How Much Concrete for a 3x3 Pad?
Concrete needed
0.12 cubic yards
A 3 by 3 foot pad at four inches, with ten percent on top for waste.
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How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Length3 ft
- Width3 ft
- Thickness4 in
- Waste allowance10 %
Concrete needed0.12 cubic yards
| Volume | 3 cu ft |
|---|---|
| Cubic yards before waste | 0.11 |
| Cubic yards with 10% waste | 0.12order to this number |
| Order in quarter yards | 0.25 cu yd |
| 60 lb bags, if bagging it | 8 |
| 80 lb bags, if bagging it | 6 |
The material list this produces
| Ready mix concrete, cubic yards | 0.25 |
|---|---|
| Rebar or mesh, sq ft of slab | 9 |
| Form lumber, linear ft | 12 |
Thickness compared
Thickness is the one number on this page worth arguing about, so here is the same slab at each of the usual four.
| Thickness | Concrete needed |
|---|---|
| 4 in | 0.12 cubic yards |
| 5 in | 0.15 cubic yards |
| 6 in | 0.18 cubic yards |
| 8 in | 0.24 cubic yards |
What else matters here
Three cubic feet. This is a condenser pad, a meter base, a small equipment stand or the bottom of a downspout, and it is unambiguously a bag job: six eighty pound bags mixed in a wheelbarrow in under an hour.
What ruins a pad this small is not the mix, it is what is under it. Four inches of compacted gravel, tamped properly, is the difference between a pad that sits flat for twenty years and one that tips within two winters. Concrete has almost no ability to span a soft spot at this size.
If it is a condenser pad, get it level and keep it level. A heat pump or air conditioner sitting on a tilted pad runs its compressor off level and puts a steady strain on the line set where it enters the cabinet, which is a slow and expensive way to fail.
What this calculator assumes
- One cubic yard is 27 cubic feet. A 4 inch slab is one third of a foot thick, not 4.
- A 60 lb bag yields about 0.45 cubic feet and an 80 lb bag about 0.60. Bags are for small pours only; past about one cubic yard, ready mix is cheaper and far less work.
- Ready mix is usually sold in quarter yard steps with a short load fee below one yard.
Questions people ask
How many bags of concrete for a 3x3 pad?
About 8 sixty pound bags or 6 eighty pound bags at 4 inches thick, including a ten percent waste allowance.
How thick should an AC condenser pad be?
Four inches over four inches of compacted gravel is standard. The gravel base matters more than the thickness on a pad this small.
Do I need rebar in a 3x3 pad?
No. At this size reinforcement does nothing useful. A properly compacted base is what keeps it flat.
The concrete calculator takes any dimensions you like and hands back the same list.