The Field Calculators → Build
Build
Concrete & gravel volume
Slabs, footings and post holes — in bags, so you buy once.
Result
What are you pouring?Slab / rectangular pad
Length (or hole diameter, in)10 ft / in
Width (ignored for holes)10 ft
Thickness / hole depth4 in
How many holes (holes only)1
Waste allowance10 %
Volume
36.7 cu ft
1.36 cubic yards.
80 lb bags
62
An 80 lb bag yields about 0.6 cu ft.
60 lb bags
82
Ready-mix
1.50 yd — worth a truck
Most ready-mix suppliers have a minimum of 1 yard and a short-load fee.
Water needed
46.5 gal
About 3 quarts per 80 lb bag.
What this will not do
- Mixing more than about 10 bags by hand is a bad afternoon. Rent a mixer, or order a truck — concrete does not wait for you to catch up.
- Order 10% extra. Running short mid-pour leaves a cold joint you'll look at for twenty years.
- Post holes: below your local frost line, or the frost will lift the post out over a few winters.