How Much Concrete for 4x4 Post Footings?
Concrete to buy
0.53 cubic yards
Eight round 10 in piers, 3 ft below grade, finished flush with grade, ten percent 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.
- Pier shapeRound, sonotube
- Diameter or side10 in
- Depth below grade3 ft
- Height above grade0 in
- How many piers8 count
- Waste allowance10 %
Concrete to buy0.53 cubic yards
| Height of each pier | 3 ftbelow grade plus what stands above it |
|---|---|
| Section area | 0.545 sq ftround |
| Concrete per pier | 1.64 cu ft |
| Concrete for all piers | 13.1 cu ft |
| With waste | 14.4 cu ft |
| 60 lb bags | 320.45 cu ft each |
| 80 lb bags | 240.60 cu ft each |
| Sonotube at 12 ft | 24 piers cut from one tube |
| Vertical rebar | 66 ft3 bars per pier |
| Bearing at 2,000 psf | 1,091 lbper pier, presumptive soil |
The material list this produces
| Concrete, cu yd | 1 |
|---|---|
| Or 80 lb bags | 24 |
| Sonotube, 12 ft lengths | 2 |
| Rebar, ft | 66 |
| Rebar tie wire, lb | 1 |
| Post bases or anchor bolts | 8 |
How many footings compared
Count swept with the size and the depth held. The two columns are the same concrete counted in 60 lb bags and in 80 lb bags. The line worth finding is the cubic yard: below it a bag job is reasonable, above it a short load from a truck is usually cheaper and always faster.
| How many footings | Concrete to buy | 60 lb bags | 80 lb bags |
|---|---|---|---|
| 4 footings | 0.27 cubic yards | 16 | 12 |
| 6 footings | 0.4 cubic yards | 24 | 18 |
| 8 footings | 0.53 cubic yards | 32 | 24 |
| 12 footings | 0.8 cubic yards | 48 | 36 |
| 16 footings | 1.07 cubic yards | 64 | 48 |
| 24 footings | 1.6 cubic yards | 96 | 72 |
What else matters here
Eight 10 in footings 3 ft down is 1.64 cu ft each and 0.53 cu yd in total, which is 24 eighty pound bags or 32 sixty pound ones. Two sonotubes cover all eight, because each pier is 3 ft tall and four of them come out of a 12 ft tube.
This is the size of job where the bag question is real. Twenty four eighty pound bags is 1,920 lb. That is a full pallet, it is a pickup with the springs flat, and it is most of a day with a mixer if it is only one person doing it. The calculator prints both bag sizes because the 60 lb bag is easier to carry and there are more of them, and which of those matters depends on who is carrying.
The table below sweeps the count, and the useful line in it is a cubic yard. At 16 footings this layout is 1.07 cu yd and 48 eighty pound bags, and at that point a short load from a ready mix truck is usually cheaper than the bags and is certainly faster. At 24 footings it is 1.6 cu yd and 72 bags, which is not a bag job at all. Mixing by hand is a choice worth making deliberately rather than by default.
One 10 in footing carries about 1,091 lb on presumptive 2,000 psf soil. Whether that is enough is the load's question and not the post's, and a 4x4 under a fence rail and a 4x4 under a roof are not the same problem.
What this calculator assumes
- Depth below grade is measured to the bottom of the pier. A footing that stops above the frost line heaves, and the frost depth where you are building is published by your building department.
- Concrete yields are the printed ones: a 60 lb bag makes 0.45 cubic feet and an 80 lb bag makes 0.60.
- Sonotube is nested out of 12 ft lengths rather than divided into them, so a 4.5 ft pier gets two out of a tube and a 6.5 ft pier gets one. The tube line is what you actually buy.
- Bearing is shown at 2,000 pounds per square foot, which is the presumptive value most residential codes allow without a soils report. Soft or filled ground is less and a report can allow more.
- Vertical steel is two bars in a pier under 10 inches, three from 10 to 16, and four above that, each run the full height with three inches of cover at the bottom.
- Anything over about a cubic yard in total is usually cheaper and far faster from a ready mix truck with a short load fee than it is from bags.
Questions people ask
How much concrete for a 4x4 post footing?
A 10 in round footing 3 ft deep is 1.64 cu ft, which is about 3 eighty pound bags. Eight of them is 0.53 cu yd, 24 eighty pound bags or 32 sixty pound.
At what point should I order a truck instead of bags?
Around a cubic yard. Sixteen of these footings is 1.07 cu yd and 48 eighty pound bags, and at that point a short load with a delivery fee is usually cheaper than the bags and much faster to place.
How many sonotubes for eight 4x4 post footings?
Two. Each pier is 3 ft tall and a tube is 12 ft, so four whole piers come out of one tube.
The concrete footing calculator takes any dimensions you like and hands back the same list.