Fence Post Calculator
Fence Post Results
| Hole Diameter | Depth 24" | Depth 36" | Depth 48" |
|---|---|---|---|
| 8 inches | 0.5 bags | 0.7 bags | 1 bag |
| 10 inches | 0.8 bags | 1 bag | 1.5 bags |
| 12 inches | 1 bag | 1.5 bags | 2 bags |
Rent a two-man power auger from Home Depot or Lowes for $80–$120/day — it's worth every penny. Hand digging post holes is exhausting and produces uneven walls that don't grip concrete as well. The hole should be 3× the post width: 8–10 inches for a 4×4 post, 12 inches for a 6×6. Flare the bottom of each hole slightly wider — this "bell" shape resists frost heave in cold climates.
Always use pressure-treated lumber rated for ground contact — look for the UC4B or UC4C stamp on the tag. UC4A is only rated for above-ground use. Standard #2 pine will rot in 3–5 years in direct soil contact regardless of paint or sealant. Western red cedar and black locust are naturally rot-resistant alternatives but cost significantly more. Never set untreated wood directly in concrete.
Place post, pour dry mix into hole, add water slowly. No mixing required. Sets in 20–40 minutes. You can attach rails in 4 hours. Best for most DIY fence projects. Works in wet conditions too — just reduce added water.
Mix in a wheelbarrow and pour wet. Takes 24–48 hours to set. Better for gate posts and corner posts under heavy load. Use 3000 PSI concrete for all posts. Check for plumb before it sets — you have about 30 minutes to make adjustments.
Fence Post Concrete — Bags Per Post Reference
| Post Size | Hole Diameter | 24" deep | 36" deep | 48" deep |
|---|---|---|---|---|
| 4×4 post | 9–10" | 1 bag | 2 bags | 2 bags |
| 6×6 post | 12" | 1 bag | 2 bags | 3 bags |
| Round 4" post | 10" | 1 bag | 2 bags | 2 bags |
| Gate post 6×6 | 16" | 2 bags | 3 bags | 4 bags |
Rule of thumb: the hole should be 3× the post diameter and at least 1/3 the post height deep. For a 6-foot fence panel, the posts should be 9 feet long with 3 feet buried. In frost-prone areas, always dig below the local frost line — a post set above the frost line will heave out of the ground over winter.
Quikrete Fast-Setting Concrete is the best choice for fence posts. Pour the dry mix directly into the hole, add water on top, and it sets in 20–40 minutes. You do not need to mix it first. This lets you set 10–15 posts in a day and hang panels the next morning.
How Much Concrete for a 4x4 Post — Quick Reference
The most-searched fence post question, answered with exact bag counts:
| 4x4 Hole Depth | Hole Diameter | 50 lb Fast-Set | 80 lb Standard |
|---|---|---|---|
| 24 inch | 10 inch | 2 bags | 1 bag |
| 36 inch (standard) | 10 inch | 3 bags | 2 bags |
| 48 inch (frost line) | 12 inch | 5 bags | 3 bags |
For a standard 6-foot privacy fence with 4x4 posts at 8-foot spacing, a 100-foot fence run needs about 13 posts. At 36-inch hole depth with 80lb concrete, you need 26 bags of concrete total.