Concrete Mix Calculator
Calculate cement bags, sand, gravel, and water needed for any concrete pour. Supports slabs, columns, footings, and tube fills. Includes premix bag estimates and ready-mix thresholds.
Concrete mix strength
Pour shape
Length
ft
Width
ft
Thickness
in
Waste factor
%
5–10% typical, 15%+ for complex pours
Volume (cubic yards)
1.36 CY
incl. 10% waste
Volume (cubic feet)
36.67 CF
1.038 m³
Ready-mix?
Consider ordering
Ready-mix typically cheaper >0.5 CY
Materials needed (scratch mix)
Portland cement
8 bags
94 lb / bag
Sand
0.48 CY
≈1300 lbs
Gravel / aggregate
0.96 CY
≈2697 lbs
Water
42 gal
w/c ratio 0.5
Premix bag alternative
40 lb bags
2420 bags
Easiest to handle
60 lb bags
1650 bags
Most common
80 lb bags
1247 bags
Fewer trips
Mix ratio — 1:1.5:3 (cement:sand:gravel)
CementSandGravel
Mixing and placement tips
For scratch mixes, always add water gradually — too much water weakens concrete significantly. The water-to-cement ratio (w/c) is the most important factor: lower is stronger. For pours over 0.5 cubic yards, ready-mix concrete is typically more economical and ensures consistent quality. Always order 10% extra to account for spillage and irregular surfaces. Cure concrete slowly — keep it moist for at least 7 days for best strength.
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