Self Leveling Concrete Calculator

1. Enter the length and width of the floor.
2. Enter the average depth in inches. For an uneven floor, average the thin and thick spots.
3. Enter the bag yield from your product, in cubic feet. The default suits a 50 pound rapid-set bag.
4. Read the bags needed, rounded up, with the volume and the coverage one bag gives at your depth.

Here is what each result line means:

A self leveling concrete calculator tells you how many bags of self-leveling underlayment to buy to smooth or raise a floor before tile, vinyl, wood or epoxy. Self-leveler is a cement-based powder you mix with water; it flows out and settles flat.

Because floors are rarely a uniform thickness, the key input is the average depth across the area. The tool turns that into a volume and divides by the yield of one bag. To seal or finish the floor afterwards, see the concrete slab calculator for the slab beneath.

The volume is the area times the average depth, converted to feet. Dividing by the yield of one bag gives the bag count, and a waste allowance covers spillage and the fast set.

1. Multiply length by width for the floor area.
2. Multiply by the average depth in feet (inches divided by 12) to get the volume.
3. Divide the volume by the yield of one bag.
4. Add the waste allowance and round up to whole bags.

The average depth is what makes this honest on an uneven floor: a low spot that is deep in places still averages out across the room, so you buy for the real volume rather than the deepest point.

Suppose you are leveling a 10 by 12 foot room, 120 square feet, at an average depth of 1/2 inch, with a bag that yields 0.49 cubic feet and a 10 percent waste allowance.

Calculation: the volume is 120 times 0.5 divided by 12, which is 5 cubic feet. Divided by 0.49 that is 10.2 bags, and adding 10 percent gives about 11.2, so you round up to 12 bags. At half an inch, one bag covers only about 12 square feet, which is why depth matters so much.

The lesson: depth drives the bag count far more than area, so measure the average depth carefully.

Average Depth

This has the biggest effect. Doubling the average depth doubles the bags, so a floor with deep low spots needs far more than a thin skim coat.

Bag Yield

Yield varies by product and bag weight. A 50 pound rapid-set bag is around 0.49 cubic feet; other products differ, so use the figure on your bag.

How Uneven the Floor Is

A badly dished or sloped floor has a higher average depth than it looks, because the deep areas pull the average up. Measure in several places.

Waste and Set Time

Self-leveler sets fast, so you cannot stop mid-pour to buy more. A 10 percent allowance, and an extra bag on hand, prevents a ruined pour.

Self-leveler is one of several ways to fix a floor, and the right choice depends on how much you are correcting.

If you only have a few shallow low spots, a patch may be cheaper than leveling the whole room. For a flat, even base under new flooring, self-leveler is the usual choice.

Prepping for New Flooring

Work out the bags to flatten a subfloor before tile, vinyl plank or wood.

Leveling a Garage or Basement

Estimate a pour to correct slope or dishing in a slab floor.

Avoiding a Failed Pour

Buy the right number of bags, plus a spare, so a fast-setting pour is not ruined by running short.

1. Using the Deepest Point as the Depth

Buy for the average depth, not the deepest spot, or you will badly over-order. Measure in several places and average.

2. Ignoring the Yield on the Bag

Yields differ between products. Using a generic figure instead of your bag can leave you short or long.

3. Running Short Mid-pour

Self-leveler sets in minutes. Keep a spare bag, because a seam from a late batch shows and weakens the surface.

4. Skipping Primer

Most self-levelers need a primer so they bond and do not flash-dry. Primer is extra, and skipping it causes failures.

5. Going Too Thick in One Pass

Each product has a maximum thickness per pour, often around an inch to an inch and a half. Deeper fills may need lifts or a different product.

The math is exact for the depth and yield you enter, but real floors are uneven and products differ, so treat the result as a planning estimate and buy a little extra.

Multiply the floor area by the average depth in feet to get a volume, then divide by the yield of one bag and add about 10 percent. A 120 square foot floor at a half-inch average, with a 0.49 cubic foot bag, needs about 12 fifty-pound bags.

Measure the thickness you need in several places, including the thinnest and deepest spots. A quick estimate is to add the shallowest and deepest depths and halve them; measuring more points gives a better average.

It depends on the depth. A 50 pound bag yielding about 0.49 cubic feet covers roughly 47 square feet at 1/8 inch, but only about 12 square feet at 1/2 inch, because coverage falls as depth rises. Always check your bag.

Most products pour from about 1/8 inch up to 1 to 1.5 inches in a single pass. Deeper fills may need more than one lift or a different product, so check your product maximum.

Usually yes. Most self-levelers need a primer so they bond to the subfloor and do not dry too fast. Primer is a separate cost, and skipping it is a common cause of failure.

Yes. Self-leveler sets in minutes, so you cannot pause to buy more without leaving a seam. Keep a spare bag beyond the calculated amount, which is why the tool adds a waste allowance.

No. A patch fixes small holes and local low spots and feather-edges thin. Self-leveler flows out to level a whole floor at a more even depth. For a few shallow spots a patch is often cheaper.

The arithmetic is exact for your inputs. The uncertainty is in the real average depth and the product yield, so measure carefully, use your bag yield, and buy a little extra.

No. The calculation runs entirely in your browser and nothing you enter is stored or sent anywhere.

• Custom Building Products LevelQuik RS Self-Leveling Underlayment (50 lb bag covers 46-48 sq ft at 1/8 in; up to 1.5 in thick).
• American Concrete Institute (ACI; cement-based underlayments and floor flatness).
• Portland Cement, American Cement Association (American Cement Association; cementitious materials).