Concrete Calculator: How Much Concrete Do You Need for Chain Link Fence Posts & Footings?
Whether you’re setting a few line posts for a backyard fence or anchoring heavy-duty corner and gate posts, getting the concrete amount right prevents delays, extra trips, and wobbly posts. This guide walks you through the basic formula, fence-specific dimensions, and bag vs. ready-mix choices. With a walkthrough example using common post-hole sizes, this guide is your concrete calculator for chain-link fence posts and footings.
Why Estimate Concrete Before You Order?
Estimating concrete before you start your fence project saves time, money, and frustration. Running out of concrete mid-pour can lead to weak joints and misaligned posts, while over-ordering adds unnecessary cost. Knowing your total volume also helps you decide whether bagged or ready-mix is a better choice (Tip! Most pros tend to switch to ready-mix when the job exceeds about one cubic yard). Accurate calculations ensure you meet depth and diameter requirements for structural integrity, especially in areas where proper sizing prevents seasonal movement and premature failure.
The Basic Formula for Concrete Volume
Most fence posts are cylinders, and go into cylindrical holes
Concrete = (π × r[hole]^2 × h) - ( π × r[post]^2 × h)
When doing this calculation, reserve 4-6″ of the hole for compacted gravel at the bottom for easy drainage, and subtract that from h when you measure your concrete depth.
An Example of Fencing
- 8″ / 2 = 4″ = 0.333 ft
- h: 30″ - 4″ gravel = 26″ = 2.167 ft
- π × 0.333^2 × 2.167 ≈ 0.756 ft³
- (2.375″ OD): 1.1875″ = 0.099 ft
- π × 0.099^2 × 2.167 ≈ 0.067 ft³
- 0.756 - 0.067 = 0.689 ft³
- 0.689/0.45≈1.53 → 2 bags (add 5 - 10% waste: still 2)
Standard 2 ⅜″ Line Post (6' fence), hole 8″ × 30″, with 4″ gravel
Step 1: Calcualte Hole Radius
Step 2: Calcualte Concrete Depth
Step 3: Calculate Hole Volume
Step 4: Calcualte Post Radius
Step 5: Calculate Post Volume
Step 6: Calcualte Concrete Volume
Step 7: Calculate Bags Needed (60 lb Bag in this Case)
Note: To Convert Concrete Volume into Bags, do the following: Concrete Volume (ft³) / Bag Yield (ft³)
Bags vs Ready-Mix - Which Should You Use?
Now that you know how much concrete you'll need, the next question you might be asking is which type of concrete should you use? The following table provides some information on the two main types of concrete: concrete bags and ready-mix. Concrete bags are bags you can buy and mix yourself, while ready-mixed concrete is already made by an outside company and delivered to you.
| Concrete Bags | Ready-Mix Concrete |
|---|---|
| Best for Small and Medium Projects | Best for Large Projects |
| Only Mix What You Need | Need to Coordinate Times for Minimal Orders |
| Setting Time Can Vary Based on Mix | Consistent Mix and Faster Setting |
Best Practices for Chain Link Fences
- Have a Gravel Base (4"-6") for Drainage
- Flare Bottoms of Posts in Frost-Prone Areas to Resist Heave
- Slope Concrete Top Away from Posts to Have Water Drip Away from the
- Always Verify Your Spacing for Posts
- Adjust your Holes and Concrete for Taller Fences
Here are some additional tips for installing chain link fencing with concrete:
