sheets say to pour it once the first has set to a walkable hardness and to re-prime if the first layer has dried over 12 hours. The SikaLevel sheet says to prime the first layer and that the second layer must not be thicker than the first.
How much water goes into each bag?
Follow the sheet for your product. LevelLite takes 5.5 to 6.5 quarts per 30 lb bag, TechLevel 150 takes 5.25 to 5.75 quarts per 50 lb bag, and SikaLevel takes 1 gallon per 50 lb bag, which its sheet says not to exceed. The coverage figures this calculator uses are for product mixed that way.
How soon can I lay flooring over it?
It depends on the product and the flooring. LevelLite and TechLevel 150 list more than 4 hours before ceramic tile or other non-moisture-sensitive coverings and more than 16 hours before moisture-sensitive ones. SikaLevel lists 2 to 3 hours for tile and stone, 1 day for PVC, carpet, vinyl and rubber, and 3 days for hardwood and engineered wood. Check the flooring maker's moisture limits as well.
Why does a 30 lb bag of LevelLite cover almost as much as a 50 lb bag?
LevelLite is a lightweight formula: its sheet says it is 40% lighter than other self-leveling underlayments and that a 30 lb bag covers the same area as a 50 lb bag. Its chart gives 45 sq ft at 1/8 in per 30 lb bag. Compare products by coverage per bag, not by bag weight.
Can I leave self-leveling underlayment as the finished floor?
Not these products. The CUSTOM sheets say not to use LevelLite or TechLevel 150 as a permanent wear surface, and the SikaLevel sheet says it is not intended to be used as a wear layer. All three are for interior use and are meant to be covered by tile, vinyl, carpet, wood or a coating.