Get the concrete for fence posts, less the post.
⚙️Calculation Parameters
📊Calculated Output
How Fence Post Concrete Calculator Works?
To estimate fence post concrete, the Fence Post Concrete Calculator subtracts the post from each hole and multiplies by the number of posts. The process takes 4 steps.
Enter the fence run
Type the fence length and post spacing, often 6 ft or 8 ft (1.8 m or 2.4 m). The calculator counts posts as length ÷ spacing + 1.
Enter hole size
Type the hole diameter and depth. A common rule sets the hole width at 3 times the post width and depth at one-third of the post height above ground.
Pick the post
Choose wood 4×4 or 6×6, or round steel, to subtract its volume.
Read bags
The tool shows concrete per post and total bags of 50 lb fast-setting or standard mix.
Fence Post Concrete Calculator Formula
The Fence Post Concrete Calculator uses hole minus post, times post count.
Post count
n = ⌈L ÷ s⌉ + 1L is fence length and s is post spacing.
Concrete per post
V = π × (D ÷ 24)² × (H ÷ 12) − V_postHole minus post.
Total bags
Bags = ⌈n × V ÷ Y⌉Y = 0.375 ft³ for 50 lb.
Worked example: 120 ft fence, 8 ft spacing, 10 in × 30 in holes, 4×4 posts
- n = 120 ÷ 8 + 1 = 16 posts
- V = 1.364 − 0.213 = 1.151 ft³ per post
- Bags = ⌈16 × 1.151 ÷ 0.375⌉ = 50 bags of 50 lb
Fence Post Concrete Calculator Conversion Table
The fence post conversion table lists net concrete and 50 lb (23 kg) bags for 5 post types, per post and for a 20-post fence.
| Post | Hole | Net ft³ per post | 50 lb bags per post | 50 lb bags for 20 posts |
|---|---|---|---|---|
| 4×4 wood, 4 ft fence | 10 in × 24 in | 0.921 | 3 | 50 |
| 4×4 wood, 6 ft fence | 10 in × 30 in | 1.151 | 4 | 62 |
| 6×6 wood gate post | 12 in × 36 in | 1.726 | 5 | 93 |
| 2-3/8 in steel line post | 8 in × 24 in | 0.637 | 2 | 34 |
| 2-7/8 in steel terminal post | 10 in × 36 in | 1.501 | 5 | 81 |
Crown the concrete top to shed water away from wood posts.
What is Fence Post Concrete Calculator?
A Fence Post Concrete Calculator is a fence-specific calculator that estimates concrete per post and for the whole fence line, net of post displacement.
Fence jobs repeat the same hole dozens of times, so small errors multiply. A 4×4 post fills 16% of a 10 in hole, and ignoring the post overstates the concrete by the same share. Over a 16-post fence, that is several extra bags. The calculator subtracts the post and counts posts from the fence length.
Fast-setting mix is common for fence posts. The calculator uses its 0.375 ft³ yield per 50 lb bag by default.
What are the uses of Fence Post Concrete Calculator?
There are 4 main uses of the Fence Post Concrete Calculator.
Wood privacy fences
Installers count bags for 4×4 line posts.
Chain-link fences
Crews size holes for steel line and terminal posts.
Gate posts
Builders size larger holes for heavy gate posts.
Fence quotes
Contractors price concrete per linear foot of fence.
🔗Related Sonotube Calculators
View all 106 subtools →Deck Pier Concrete Calculator
Get the concrete for your deck piers.
Pergola Pier Concrete Calculator
Get the concrete for pergola piers.
Porch Pier Concrete Calculator
Get the concrete for porch piers.
Pier-and-Beam Concrete Calculator
Add up the piers under a pier and beam home.