4×8 shed pad
A 4×8 ft shed pad at 4 in is just under 0.4 cubic yards — about 22 of the 80 lb bags. Small enough to mix on site with a wheelbarrow or a portable mixer.
Inputs
4 in is standard for slabs
Extra for spillage and subgrade
How it's calculated
cubic feet = length × width × (thickness ÷ 12)
One 80 lb bag yields about 0.6 cubic feet; a 60 lb bag about 0.45. Past roughly 1 cubic yard (56 bags of 80 lb), ready-mix delivery is cheaper and faster.
Under-ordering on bag mix. Bags are rated by dry weight, not finished volume — always divide your cubic feet by the yield, then round up every bag.
Cost to Build a Fence
Frequently asked
- How many 80 lb bags of concrete make a cubic yard?
- About 45 bags. Each 80 lb bag yields roughly 0.6 cubic feet, and a cubic yard is 27 cubic feet, so 27 ÷ 0.6 ≈ 45 bags.
- How thick should a concrete slab be?
- 4 inches is standard for patios, sheds, and walkways. Driveways and garage floors that carry vehicles are usually poured 5 to 6 inches thick.
- When should I use ready-mix instead of bags?
- Once a pour passes about 1 cubic yard, bagging becomes slow and expensive. Ready-mix delivery is cheaper per yard and gives a single continuous pour.
- Do I need to add for waste?
- Yes. A 10% waste factor covers spillage, uneven subgrade, and over-excavation. Increase it for hand-dug footings or rough ground.
Related tools
Gravel Calculator
Calculate how much gravel you need in cubic yards and tons. Enter length, width, and depth — includes a waste factor for driveways and pads.
Mulch Calculator
Calculate how much mulch you need in cubic yards and 2 cu ft bags. Enter bed length, width, and depth — includes a waste factor.