How Much Concrete for a 30-Inch Round Footing 48 Inches Deep?
Material planning for a 30-inch round footing (30" diameter × 48" deep) — cu ft, cu yd, and bag counts
Exact volumes and bag numbers for a 30-inch diameter sonotube footing 48 inches deep: 19.635 cu ft (0.7272 yd³) plus 10% waste planning counts for 40/60/80-lb bags.
Planning note: this is the material estimate for a narrow, 30" diameter × 48" deep round footing formed with a tube. The pour is small in volume but deep, so you’re ordering for a tall cylinder.
Expect 48 inches of excavation depth and a single-footing volume of 19.635 cubic feet. This page shows both the exact volume and the waste-adjusted bag counts used for ordering and staging materials.
Quick Answer
Exact volume: 19.635 cubic feet (0.7272 cubic yards).
Planning with 10% waste: 21.5985 cu ft (0.7999 yd³). Exact bag counts (no waste): 66 40-lb bags, 44 60-lb bags, 33 80-lb bags. Planning bag counts with 10% waste: 72 40-lb bags, 48 60-lb bags, 36 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 order for this 30" × 48" round footing:
- Confirm the footing diameter (30") and depth (48") at the location.
- Check the exact volume: 19.635 cu ft; use that for precise ordering if you will not allow waste.
- Add a 10% waste allowance to get 21.5985 cu ft for purchasing.
- Decide material type: bags of concrete mix for one or a few footings; ready-mix if you exceed several footings or need continuous pours.
- Round bag counts up to whole bags: planning counts are 72 (40-lb), 48 (60-lb), or 36 (80-lb).
- For multiple footings, multiply the planning volume and bag counts by the number of holes before placing orders.
Formula
Use this round footing formula:
Volume (ft³) = π × Radius (ft) × Radius (ft) × Depth (ft)
3.1416 × 1.25 × 1.25 × 4 = 19.64 ft³
19.64 ÷ 27 = 0.73 yd³
If you add a 10% waste allowance, you should plan closer to 0.8 cubic yards.
Worked Example
Single-footing example (before waste): 19.635 cu ft (0.7272 yd³). With 10% waste: 21.5985 cu ft (0.7999 yd³). Exact bag counts: 66 40-lb / 44 60-lb / 33 80-lb. Planning counts: 72 40-lb / 48 60-lb / 36 80-lb.
Multiple-footing example — 3 identical footings: total 58.905 cu ft, 2.1816 yd³. Planning bags (10% waste): 216 40-lb bags, 144 60-lb bags, 108 80-lb bags.
Bag Count Estimate
- 36 bags of 80 lb concrete mix
- 48 bags of 60 lb concrete mix
- 72 bags of 40 lb concrete mix
Always verify the actual yield on the product label before buying materials.
Bag Counts by Waste Buffer for 30" diameter × 48" 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 | 19.64 | 33 | 44 | 66 |
| +5% typical DIY | 20.62 | 35 | 46 | 69 |
| +10% recommended | 21.6 | 36 | 48 | 72 |
| +15% rough conditions | 22.58 | 38 | 51 | 76 |
When Bagged Concrete vs Ready-Mix Makes Sense
For a single 30" × 48" tube pour, bagged concrete is straightforward: you can mix a few dozen bags on site and pour a single cylinder without waiting for a truck. The total is under 1 cubic yard, so bags avoid minimum truck orders.
If you have several of these footings (three or more), the total volume quickly passes 1–2 cubic yards and ready-mix becomes more practical to save time and mixing effort. Use the planning totals to compare supplier minimums and mixing time before deciding.
Common Uses for This Footing Size
This 30" diameter × 48" deep footing is sized for isolated cylindrical supports where a narrow footprint fits the layout. It is often used for single post supports, pergola posts, deck posts in compact layouts, or sign supports when a tall, narrow footing is desired.
Actual suitability depends on applied load, soil bearing capacity, frost depth, and reinforcement. Your building department may have specific depth or reinforcement requirements that affect whether this diameter and depth are sufficient for the intended load.
Common Mistakes to Avoid
Common estimating and ordering mistakes to avoid:
- Mixing inches and feet when computing radius or depth—keep units consistent (radius = 1.25 ft here).
- Forgetting the 10% waste allowance and under-ordering bags.
- Ordering bag counts as fractional numbers instead of rounding up to whole bags.
- Assuming exact bag counts cover field spillage or small overpour without a buffer.
- Not multiplying both volume and bags when ordering for multiple footings.
- Failing to confirm your building department’s minimum footing depth or reinforcement expectations before finalizing plans.
Frequently Asked Questions
What is the exact concrete volume for a 30-inch diameter, 48-inch deep round footing?
The exact volume is 19.635 cubic feet, which is 0.7272 cubic yards.
How many bags of concrete mix do I need for this footing?
Exact counts (no waste): 66 40-lb bags, 44 60-lb bags, or 33 80-lb bags. With a 10% waste allowance plan on 72 40-lb, 48 60-lb, or 36 80-lb bags.
Why add a 10% waste allowance to the volume?
The 10% allowance covers spillage, slight over-excavation, and mixing losses. It’s a simple buffer to reduce the chance of running short during the pour.
Is this footing size adequate for a deck post or pergola column?
This size may work in some cases for isolated posts and pergola columns, but adequacy depends on the post load, soil bearing, frost depth, and required reinforcement. Confirm requirements with structural guidance and the building department for your project.
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.