Bed area (ft²), depth (inches), bag size (ft³)—bags to buy (rounded up).
Given rectangular area (ft²), depth (inches), and bag coverage (ft³ per bag) (all positive), the model computes soil volume area × (depth ÷ 12) in cubic feet, then bags = ⌈volume ÷ bag_size⌉. This is a rough material estimate, not a compaction or spillage model.
This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.