Calculator

Length (ft)

Width (ft)

Thickness (in)

Cubic Yards

Cubic Feet

80 lb Bags

60 lb Bags

50 lb Bags

Bag counts use standard pre-mixed concrete yields (80 lb ≈ 0.60 ft³, 60 lb ≈ 0.45 ft³, 50 lb ≈ 0.375 ft³) and are rounded up. Add 5–10% extra for spillage and uneven subgrade.

Enter the slab's length, width, and thickness to calculate concrete volume and bag counts.

How to Use the Concrete Calculator

Length and width go in feet, but depth goes in inches — that unit split is intentional, since suppliers quote slab thickness in inches even when everything else is in feet.

Slab volume is just length times width times depth, with one unit trap: depth is almost always quoted in inches while the other two dimensions are in feet.

cubic feet = length (ft) × width (ft) × (depth (in) ÷ 12)

This Concrete Calculator converts that volume into cubic yards (what ready-mix suppliers actually sell) and bag counts for the three common pre-mixed sizes, using published yields — 0.6 ft³ per 80 lb bag, 0.45 for 60 lb, 0.375 for 50 lb. Buy a little more than the raw number suggests; spillage and an uneven subgrade eat 5–10% in practice, which the bag counts here don't pad in for you.