How to calculate it yourself
Bags = (floor area in ft² × average depth in inches) ÷ 6.25. Each 50 lb bag yields ~0.5 ft³ when mixed = 6.25 ft² at 1 inch deep. Always order 10-15% extra — SLC is unforgiving once the bucket is mixing and a short bag halfway through ruins the pour.
Common scenarios
Kitchen floor, ⅛-in skim (200 ft²)
Skim coat over plywood subfloor before tile install: 8 bags of 50 lb basic SLC ($40-60/bag = $320-480). Mix with a heavy-duty drill paddle in 5-gal pails. Pour in zones, working from far wall toward exit. Total job: half a day, ready to tile in 4-24 hours.
Basement leveling (800 ft², ¼-in average)
60 bags of 50 lb SLC ($40-65/bag = $2,400-3,900). At this volume, 2 people minimum (one mixing, one pouring continuously). Most contractors use a continuous mixer/pump at this size — DIY is achievable but exhausting.
Repair patch under appliance (10 ft² × ¾ in deep)
Just 2 bags ($80-130). Use fast-setting SLC with a primer coat. Walkable in 4 hours, ready for the appliance in 24.