Self-leveling underlayment is sold by the bag with a coverage figure at a stated thickness. Enter the floor area and the average depth you need; the calculator converts the bag coverage into a volume per bag and tells you how many bags to mix.
Self-leveling formula
Yield per bag (cu ft) = coverage at 1/8 in (sq ft) × 0.125 ÷ 12 Volume needed (cu ft) = area × average thickness (in) ÷ 12 Bags = volume ÷ yield per bag, rounded up
Worked example: 200 sq ft at an average 1/4 in
- Custom Building Products lists LevelQuik RS at 46–48 sq ft per 50 lb bag at 1/8 in; using 47 sq ft:
- Yield per bag: 47 × 0.125 ÷ 12 = 0.49 cu ft.
- Volume: 200 × 0.25 ÷ 12 = 4.17 cu ft.
- Bags: 9.
Bags per 100 sq ft
| Average thickness | Bags (47 sq ft at 1/8 in) |
|---|---|
| 1/8 in | 3 |
| 1/4 in | 5 |
| 3/8 in | 7 |
| 1/2 in | 9 |
| 3/4 in | 13 |
| 1 in | 18 |
Finding the average thickness
Self-leveler flows into low spots, so the depth varies across the floor. Lay a long straightedge or laser across the floor in a grid, measure the gap at each point, and average the readings, including the minimum depth the product requires over the high spots. Underestimating is the most common reason people run out mid-pour, so round up.
Questions
How much does a bag of self-leveler cover?
About 46–48 sq ft at 1/8 in and 23–24 sq ft at 1/4 in for LevelQuik RS; other products vary.
Do I need primer?
Most self-levelers require the manufacturer’s primer on the subfloor; follow the bag instructions.
Can I pour it thicker?
Each product has a maximum thickness per pour; deeper fills may need aggregate added or a different product.
Sources
- LevelQuik RS Rapid Setting Self-Leveling Underlayment, Custom Building Products.
Used for: Coverage of 46–48 sq ft per 50 lb bag at 1/8 in.