How to measure an uneven floor
Self-leveler has to sit over the whole floor, so the question is not how deep the low spot is, but how far it is below the high point. Lay a long straight level or a string line across the floor in several directions. Mark the highest place you find, then measure the biggest gap to the floor.
Then read the product's minimum. ARDEX K 15 has to go at least 1/8 inch over the highest point, which it says typically results in an average thickness of 1/4 inch, and MAPEI Ultraplan Easy asks for 1/16 inch. Your bags have to cover that high point as well as filling the low one. This is the step most people miss, and it is why estimates built on low spots alone run short.
The calculator assumes an even slope. A floor with a sharp dip in one corner uses less, and a wavy one uses more, so for anything unusual, split the floor into areas and work each out separately. If it moves underfoot, fix that first. Underlayment is not a structural repair.
A worked example
Here is 100 square feet of floor with half an inch from high to low, using LevelQuik RS and 1/8 inch over the high point. These lines come from the same formula the calculator above runs.
100 sq ft, 1/2 in variation, LevelQuik RS
- Average depth: 0.125 + 0.25 = 0.375 in
- Volume: 100 × 0.375 ÷ 12 = 3.13 cu ft
- Bags: 3.13 ÷ 0.479 = 6.52, so 7
- Deepest pour: 0.625 in, within one lift
Sika's printed figures leave out porosity and waste, and no maker gives a percentage for that, so buy a spare bag. A stop in the middle of a pour can leave a cold joint, which is far more costly than a bag you return. Afterward, see the flooring calculator or the tile calculator for what goes on top.
Bags of self-leveler by average depth
These use the middle product, LevelQuik RS, at its low-end coverage. Other products sit close by: SikaLevel lists 21 square feet at 1/4 inch and Ultraplan Easy lists 24, where LevelQuik lists 23 to 24.
| Average depth | A bag covers | 100 sq ft | 200 sq ft | 500 sq ft |
|---|---|---|---|---|
| 1/8 in | 46.0 sq ft | 3 | 5 | 11 |
| 1/4 in | 23.0 sq ft | 5 | 9 | 22 |
| 3/8 in | 15.3 sq ft | 7 | 14 | 33 |
| 1/2 in | 11.5 sq ft | 9 | 18 | 44 |
| 3/4 in | 7.7 sq ft | 14 | 27 | 66 |
| 1 in | 5.8 sq ft | 18 | 35 | 87 |
Mistakes that ruin a pour
- Measuring only the low spots. The product has to cover the high point too, and that adds across the whole floor.
- Pouring past one lift. Custom stops at 1.5 inches, and Sika and MAPEI at 2. Go deeper in stages, or with what the data sheet allows.
- Mixing partial bags. Working time is short, with Sika's pot life at about 25 minutes. Mix whole bags to the printed water ratio.
- Skipping the primer. Most data sheets require it. Without it, a thirsty floor can pull water out of the mix.
- Treating it as a fix for a bad floor. It will not stop a subfloor from moving, and it is not a moisture barrier.
Questions
How many bags of self-leveler do I need?
For 100 square feet with half an inch of variation, about 7 bags of LevelQuik RS, since the average depth works out at 3/8 inch. At a thin 1/4 inch average a 50 pound bag covers about 21 to 24 square feet.
How much self-leveling concrete for 100 square feet?
About 5 bags at a quarter inch average, using a yield of 21 to 24 square feet per 50 pound bag at that depth, and about 9 at half an inch. Floors are rarely even, so measure yours and buy a spare bag.
How thick can self-leveling compound be poured?
Up to 1.5 inches in a lift for LevelQuik RS, and up to 2 inches for SikaLevel and Ultraplan Easy. Sika allows up to 2.5 inches with pea gravel. Read the data sheet for yours, and pour in lifts if you need to go deeper.
How do I measure low spots?
Lay a long straight level or pull a string line across the floor, find the highest point, then measure the gap at the lowest point. The product also has to cover the high point, by 1/16 to 1/8 inch depending on the product, so measure from there.
Do I need to prime before pouring?
Usually yes, since most data sheets require a primer, especially on wood or porous concrete. Follow your product's own rule. Primer keeps the floor from pulling water out of the mix and stops it from curing properly.
Why do I have to cover the high point?
A self-leveler needs a minimum thickness everywhere to bond and to flow flat. ARDEX says 1/8 inch over the highest point typically results in an average of 1/4 inch over the floor. A measurement of only the low spots will leave you short.
This self-leveler count is a planning estimate that assumes an even slope across the floor, which real floors rarely have. Coverage shifts with substrate, equipment and how you pour, and printed coverage leaves out waste. Follow the label on priming and lift depth, and ask your supplier. This will not fix a subfloor that moves, or stop moisture.
Sources and review
- SikaLevel product data sheet, Sika USA, 2026.
- LevelQuik RS technical data sheet, Custom Building Products, 2026.
- Ultraplan Easy technical data sheet, MAPEI, 2024.
- ARDEX K 15 specification, ARDEX, 2011.
Checked in November 2026. Spotted a wrong number? Report it and it goes in the corrections log.
How this is calculated
Every figure below is read from the code that produces the answer, so what is written here is what the calculator ran. The constants were last checked against their sources in November 2026.
The arithmetic
Average depth
Average depth = Cover over the high point + Variation ÷ 2
- Variation
- Inches between the highest and lowest points
- Cover over the high point
- The product's minimum
Worked through: 0.125 + 0.25 = 0.375 in
Bags
Bags = Area × Average depth ÷ 12 ÷ Yield per bag, rounded up
- Yield per bag
- Cubic feet from one bag
Worked through: 4.375 ÷ 0.4375 = 10 bags
The constants, and where they come from
YIELD_CU_FT
Published figureCubic feet from one 50 lb bag, by product
- levelquik
- 0.4791666666666667
- sikalevel
- 0.4375
- ultraplan
- 0.5
Applies to: These three products. Other bags differ, such as ARDEX K 15 at 55 lb
Source: SikaLevel product data sheet, Sika USA, published 2026-05, read 2026-11.
Also from: LevelQuik RS technical data sheet, Custom Building Products, published 2026, read 2026-11.
Also from: Ultraplan Easy technical data sheet, MAPEI, published 2024-06, read 2026-11.
Worked from printed coverage at 1/4 inch. Sika says its figures include no allowance for surface profile, porosity or waste, which is why a waste field is offered. Mapei's 3/4 inch row is out of line with its others and was not used.
MAX_LIFT_INCHES
Published figureDeepest single lift, by product, in inches
- levelquik
- 1.5
- sikalevel
- 2
- ultraplan
- 2
Applies to: As printed on each data sheet. Sika allows up to 2.5 inches with pea gravel
Source: LevelQuik RS technical data sheet, Custom Building Products, published 2026, read 2026-11.
Also from: SikaLevel product data sheet, Sika USA, published 2026-05, read 2026-11.
Also from: Ultraplan Easy technical data sheet, MAPEI, published 2024-06, read 2026-11.
Custom says up to 1.5 inches, and Sika and Mapei up to 2 inches in a single application.
INCHES_PER_FOOT
DefinitionalInches in one foot
Applies to: Definitional, everywhere
True by definition, so there is nothing to cite. The derivation is below.
Twelve inches make a foot by definition, so a depth in inches is divided by 12 to find the volume.
What the labels mean
- Published figure:
- taken directly from the source named beside it.
- Definitional:
- true by definition, like the number of inches in a foot, so there is nothing to cite.
If a figure here looks wrong, it may be. Tell us what you found and we will check it against the source and publish a correction if it needs one. How constants are chosen and how often they are reviewed is set out in our methodology.
How to use the self-leveling concrete calculator
- 1
Measure the floor area
- 2
Find the high point with a long level, and measure down to the lowest point
- 3
Choose the product, and enter its minimum over the high point
- 4
Read the bags and the deepest pour
- 5
Buy a spare, because a stop in the middle of a pour leaves a cold joint
What this calculator assumes
Every estimate here rests on the assumptions below. Where your job differs from one of them, the figure will differ too.
- The floor slopes evenly between the high and low points, so the average depth is half way, plus the cover over the high point
- Bag yields come from each maker's printed coverage at 1/4 inch
- It adds nothing for waste or surface porosity unless you set a figure, and no source gives one
- The product is primed and poured as its data sheet says. It is not a structural repair
Pro tips
- Have every bag, the water and a helper ready before you start, since working time is short
- Dam off doorways and fill any cracks where the mix could escape
- Check the mix ratio on the bag, because too much water weakens it