Fence Calculator
Enter the length and height of your fence, the post spacing and any gates to get posts, rails, pickets, fasteners and the concrete for every post hole.
Enter the fence length, height and post spacing.
On this page
How to use the fence calculator
- Measure the total run of the fence along the property line or layout string, including the gate openings.
- Set the height, post spacing and number of gates. Each gate opening and each corner adds a post.
- Enter the picket width and gap. A privacy fence has no gap; a classic picket fence might use a 2½ to 3 inch gap.
- Set the post holes to match your post size, fence height and frost depth, and read how much concrete to buy.
How to calculate fence materials
Worked example: 100 ft of 6 ft privacy fence with one 4 ft gate
- Sections: (100 − 4) ÷ 8 = 12 → posts: 12 + 1 + 1 = 14 posts (8 ft long for 2 ft holes)
- Rails: 12 sections × 3 = 36 rails of 8 ft
- Pickets: 1,200 in ÷ 5.5 in = 219, plus 5% = 230 pickets
- Concrete: a 10 in hole 24 in deep with a 4×4 post holds 0.92 ft³ → 14 holes need 12.9 ft³, or 22 bags of 80 lb (about 1.5 per hole).
Post spacing, depth and hole size
| Fence height | Typical post length | Hole depth (min.) | Rails per section |
|---|---|---|---|
| 4 ft | 6 ft (4×4) | 2 ft | 2 |
| 5 ft | 8 ft (4×4) | 2–3 ft | 2–3 |
| 6 ft | 8–9 ft (4×4) | 2–3 ft | 3 |
| 8 ft | 10–12 ft (4×4 or 6×6) | 3–4 ft | 3–4 |
- Depth: a common rule is to bury the post at least one third as deep as the fence is tall — about 2 feet for a 6 ft fence on 8 ft posts — and to go below the frost line in cold climates, which can mean 3 to 4 feet. Your local building department can tell you the frost depth.
- Diameter: about three times the post width: 10 to 12 inches for a 4×4, 16 to 18 inches for a 6×6.
- Spacing: 8 feet on center is standard because rails come in 8 ft lengths; windy sites and tall fences benefit from 6 feet.
- Drainage: put a few inches of gravel in the bottom of each hole and slope the concrete away from the post at the top so water sheds.
Picket counts for common fences
| Style | Picket | Gap | Pickets per 8 ft section |
|---|---|---|---|
| Privacy (side by side) | 1×6 (5.5 in) | 0 | 18 |
| Privacy (1×4) | 1×4 (3.5 in) | 0 | 28 |
| Picket fence | 1×4 (3.5 in) | 2.5 in | 16 |
| Shadowbox (both sides) | 1×6 (5.5 in) | about 3.5 in each side | about 22 in total |
Frequently asked questions
How many bags of concrete per fence post?
For a 4×4 post in a 10-inch hole 2 feet deep, about 1.5 bags of 80 lb concrete (or 2.5 bags of 50 lb). A 12-inch hole of the same depth takes about 2.3 bags of 80 lb.
How many posts do I need for 100 feet of fence?
At 8 ft spacing with no gates, 14 posts: 100 ÷ 8 = 12.5, rounded up to 13 sections, plus one post to close the last section. Each gate or corner adds one more.
Should fence posts be set in concrete or gravel?
Both work. Concrete is the most common choice for wood privacy fences; compacted gravel drains better and makes posts easier to replace. Either way, keep the bottom of the post on a gravel bed so it isn't sitting in water.
Do I need a permit for a fence?
Many towns require one, especially for fences over 6 ft or in front yards, and HOAs often have their own rules. Check before you buy materials — and call 811 to have utility lines marked before digging.
Sources
- Concrete volume per hole uses the QUIKRETE Concrete Mix yields (0.375 ft³ per 50 lb bag, 0.60 ft³ per 80 lb bag).
- Post depth and hole size follow common rules of thumb; your local frost depth and building code take priority. How we calculate.