How Much Concrete for an 8-Inch Round Footing 48 Inches Deep?
Material takeoff for an 8" diameter × 48" deep round footing: cubic feet, cubic yards, and bag counts
Exact and planning amounts for an 8" diameter × 48" deep round footing: 1.3963 cu ft (0.0517 yd3), exact bag counts, and a 10% waste-adjusted plan.
At 8" diameter × 48" deep this is a narrow, deep tube-form footing that pours roughly one and four-tenths cubic feet of concrete. The depth here is significant: 48" of excavation and a 4-ft concrete column inside the tube.
This page shows the exact volume for one footing, the planning volume with a 10% waste allowance, and the bag counts you’ll likely order. It’s written to help you decide between bagged concrete and a vehicle delivery when you have one or multiple of these 8" sonotube footings to pour.
Quick Answer
Exact volume: 1.3963 cubic feet (0.0517 cubic yards) for one 8" diameter × 48" deep round footing.
Planning with 10% waste: 1.5359 cubic feet (0.0569 cubic yards). Exact bag counts: 5 40-lb bags, 4 60-lb bags, or 3 80-lb bags. Waste-adjusted planning bag counts: 6 40-lb bags, 4 60-lb bags, or 3 80-lb bags.
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How to Use This Footing Estimate
Quick steps to estimate and order material for this footing size.
- Confirm the tube inside diameter is 8" and depth is 48" before you calculate.
- Use the known volume per footing (1.3963 cu ft) to check your totals for multiple footings.
- Add a 10% waste allowance (planning volume 1.5359 cu ft) and pick the bag size you prefer.
- Decide between bagged concrete for single pours or a delivered mix when total yards grow larger.
- Round up bag counts to whole bags and double-check delivery timing if you order bags or mix by drum.
- Note reinforcement or rebar needs separately when you finalize design and order quantities.
Formula
Use this round footing formula:
Volume (ft³) = π × Radius (ft) × Radius (ft) × Depth (ft)
3.1416 × 0.33 × 0.33 × 4 = 1.4 ft³
1.4 ÷ 27 = 0.05 yd³
If you add a 10% waste allowance, you should plan closer to 0.06 cubic yards.
Worked Example
Single footing example: before waste the volume is 1.3963 cu ft (0.0517 yd3). With a 10% allowance the planning volume is 1.5359 cu ft (0.0569 yd3). Exact bag counts for one footing are 5 40-lb bags, 4 60-lb bags, or 3 80-lb bags; with waste plan on 6 40-lb, 4 60-lb, or 3 80-lb.
Multiple-footing example (four footings): total = 5.5852 cu ft, 0.2068 yd3. Exact total bags = 20 40-lb bags (or 16 60-lb, or 12 80-lb). With 10% waste the total planning volume is 6.1436 cu ft (0.2276 yd3) and planning bags are 24 40-lb, 16 60-lb, or 12 80-lb.
Bag Count Estimate
- 3 bags of 80 lb concrete mix
- 4 bags of 60 lb concrete mix
- 6 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 8" × 48" tube the total is only 1.3963 cu ft (0.0517 yd3). That small a volume is usually easier to handle with bagged concrete — buy the few 40-, 60-, or 80-lb bags and mix in a wheelbarrow or mixer.
If you have several of these footings the math changes. Four footings still total only about 0.23 yd3 with waste, which is below most ready-mix truck minimums, so bags often remain simpler. When your total pour approaches a full truckload (typically close to 1 yd3 or more) a ready-mix order becomes worth comparing.
Common Uses for This Footing Size
An 8" diameter × 48" deep round footing suits narrow, isolated supports where a compact cylindrical footprint is required. Typical applications include single post supports for small pergolas, signposts, or deck posts in a layout that uses multiple narrow piers rather than wide pads.
Limits depend on load, soil bearing capacity, frost depth, and whether the footing is reinforced. For heavier columns or poor soils a larger diameter and added reinforcement may be needed, and you should check local permitting and plan requirements before finalizing the design.
Common Mistakes to Avoid
Common estimating and ordering mistakes to avoid for an 8" × 48" round footing.
- Mixing inches and feet when calculating volume — use the provided feet values.
- Forgetting the 10% waste allowance and ordering exactly the calculated amount.
- Confusing exact bag counts with the waste-adjusted planning counts.
- Measuring the tube outside diameter instead of the clear inside diameter used for volume.
- Rounding bag counts down instead of up when converting fractional bag needs to whole bags.
- Not adding separate allowance for reinforcement or embedded items when ordering materials.
Frequently Asked Questions
What is the exact concrete volume for one 8" diameter × 48" footing?
One 8" diameter × 48" footing requires 1.3963 cubic feet of concrete, which equals 0.0517 cubic yards.
How many sacks of bagged concrete do I need for this footing?
Exact counts for one footing are 5 40-lb bags, 4 60-lb bags, or 3 80-lb bags. With a 10% waste allowance plan on 6 40-lb bags, 4 60-lb bags, or 3 80-lb bags.
Why add a 10% waste allowance instead of ordering exact volume?
A 10% waste allowance covers spillage, overage during placement, and minor measurement differences so you don’t run short on a small pour.
Is this footing size adequate for a deck post or pergola column?
This 8" × 48" footing may work in some cases for isolated deck or pergola posts, but adequacy depends on the applied load, soil bearing capacity, frost depth, and whether reinforcement is required.
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.