Self-Leveling Underlayment Bag Count
Self-leveling underlayment (SLU) bags, where the yield depends on the average pour thickness: neat bags = area x thickness / bag yield (square-foot-inches); bags = ceil(neat x (1 + waste)). 500 sf poured at 1/4 in average, on a 6.25 sf-in bag yield, is 20 bags neat - 21 with waste; a deeper 1/2 in average doubles it to 42. The average thickness drives the order, so a low floor with deep spots eats material. SLU sets fast - stage bags first.
Formula and source
neat_bags = area_sf x avg_thickness_in / bag_yield_sf_in; bags = ceil(neat_bags x (1 + waste_pct/100)).
Self-leveler bag-count identity by name (volume of underlayment over the per-bag yield, plus waste); first-principles arithmetic.
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