How Many Bags of Concrete for a 6x6 Deck Post?
One 6x6 post in a 12" hole 36" deep needs 4 bags of 60 lb concrete.
4bags
60 lb bags · estimated $23.92 at $5.98/bag
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Estimated cost: ~$23.92 (4 × $5.98/bag, Spring 2026 pricing)
Bag size
Multi-bag comparison
| Bag size | Bags | Price/bag | Total |
|---|---|---|---|
| 80 lbBest value | 3 | $6.98 | $20.94 |
| 60 lb | 4 | $5.98 | $23.92 |
| 40 lb | 6 | $4.98 | $29.88 |
Prices are spring 2026 estimates. Above ~60 bags, price a ready-mix truck too — it is often cheaper.
Material list
- 4 × 60 lb concrete mix bags — $23.92 @ $5.98/bag (Spring 2026)Home Depot ↗Lowe's ↗
- Wheelbarrow or mixing tub
- Mixing hoe or drill paddle
- Margin trowel or float
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4 bags(60 lb)
$23.92
How this is calculated
We convert your dimensions to cubic feet, add a 10% waste buffer for spillage and an uneven subgrade, then divide by the bag's yield and round up to the next full bag.
FAQ
How many bags of concrete per 6x6 deck post?
One 6x6 deck post set in a 12-inch hole 36 inches deep needs about 4 bags of 60 lb or 3 bags of 80 lb concrete, with waste included.
How much concrete do I need for 5 6x6 deck posts?
About 20 bags of 60 lb concrete for 5 posts. Buy one or two extra bags so you do not run short mid-set.
Can I use fast-setting concrete for a 6x6 deck post?
Yes. Many people pour fast-setting mix straight into the hole and add water. The number of bags is the same as standard mix.