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Concrete Calculator (Slabs, Footings, Columns)
Calculate cubic yards, cubic meters, and 60 lb / 80 lb bag counts for slabs, footings, and columns. Includes 10% waste factor by default.
Shape
ft
ft
in
%
10% slab · 15% footing
Pour estimate
Cubic yards
5.43
Cubic feet
146.7
Cubic meters
4.15
80 lb bags
245
Includes 10% waste · under ½ yd³ buy bags · over 1 yd³ order ready-mix.
How this is calculated
The math
Volume = length × width × depth, with a 10% waste factor on top.
- 1 cubic yard = 27 cubic feet ≈ 0.765 cubic meters
- 60 lb bag yields ≈ 0.45 ft³ (Quikrete & Sakrete spec)
- 80 lb bag yields ≈ 0.60 ft³
Bags vs. ready-mix?
- Under ½ yd³ → bags. ~50 bags = a yard, but it's manageable.
- Over 1 yd³ → call for ready-mix delivery (per-yard pricing).
- Always order 10% extra. Concrete trucks deliver in fixed yards, and a partial second pour is a disaster.
Footings vs. slabs
Footings carry load — use 15% waste, not 10%, because they often run wide of plan.
Frequently asked
- Yes — add 10% for slabs and 15% for footings. Concrete trucks deliver in fixed yards, and over-pouring is much cheaper than running short.
- Under ~0.5 yd³ → bags. Over ~1 yd³ → ready-mix. Between → run the math both ways above.