Fence Post Concrete Reference Chart
Everything you need to size a fence post pour lives on this one page: hole diameter by post size, depth by fence height and climate, bag counts across every combination, bag yield by size, and total bags for a full fence line. Find your row, read across, done.
Quick answer
Most residential fence posts land in the same range: a 4×4 post in a 10 in hole, 24 in deep needs about 2 bags of 80 lb concrete. A 6×6 post in a 16 in hole, 30 in deep needs about 6 bags. Every chart below breaks that down further by exact size and depth.
For your exact numbers, the Fence Post Concrete Calculator runs the same math as every chart on this page instantly.
Chart 1: Hole diameter by post size
| Post size | Actual dimensions | Line post hole | Gate / corner post hole |
|---|---|---|---|
| 4×4 | 3.5 × 3.5 in | 8-10 in | 12 in |
| 6×6 | 5.5 × 5.5 in | 12-14 in | 16-18 in |
| Round post (4 in) | 4 in diameter | 10-12 in | 14 in |
Chart 2: Depth by fence height and climate
| Fence height | Mild climate (frost <12 in) | Cold climate (frost 36-48 in) |
|---|---|---|
| 4 ft | 16-18 in | 42-54 in |
| 6 ft | 24 in | 48-54 in |
| 8 ft | 32 in | 48-60 in |
Full explanation and regional frost depth data: How Deep Should a Fence Post Hole Be?
Chart 3: Bag yield (coverage) by size
| Bag size | Yield |
|---|---|
| 40 lb | 0.30 cu ft |
| 50 lb | 0.375 cu ft |
| 60 lb | 0.45 cu ft |
| 80 lb | 0.60 cu ft |
| 90 lb | 0.675 cu ft |
Chart 4: Bags needed, 4×4 post
Post volume already subtracted, 10% waste included. 80 lb / 50 lb bags shown.
| Hole diameter | 18 in deep | 24 in deep | 30 in deep | 36 in deep |
|---|---|---|---|---|
| 8 in | 1 / 2 | 1 / 2 | 2 / 3 | 2 / 3 |
| 10 in | 2 / 3 | 2 / 3 | 3 / 4 | 3 / 5 |
| 12 in | 2 / 4 | 3 / 5 | 4 / 6 | 4 / 7 |
Each cell reads as 80 lb bags / 50 lb bags. Full worked examples: How Much Concrete for a 4×4 Fence Post?
Chart 5: Bags needed, 6×6 post
Post volume already subtracted, 10% waste included. 80 lb / 50 lb bags shown.
| Hole diameter | 24 in deep | 30 in deep | 36 in deep | 48 in deep |
|---|---|---|---|---|
| 12 in | 3 / 4 | 3 / 5 | 4 / 6 | 5 / 7 |
| 14 in | 4 / 6 | 4 / 7 | 5 / 8 | 7 / 11 |
| 16 in | 5 / 7 | 6 / 9 | 7 / 11 | 9 / 14 |
| 18 in | 6 / 10 | 8 / 12 | 9 / 14 | 12 / 19 |
Chart 6: Total bags for a full fence line
Based on 4×4 posts, 10 in holes, 24 in deep (2 bags of 80 lb per post) — post count includes one extra post to close each run.
| Fence length | 6 ft spacing | 8 ft spacing | 10 ft spacing |
|---|---|---|---|
| 50 ft | 10 posts / 20 bags | 8 posts / 16 bags | 7 posts / 14 bags |
| 100 ft | 18 posts / 36 bags | 14 posts / 28 bags | 11 posts / 22 bags |
| 150 ft | 26 posts / 52 bags | 20 posts / 40 bags | 16 posts / 32 bags |
| 200 ft | 34 posts / 68 bags | 26 posts / 52 bags | 21 posts / 42 bags |
Add extra bags separately for any gate or corner posts, which typically use a wider hole than the line posts counted here.
Get your exact combination.
Enter your own post size, hole dimensions, and post count for an instant bag count.
Use the free Fence Post Concrete CalculatorHow to use this page
- Start with Chart 1Confirm the right hole diameter for your post size and role (line vs. gate/corner).
- Then Chart 2Set your depth using your fence height and local climate.
- Then Chart 4 or 5Match your post size, hole diameter, and depth to a bag count directly.
- Then Chart 6Scale a single post’s number up to your whole fence line.
Mistakes when reading a reference chart
- Using nominal post size instead of actualThese charts already use actual dimensions (3.5 in for a “4×4”) — don’t re-round to the nominal size on top of that.
- Applying line-post numbers to gate or corner postsThose need their own row, from a wider hole diameter.
- Skipping straight to the bag chart without checking depth firstThe wrong depth row gives the wrong bag count, even with the right post and hole size.
- Forgetting to add extra posts for a closed loop or complex layoutChart 6 assumes a straight run — corners and returns need their own count.
- Rounding a chart figure downEvery number here is already rounded up to a whole bag — don’t round down further to save a bag.
What these charts assume, and when to recalculate
- 10% waste allowanceBuilt into every bag figure — increase it yourself for rocky or uneven digging.
- Standard 80 lb yield (0.60 cu ft)Confirm against your specific bag’s label, since yield can vary slightly by brand.
- A straight fence runChart 6 doesn’t account for corners, gates, or non-linear layouts — add those separately.
- Average frost depth rangesChart 2 is a starting point — always confirm your exact local frost line before finalizing depth.
Find your total in five steps
- Confirm post size and role (line vs. gate/corner) using Chart 1.
- Set your depth using Chart 2 and your local frost line.
- Look up your bag count in Chart 4 (4×4) or Chart 5 (6×6).
- Scale to your full fence with Chart 6, or your own post count.
- Add extra for gate and corner posts calculated separately.
Frequently asked questions
Which chart do I need if I just want a quick number?
Chart 4 for a 4×4 post, or Chart 5 for a 6×6 — match your hole diameter and depth to get a bag count directly.
Do these charts already account for the post’s own volume?
Yes. Every bag figure has the post’s actual cross-section already subtracted from the hole volume, plus a 10% waste allowance.
How do I calculate a whole fence line, not just one post?
Use Chart 6 for a straight run at standard 4×4/10 in/24 in dimensions, or multiply your own per-post figure from Chart 4 or 5 by your total post count.
Do gate and corner posts use the same chart?
They use the same charts, but at a wider hole diameter — look up the gate/corner column in Chart 1, then find that hole size in Chart 4 or 5.
What if my post or hole size isn’t listed?
Use the Fence Post Concrete Calculator for any exact combination not covered here, or follow the step-by-step formula in How to Calculate Concrete for Fence Posts.
Why do the 50 lb numbers look so much higher than the 80 lb ones?
A 50 lb bag yields less than half the volume of an 80 lb bag (0.375 vs 0.60 cu ft), so it naturally takes more bags to fill the same hole.
How accurate are these charts for my specific brand of concrete?
Very close for standard mix, but always check your bag’s printed yield — it can vary slightly by brand and product line.
Do these charts work outside the US, in kg and metric measurements?
The dimensions and formulas are unit-independent, but the bag sizes shown (40-90 lb) are standard US sizing. For kg-based cement bags, see How Many CFT is One Bag of Cement?
Related reading
Get your exact bag count
Enter your post size, hole dimensions, and post count for an instant, accurate bag count.
Open the Fence Post Concrete Calculator