Concrete Bag Count Calculator
Calculate how many bags of concrete mix you need for any project.
Supports 40, 60, and 80 pound bags.
Concrete bag calculations are essential for DIY projects like fence posts, small slabs, steps, and repairs. Pre-mixed bags are sold in 40 lb (18 kg), 60 lb (27 kg), and 80 lb (36 kg) sizes.
Yield per bag:
- 40 lb bag — 0.011 cubic yards / 0.30 cubic feet / 8.5 liters
- 60 lb bag — 0.017 cubic yards / 0.45 cubic feet / 12.7 liters
- 80 lb bag — 0.022 cubic yards / 0.60 cubic feet / 17.0 liters
The formula: Volume needed (cubic feet) = Length (ft) × Width (ft) × Depth (ft) Bags needed = Volume (cubic feet) / Yield per bag (cubic feet)
Common project volumes:
- Fence post hole (10 in diameter × 24 in deep): 1.1 cu ft → 2 bags of 60 lb
- Sidewalk section (3 ft × 4 ft × 4 in): 4 cu ft → 7 bags of 60 lb
- Small pad (4 ft × 4 ft × 4 in): 5.3 cu ft → 9 bags of 60 lb
- Steps (3 ft wide × 3 steps): varies, typically 10–20 bags
Bag size recommendations:
- 40 lb bags: Best for small repairs and when you need to carry bags by hand to difficult locations
- 60 lb bags: Best all-around choice for medium projects (good balance of weight and yield)
- 80 lb bags: Most economical per cubic foot, best for larger projects near vehicle access
Mixing tips: One 60 lb bag needs approximately 0.5 gallons (1.9 liters) of water. Mix in a wheelbarrow or mixing tub. The consistency should be like thick oatmeal — not runny, not crumbly. Add water gradually. You can always add more water but cannot remove it.
Tip: Always buy 10% extra bags. Spillage, overfilling forms, and slight measurement errors mean you will typically use a bit more than calculated. Unused bags store well in a dry location for months.