Tool · C-01
Concrete bag calculator
Slabs, footings, post holes. Tell it your dimensions, pick your bag size — get an exact count with waste factor included.
Shape
Length
ft
Width
ft
Thickness
in
Bag size
Waste factor10%
Default 10%. Bump to 15% for irregular pours or first-timers.
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Reference · Bag yields
Pocket conversion table
40 lb bag
0.3 ft³
≈ 3.33 bags / ft³
60 lb bag
0.45 ft³
≈ 2.22 bags / ft³
80 lb bag
0.6 ft³
≈ 1.67 bags / ft³
Setting fence posts? You need a different bag math.
For post holes, the displacement of the post itself changes the count. Read the field guide for 4×4, 6×6, and round-post bag math.
Full guide: How many bags of concrete for a fence post? →AdvertisementAd slot 3 · near footer · responsive · responsive