How Much Concrete for a 36-Inch Round Footing 24 Inches Deep?
Estimate for a 36" diameter × 24" deep round tube footing: cu ft, cu yd, and bag counts
Exact and waste-adjusted quantities for a 36" diameter by 24" deep round footing — cubic feet, cubic yards, and bag counts for 40 lb, 60 lb, and 80 lb mixes.
This is a narrow, tube-form footing sized 36" diameter × 24" deep intended for isolated post support or a pergola/deck post location. The pour is small but tall enough that the tube form and rebar placement matter.
Plan to excavate about 24" deep and set a 36" diameter Sonotube or similar round form. The numbers below show the exact material volume and a planning allowance with 10% waste so you can decide between bags of concrete mix or ordering ready-mix.
Quick Answer
Exact volume: 14.1372 cubic feet (0.5236 cubic yards).
Planning with 10% waste: 15.5509 cubic feet (0.576 cubic yards). Exact bag counts: 48 40-lb bags, 32 60-lb bags, 24 80-lb bags. Planning bag counts with waste: 52 40-lb bags, 35 60-lb bags, 26 80-lb bags.
Need a custom estimate? Use the Footing Calculator. Browse footing size pages. All project pages.
How to Use This Footing Estimate
Quick steps to estimate and plan this 36" × 24" round footing pour.
- Measure the footing diameter and depth to confirm 36" diameter and 24" deep.
- Check the exact volume listed: 14.1372 cu ft (0.5236 yd3).
- Add a waste allowance (10%) to get 15.5509 cu ft (0.576 yd3) for ordering.
- Decide material: count bagged concrete or order ready-mix based on total quantity.
- If pouring multiple footings, multiply the planning volume and bag counts before buying.
- Round bag counts up to whole bags and set them aside before starting the pour.
Formula
Use this round footing formula:
Volume (ft³) = π × Radius (ft) × Radius (ft) × Depth (ft)
3.1416 × 1.5 × 1.5 × 2 = 14.14 ft³
14.14 ÷ 27 = 0.52 yd³
If you add a 10% waste allowance, you should plan closer to 0.58 cubic yards.
Worked Example
Single footing example: before waste the footing needs 14.1372 cu ft (0.5236 yd3). With a 10% allowance plan on 15.5509 cu ft (0.576 yd3). Exact bag counts are 48 40-lb, 32 60-lb, 24 80-lb; planning counts are 52 40-lb, 35 60-lb, 26 80-lb.
Multiple-footing example (4 footings): total before waste = 56.5488 cu ft, 2.0944 yd3. With 10% waste plan on 62.2036 cu ft, 2.304 yd3. Exact bag totals 192 40-lb, 128 60-lb, 96 80-lb; planning totals 208 40-lb, 140 60-lb, 104 80-lb.
Bag Count Estimate
- 26 bags of 80 lb concrete mix
- 35 bags of 60 lb concrete mix
- 52 bags of 40 lb concrete mix
Always verify the actual yield on the product label before buying materials.
Bag Counts by Waste Buffer for 36" diameter × 24" 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 | 14.14 | 24 | 32 | 48 |
| +5% typical DIY | 14.84 | 25 | 33 | 50 |
| +10% recommended | 15.55 | 26 | 35 | 52 |
| +15% rough conditions | 16.26 | 28 | 37 | 55 |
When Bagged Concrete vs Ready-Mix Makes Sense
For just one 36" × 24" footing the pour is small enough that bagged concrete is often simpler: you can mix a few batches and avoid scheduling a truck. The planning numbers with waste are 15.5509 cu ft (0.576 yd3) and 52 40-lb bags (or 35 60-lb / 26 80-lb bags).
If you're pouring several footings and the total climbs above a couple cubic yards, a ready-mix truck can be faster and more consistent. For a handful of footings, compare the total planning cubic yards to local minimum truck loads and weigh convenience versus the handling of multiple bags.
Common Uses for This Footing Size
This 36" diameter by 24" deep round footing is often used for isolated post supports where a narrow, cylindrical footing layout fits the plan — for example pergola posts, a single deck post on a corner, or a sign post with a limited footprint. The tube form keeps the pour neat and focused where vertical support is required.
Whether this size will support a given load depends on factors like applied load, soil bearing capacity, frost depth at your site, required reinforcement, and any permit conditions. It may work in some cases for deck or pergola posts, but final adequacy depends on those variables and engineering where needed.
Common Mistakes to Avoid
Common estimating and planning oversights to avoid for this round footing size:
- Using the tube diameter instead of finished footing diameter when calculating volume.
- Forgetting the 10% waste allowance and coming up short on the last batch.
- Ordering bag counts that are exact numbers instead of rounding up to whole bags.
- Not multiplying bag counts correctly when planning multiple footings.
- Failing to account for reinforcement displacement (rebar or post base) inside the form.
- Assuming ready-mix is always quicker without checking the total cubic yards needed.
Frequently Asked Questions
How much concrete is in a single 36-inch diameter by 24-inch deep footing?
One footing contains about 14.1372 cubic feet of concrete, which is 0.5236 cubic yards.
How many bags of concrete mix do I need for this footing?
Exact counts: 48 40-lb bags, 32 60-lb bags, or 24 80-lb bags. With a 10% waste allowance plan on 52 40-lb, 35 60-lb, or 26 80-lb bags.
Why add a 10% waste allowance and how does that change the numbers?
The 10% allowance covers spillage, minor over-excavation, and mixing loss. It increases the volume from 14.1372 cu ft to 15.5509 cu ft (0.5236 yd3 to 0.576 yd3) and bumps planned bag counts up to the listed planning numbers.
Will this footing size work for a deck or pergola post?
It may work in some cases for a deck or pergola post, but adequacy depends on the post load, soil bearing capacity, frost depth, and required reinforcement. Have the load and site conditions reviewed if there is any doubt.
Keep Planning Your Concrete Project
Use the calculator, compare more footing pages, and review your estimate before buying materials.
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.