How Much Concrete for a 22-Inch Round Footing 36 Inches Deep?
Estimate for a 22" diameter × 36" deep Sonotube footing: cubic feet, cubic yards, and bag counts
Exact and planning quantities for a 22" round footing 36" deep: 7.9194 cu ft (0.2933 yd³), exact bag counts, and waste-adjusted totals for ordering materials.
This is a narrow, tube-form round pour sized 22" diameter × 36" deep. It’s a small-volume footing formed with a Sonotube or similar round form and is easy to quantify for one post or a run of isolated supports.
At 36" deep you’ll dig or set the tube that deep and plan for about 7.9194 cubic feet of concrete per footing. That volume is small enough that bagged concrete is often the simplest way to handle a single footing, but you’ll want to plan waste and reinforcement based on load, soil, and frost depth.
Quick Answer
Exact volume: 7.9194 cubic feet (0.2933 cubic yards) for one 22" diameter × 36" deep round footing.
Planning with 10% waste: 8.7113 cubic feet (0.3226 cubic yards). Exact bag counts are 27 40-lb bags, 18 60-lb bags, or 14 80-lb bags; planning bag counts with waste are 30 40-lb, 20 60-lb, or 15 80-lb.
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How to Use This Footing Estimate
Quick steps to estimate and order for this 22" round, 36" deep footing.
- Confirm the form diameter and depth are 22" and 36" before calculating.
- Use the computed volume (7.9194 cu ft) as the base figure.
- Add the waste allowance (10%) to get 8.7113 cu ft for ordering.
- Decide between bagged concrete or ready-mix based on how many footings you have.
- Round up bag counts to whole bags and keep extra for small overpour or variations.
- If ordering multiple footings, multiply the chosen planning totals by the number of footings.
Formula
Use this round footing formula:
Volume (ft³) = π × Radius (ft) × Radius (ft) × Depth (ft)
3.1416 × 0.92 × 0.92 × 3 = 7.92 ft³
7.92 ÷ 27 = 0.29 yd³
If you add a 10% waste allowance, you should plan closer to 0.32 cubic yards.
Worked Example
Single-footing example: before waste the footing is 7.9194 cu ft (0.2933 yd³). With a 10% waste allowance it becomes 8.7113 cu ft (0.3226 yd³). Exact bags are 27 40-lb, 18 60-lb, or 14 80-lb; planning bags are 30, 20, or 15 respectively.
Multiple-footing example (4 footings): before waste total is 31.6776 cu ft (1.1732 yd³). With 10% waste total is 34.8452 cu ft (1.2904 yd³). Bag totals before waste are 108 40-lb, 72 60-lb, 56 80-lb; planning totals with waste are 120 40-lb, 80 60-lb, 60 80-lb.
Bag Count Estimate
- 15 bags of 80 lb concrete mix
- 20 bags of 60 lb concrete mix
- 30 bags of 40 lb concrete mix
Always verify the actual yield on the product label before buying materials.
Bag Counts by Waste Buffer for 22" diameter × 36" deep
Pick a buffer based on site conditions: clean forms and accurate measurements can run leaner; rough subgrade or hard-to-reach pours need more cushion.
| Buffer | Volume (ft³) | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|
| No buffer | 7.92 | 14 | 18 | 27 |
| +5% typical DIY | 8.32 | 14 | 19 | 28 |
| +10% recommended | 8.71 | 15 | 20 | 30 |
| +15% rough conditions | 9.11 | 16 | 21 | 31 |
When Bagged Concrete vs Ready-Mix Makes Sense
For one 22" × 36" footing, bagged concrete is simpler: you can mix a few dozen bags on site and avoid a minimum ready-mix truck charge. The planning counts above (30 40-lb, 20 60-lb, or 15 80-lb) reflect the waste allowance for a single pour.
If you’re pouring several footings—four or more—the math changes. Total volume and handling time increase and a small ready-mix load may become more efficient. Compare the total yards needed to typical supplier minimums to decide.
Common Uses for This Footing Size
This 22" diameter by 36" deep footing is often used for isolated post supports such as pergola posts, deck posts, small sign supports, or narrow-column footing layouts where a round form is preferred. The footprint is fairly narrow, so it suits layouts where space is constrained or columns are spaced in a linear pattern.
Whether this size will work in a specific location depends on load, soil bearing capacity, frost depth, and reinforcement. Those factors influence required diameter, depth, and steel; plan conservatively and adjust the footing dimensions if loads or poor soils demand it.
Common Mistakes to Avoid
Common estimating and ordering mistakes to avoid for this footing size.
- Not confirming the actual inside diameter of the tube before calculating volume.
- Forgetting the 10% waste allowance and under-ordering material.
- Mixing bag sizes in your head and then miscounting total bags at the site.
- Rounding down yardage or bag counts instead of rounding up.
- Ordering ready-mix without checking supplier minimums relative to the pour size.
- Ignoring the need for reinforcement or rebar placements when that affects concrete volume slightly.
Frequently Asked Questions
What is the exact concrete volume for a single 22" × 36" round footing?
The exact volume is 7.9194 cubic feet, which is 0.2933 cubic yards.
How many bags of concrete do I need?
Exact counts are 27 40-lb bags, 18 60-lb bags, or 14 80-lb bags for one footing. With 10% waste plan on 30 40-lb, 20 60-lb, or 15 80-lb.
Why is a 10% waste allowance used and can I change it?
Ten percent covers overfill, slight depth or diameter variation, and carryover loss. If your measurements are exact and you’re careful, you might reduce waste slightly, but 10% is a safe planning margin for small round pours.
Will this footing size support a typical deck or pergola post?
A 22" × 36" footing is sometimes used for deck or pergola posts and may work in some cases, but adequacy depends on the specific post load, soil bearing, frost depth, and whether reinforcement is used.
Keep Planning Your Concrete Project
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Disclaimer: This page provides planning estimates only. Actual concrete needs vary with excavation accuracy, site conditions, local code requirements, bag yield, and supplier guidance. Always verify measurements before buying materials, and consult a qualified professional for structural or code-sensitive work.