80 lb Concrete Bag Calculator
Work out how much concrete a slab, footing, column pour or a batch of fence post holes needs: pick the shape, enter its real dimensions, and get the volume in cubic yards and cubic meters plus the number of pre-mixed bags to buy.
Result
This page opens the concrete calculator for a slab pour with the 80 lb pre-mixed bag size already selected — the bag most home-improvement stores stock as their standard size, since fewer, bigger bags mean fewer trips for a given volume. Enter the slab's length, width and thickness and the calculator handles the rest.
An 80 lb bag has a published typical yield of about 0.60 ft³ once mixed — noticeably more per bag than a 60 lb bag's 0.45 ft³, so for the same slab you'll carry roughly 25% fewer bags, at roughly 33% more weight each. A 10 × 10 ft slab at 4 inches (33.33 ft³) needs about 56 bags of 80 lb mix versus about 75 bags of 60 lb mix for the identical pour — worth weighing against how much weight you (or your crew) want to lift per trip.
The yield figure is a typical published number, not a guarantee — bag formulas vary slightly by manufacturer and region, so check the exact yield printed on your specific bag before finalizing an order. The waste checkbox adds a 10% margin for spillage and an uneven subgrade before the bag count is calculated. Everything runs locally in your browser.