How to use the self-leveling concrete calculator
- Enter the length and width of the area to be leveled.
- Enter the thickness in inches. Coverage comes from Sakrete’s 50 lb bag midpoints: 55 sq ft at 1/8 in, 27.5 at 1/4 in, 13.5 at 1/2 in, interpolated between them.
- Enter a waste allowance. The default 10% is a CalcTheJob planning starting point. The bag count rounds up.
A structural slab or pad stays on the concrete calculator and the concrete slab cost calculator.
Sakrete coverage midpoints
Sakrete’s Self-Leveling Underlayment data sheet lists 50–60 sq ft per 50 lb bag at 1/8 in, 25–30 at 1/4 in, and 12–15 at 1/2 in. This page uses those midpoints at the three published thicknesses. Between them it works from yield (coverage × thickness): 6.875 sq ft·in per bag at 1/8 and 1/4 in and 6.75 at 1/2 in (a pure inverse of 55 would give 13.75 sq ft at 1/2 in; the published 13.5 is used). Yield is interpolated between 1/4 and 1/2 in, so 3/8 in gets about 18.2 sq ft per bag. Below 1/8 in or above 1/2 in the page extrapolates and says so. Bags = area × (1 + waste) ÷ coverage, rounded up.
A worked example: 12×10 ft at 1/4 inch
A 12 × 10 ft room is 120 sq ft. At 1/4 inch the midpoint coverage is 27.5 sq ft per 50 lb bag. With 10% waste you need 120 × 1.10 ÷ 27.5 = 4.8 bags, so 5 bags.
Sources & assumptions
How this calculator gets its numbers. Full method: our methodology.
- Bag yield follows Sakrete’s 50 lb Self-Leveling Underlayment coverage bands: 50–60 sq ft at 1/8 in, 25–30 at 1/4 in, 12–15 at 1/2 in. This page uses the midpoints (55 / 27.5 / 13.5 sq ft) at those thicknesses; between them coverage = interpolated yield ÷ thickness (yield 6.875 sq ft·in per bag at 1/8–1/4 in, 6.75 at 1/2 in). The 1/2 in midpoint of 13.5 is slightly below a pure inverse (13.75). Thicknesses outside 1/8–1/2 in are extrapolated and flagged.
- Default 10% waste is a CalcTheJob planning starting point. Bag count rounds up.
- This is a thin underlayment takeoff, not a structural slab pour.
Sources
- Sakrete, Self-Leveling Underlayment product data sheet (50 lb). Published coverage: 50–60 sq ft at 1/8 in, 25–30 at 1/4 in, 12–15 at 1/2 in per 50 lb bag.
Last reviewed . The coverage printed on the bag you buy wins.
Frequently asked questions
How many bags of self-leveler for 120 sq ft at 1/4 inch?
Using Sakrete’s midpoint of 27.5 sq ft per 50 lb bag, 120 sq ft plus 10% waste is 4.8 bags, so buy 5.
Where do the coverage numbers come from?
Sakrete’s 50 lb Self-Leveling Underlayment product data sheet: 50–60 sq ft at 1/8 in, 25–30 at 1/4 in, 12–15 at 1/2 in. This page uses the midpoints.
Is this a concrete slab calculator?
No. It is a thin underlayment takeoff. Structural slabs stay on the concrete calculator.
Can I enter a thickness that is not 1/8, 1/4 or 1/2 inch?
Yes. At 1/8, 1/4 and 1/2 inch the published midpoints are used (55, 27.5 and 13.5 sq ft). In between, coverage follows the interpolated yield (3/8 in ≈ 18.2 sq ft per bag). Outside 1/8–1/2 in the result is flagged as an extrapolation beyond the data sheet.