How Much Concrete for a 12-Inch Round Footing 48 Inches Deep?
12" diameter × 48" deep round footing — 3.1416 cu ft, 0.1164 yd³ and bag counts for planning
Exact volume and bag counts for a 12" diameter by 48" deep Sonotube-style footing: 3.1416 cu ft (0.1164 yd³). Includes planning numbers with a 10% waste allowance and bag totals.
This is a narrow tube-form footing sized 12" diameter × 48" deep. It’s a small-volume, cylindrical pour that holds 3.1416 cubic feet of concrete — enough for a single isolated post base.
Depth is 48" and the radius used here is 0.5 ft. Use the bag counts on this page for ordering or mixing on site; for heavier loads or unusual soils get a site-specific design or engineer input.
Quick Answer
Exact volume: 3.1416 cubic feet (0.1164 cubic yards). Exact bag counts: 11 40-lb bags, 7 60-lb bags, or 6 80-lb bags for the single footing as poured.
Planning with 10% waste: 3.4558 cubic feet (0.128 cubic yards). Planning bag counts: 12 40-lb bags, 8 60-lb bags, or 6 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 prepare material for this 12" × 48" round footing.
- Confirm the diameter (12") and depth (48") at the location.
- Compare the exact volume (3.1416 cu ft) to what you need for multiple footings.
- Add the 10% waste allowance to create the planning volume of 3.4558 cu ft.
- Decide between bagged concrete or ready-mix based on count and access.
- Order or gather the counted bags (40/60/80 lb) using the planning numbers.
- If pouring several footings, multiply planning volumes and bag counts before purchasing.
Formula
Use this round footing formula:
Volume (ft³) = π × Radius (ft) × Radius (ft) × Depth (ft)
3.1416 × 0.5 × 0.5 × 4 = 3.14 ft³
3.14 ÷ 27 = 0.12 yd³
If you add a 10% waste allowance, you should plan closer to 0.13 cubic yards.
Worked Example
Single footing — before waste: 3.1416 cu ft (0.1164 yd³). Exact bag counts: 11 40-lb, 7 60-lb, or 6 80-lb. With 10% waste: 3.4558 cu ft (0.128 yd³) and planning bags: 12 40-lb, 8 60-lb, or 6 80-lb.
Three footings — before waste: 9.4248 cu ft (0.3492 yd³). Exact bags total: 33 40-lb, 21 60-lb, 18 80-lb. With 10% waste: 10.3674 cu ft (0.384 yd³) and planning bags: 36 40-lb, 24 60-lb, 18 80-lb.
Bag Count Estimate
- 6 bags of 80 lb concrete mix
- 8 bags of 60 lb concrete mix
- 12 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 12" × 48" footing, bagged concrete is usually simpler: you can mix a few 40/60/80 lb bags and place a small pour without a truck. The counts here show the handful of bags required.
When you run multiple footings (several pours), ready-mix starts to make sense because it saves mixing time and gives consistent slump. Use the planning cubic yard totals to decide if a small truck or volumetric pour is worth arranging.
Common Uses for This Footing Size
This 12" diameter × 48" footing is suited to narrow isolated post supports: pergola posts, deck posts in tight layouts, sign posts, or similar cylindrical footing arrangements where a small footprint is desired. It’s the kind of pour used when a narrow tube form is preferred over a wide pad.
Limits depend on load, soil bearing capacity, frost depth, and whether reinforcement is required. For heavier loads, deeper frost conditions, or where permits require engineered details, get a site-specific design or an engineer’s input before relying on this size alone.
Common Mistakes to Avoid
Common estimating and ordering mistakes to avoid for this footing size.
- Using the diameter instead of the radius in the formula, which underestimates volume.
- Forgetting the 10% waste allowance and coming up short on site.
- Mixing bag counts from different bag weights without clear totals (keep one bag size per calculation).
- Failing to multiply bag counts correctly when ordering multiple footings.
- Rounding down cubic yards too aggressively and losing margin on small pours.
- Not planning how mixed concrete will be transported to the Sonotube before it sets.
Frequently Asked Questions
What is the exact concrete volume for a 12" diameter by 48" deep footing?
The exact volume is 3.1416 cubic feet, which equals 0.1164 cubic yards.
How many bags of concrete do I need for one 12" × 48" footing?
Exact counts: 11 40-lb bags, 7 60-lb bags, or 6 80-lb bags. For ordering include the 10% waste planning counts: 12 40-lb, 8 60-lb, or 6 80-lb.
Why use a 10% waste allowance for this footing?
Ten percent accounts for small overpour, waste, and slight measurement or mixing variations on a small round pour.
Is a 12" diameter × 48" footing adequate for a deck post or pergola column?
It is sometimes used for deck or pergola posts in narrow layouts, but actual adequacy depends on the applied load, soil bearing capacity, frost depth, and whether reinforcement is specified.
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.