How Much Concrete for a 16-Inch Round Footing 48 Inches Deep?
Estimate for a 16" diameter × 48" deep round footing — cubic feet, cubic yards, and bag counts
Volume and bag estimates for a 16" diameter, 48" deep Sonotube-style footing: exact volume, 10% waste planning volume, and bag counts for 40-, 60-, and 80-lb mixes.
This is a narrow, tube-form footing sized at 16" diameter × 48" deep. It’s a small cylindrical pour commonly used as an isolated post support for a deck or pergola post layout where a tight footprint is needed.
Plan on sinking a 48" deep tube and filling roughly 5.6 cubic feet of concrete. If you’re buying bagged concrete for one pour, the bag counts below include the usual small waste allowance. For larger layouts, multiply the numbers or use a ready-mix quote.
Quick Answer
Exact volume: 5.5851 cubic feet (0.2069 cubic yards).
Planning with 10% waste: 6.1436 cubic feet (0.2276 cubic yards). Plan on 21 40-lb bags, or 14 60-lb bags, or 11 80-lb bags for the waste-adjusted single footing.
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 concrete for this 16" × 48" round footing:
- Measure the actual tube depth and diameter on site; use 16" diameter × 48" deep for this estimate.
- Confirm the exact volume: 5.5851 cu ft (0.2069 yd3) per footing before waste.
- Add a waste allowance (10% used here) to get 6.1436 cu ft per footing for ordering.
- Decide between bagged concrete (bags of concrete mix) or ready-mix based on quantity — bag counts shown below are for single footing planning.
- If ordering multiple footings, multiply the planning volume and bag counts by the number of footings before placing the order.
- Round up bag counts to whole bags and verify truck or supplier lead time if using ready-mix for grouped pours.
Formula
Use this round footing formula:
Volume (ft³) = π × Radius (ft) × Radius (ft) × Depth (ft)
3.1416 × 0.67 × 0.67 × 4 = 5.59 ft³
5.59 ÷ 27 = 0.21 yd³
If you add a 10% waste allowance, you should plan closer to 0.23 cubic yards.
Worked Example
Single-footing example: before waste the footing is 5.5851 cu ft (0.2069 yd3). With 10% waste plan on 6.1436 cu ft (0.2276 yd3) and 21 40-lb bags (or 14 60-lb, or 11 80-lb bags).
Multiple-footing example (four footings): before waste totals are 22.3404 cu ft (0.8276 yd3) and 76 40-lb bags (or 52 60-lb, or 40 80-lb) exactly. With 10% waste the totals are 24.5744 cu ft (0.9104 yd3) and 84 40-lb bags (or 56 60-lb, or 44 80-lb).
Bag Count Estimate
- 11 bags of 80 lb concrete mix
- 14 bags of 60 lb concrete mix
- 21 bags of 40 lb concrete mix
Always verify the actual yield on the product label before buying materials.
When Bagged Concrete vs Ready-Mix Makes Sense
For a single 16" × 48" footing, bagged concrete is often simpler: you can mix on-site and only need about 21 40-lb bags (or the equivalent in 60- or 80-lb bags). Small deliveries and hand mixing avoid waiting for a truck for a single short pour.
If you have several footings close together (four or more), ready-mix starts to make sense because it reduces on-site mixing time and gives a continuous pour. For mid-size counts, compare the total yardage and the cost and timing of a small ready-mix truck versus buying and mixing bags.
Common Uses for This Footing Size
This 16" diameter, 48" deep round footing is typically used for isolated post supports where the footprint is narrow: pergola posts, deck post locations on tight layouts, small sign supports, and similar single-point supports. The tube form keeps the pour cylindrical and saves excavation width where space is limited.
Limits come down to applied load, soil bearing capacity, frost depth, and whether you need rebar or concrete cover. For heavier loads or weak soils you’ll likely need a larger diameter, added reinforcement, or a different footing layout; those details affect structural adequacy more than raw volume does.
Common Mistakes to Avoid
Common estimating and ordering mistakes to avoid:
- Ordering exactly the calculated volume without adding any waste — always include an allowance.
- Mixing bag types interchangeably without checking yield differences between 40-, 60-, and 80-lb bags.
- Forgetting to multiply bag counts when planning multiple footings.
- Assuming the tube will be filled to the exact top; account for form overlap and finishing clearance.
- Not rounding bag counts up to whole bags when placing the order.
- Failing to confirm delivery timing if you switch from bags to ready-mix for multiple pours.
Frequently Asked Questions
What is the exact concrete volume for a 16" diameter × 48" deep round footing?
The exact volume is 5.5851 cubic feet, which equals 0.2069 cubic yards.
How many bags of concrete do I need for one footing?
Exact bag counts are 19 40-lb bags, 13 60-lb bags, or 10 80-lb bags before waste. With a 10% planning allowance use 21 40-lb, 14 60-lb, or 11 80-lb bags.
Why include a 10% waste allowance and how much does that add?
A 10% waste allowance covers spillage, slight over-excavation, and finishing waste. For this footing it raises the single-footing volume from 5.5851 cu ft to 6.1436 cu ft (0.2069 yd3 to 0.2276 yd3).
Is this footing size adequate for a deck or pergola post?
This size is sometimes used for deck or pergola posts and may work in some cases, but adequacy depends on the post load, soil bearing capacity, frost depth, and reinforcement. Confirm structural requirements for the specific load and site conditions.
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.