Fence calculator: posts, panels and concrete
A 100 ft fence with 8 ft panels and one 4 ft gate needs 12 panels and 14 posts. Quikrete's rule sets each hole at 3 times the post width and a third of the post's height deep plus 6 in of gravel, so a 6 ft fence on 4x4 posts takes 2 bags of 80 lb mix per post.
Updated · By the Interior Redesign AI editorial team · Sources cited on the page
Fence posts
14 posts
12 panels, 28 bags of concrete in total.
Post holes
11 in wide
30 in deep incl. 6 in gravel
Concrete per post
2 bags
0.9 cu ft each
| Fence length without gate openings | 96 ft |
|---|---|
| Panels | 12 |
| Posts (sections + 1 per run + 1 per gate) | 14 |
| Post length to buy (height + depth, before gravel) | 8 ft |
| Concrete bags | 28 |
| Gravel for the hole bottoms | 0.16 cu yd |
Planning estimate. Posts often sit deeper than these rules where the ground freezes, and many towns limit fence height and set back lines: check with your building department and call 811 before you dig.
See your yard redesigned with AI
See a new fence line, gate and planting on a photo of your own yard before you dig the first hole.
The calculator is free with no account. AI renders need a free account: eligible new accounts get free credits once the email is verified (no card needed), and free results carry a small watermark.
Key numbers
- Hole diameter
- 3 × the post width: about 10.5 in for a 4x4, 16.5 in for a 6x6 (Quikrete)
- Hole depth
- 1/3 to 1/2 of the post's above-ground height, plus 6 in for gravel (Quikrete)
- Concrete level
- Fill to 3-4 in below the ground (Quikrete); we suggest topping it with soil or sod
- 80 lb bag yield
- About 0.60 cu ft (Quikrete Concrete Mix data sheet; Quikrete's post steps use Fast-Setting Concrete, which yields the same per pound)
- Posts
- One per section plus one per run, plus one per gate
Worked example
100 ft of 6 ft privacy fence with a gate
One run, 8 ft panels, one 4 ft gate, 4x4 posts set a third of their height deep, 80 lb bags.
- Fence without the gate: 100 − 4 = 96 ft. Panels: 96 ÷ 8 = 12.
- Posts: 12 + 1 (run) + 1 (gate) = 14.
- Hole: 3 × 3.5 in = 10.5 in wide; 72 in ÷ 3 = 24 in buried + 6 in gravel = 30 in deep.
- Concrete: (π × 5.25² − 3.5²) × 21 in ÷ 1,728 = 0.9 cu ft per post, 2 bags at 0.60 cu ft.
- Total: 14 posts × 2 = 28 bags. Posts are 8 ft long (72 in above ground + 24 in buried).
Order 12 panels, 14 posts at least 8 ft long and 28 bags of 80 lb concrete mix.
How we calculate
Layout: the fence length minus the gate openings, divided by the post spacing and rounded up, gives the panels or sections. Every straight run needs one post more than its sections, and every gate adds a post because it splits a run. Odd run lengths can add one more post per run, so walk your fence line before you order.
Holes and concrete: we follow Quikrete's post-setting steps: a hole three times the post's width, as deep as a third (or half) of the post's above-ground height plus 6 in for a compacted gravel bed, filled with concrete to 3 in below grade. Concrete per post is the hole cylinder minus the post, divided by the bag yield on Quikrete's data sheet.
Assumptions, labeled: post widths are the actual sizes of nominal posts (3.5 in for 4x4, 5.5 in for 6x6). For picket fences we count 2 rails per section up to 4 ft high and 3 above that, a common practice, not a code rule. Where the ground freezes, posts usually go below the frost line, which can be deeper than these rules.
Estimates, sources
Planning estimates and published guidelines, not quotes, designs or code rulings. Figures were checked on each source on the date shown. Local prices, your home and your jurisdiction's adopted code decide the real answer.
- Setting Posts: project instructions (Quikrete, as of Oct 26, 2026): hole diameter three times the width of the post; depth 1/3 to 1/2 of the post's above-ground length, plus 6 in; 6 in of gravel in the bottom; fill concrete to 3-4 in below ground level (undated page)
- QUIKRETE Concrete Mix (No. 1101) data sheet (Quikrete, as of Oct 26, 2026): yield per bag approximately 0.30 cu ft (40 lb), 0.375 (50 lb), 0.45 (60 lb), 0.60 (80 lb), 0.675 (90 lb); 4,000 psi at 28 days (sheet revised October 2022)
Posts and concrete for 100 feet of fence
One straight run, Quikrete hole rule at a third of the height, 80 lb bags.
| Fence | Sections | Posts | Concrete bags |
|---|---|---|---|
| 6 ft high, 8 ft panels, 4 ft gate | 12 | 14 | 28 |
| 6 ft high, 6 ft panels, 4 ft gate | 16 | 18 | 36 |
| 4 ft high, 8 ft sections, no gate | 13 | 14 | 14 |
| 6 ft high, 8 ft panels, 6x6 posts, no gate | 13 | 14 | 56 |
How to use this tool
Measure the fence line
Total length, the number of separate straight runs, and the gates.
Set the fence
Height, post spacing (panel width), post size and panels or pickets.
Choose the post depth
A third of the height is Quikrete's minimum; half is stiffer for tall or windy fences.
Read the list
Posts, panels or pickets and rails, hole size and concrete bags.
Questions
How many fence posts do I need for 100 feet?
With 8 ft panels and no gate, 14 posts; with 6 ft panels, 18. Each gate and each extra run adds a post.
How many bags of concrete per fence post?
For a 6 ft fence on 4x4 posts, Quikrete's hole rule gives about 0.9 cu ft per post: 2 bags of 80 lb mix. Taller fences and 6x6 posts need more.
How deep should a fence post hole be?
Quikrete's rule is 1/3 to 1/2 of the post's above-ground height, plus 6 in for gravel: 30 in for a 6 ft fence at the minimum. Go below the frost line where the ground freezes.
How wide should a fence post hole be?
Three times the post's width, says Quikrete: about 10.5 in for a 4x4 and 16.5 in for a 6x6.
How long should fence posts be?
The fence height plus the buried depth: an 8 ft post for a 6 ft fence set 2 ft deep. Buy longer posts if your frost line or soil calls for deeper holes.
Do I need a permit for a fence?
Often, and many towns cap fence height and set back lines. Check with your building department or HOA, and call 811 to locate buried utilities before you dig.
Numbers done. Now see it.
Same yard, same walls and windows, new finishes. Upload a photo of your own yard to compare looks before you buy anything.
