Fence Calculator
Plan a wood picket or privacy fence: enter the total length, height and post spacing to get posts, rails, pickets and the bags of concrete to set the posts, plus how deep to dig.
How to use the fence calculator
- Measure every side you're fencing and add them up, including gate openings. Enter the fence height and post spacing (6–8 ft is common).
- Add a post for each corner and each place the fence ends and restarts under Corners and extra ends.
- Enter the number and width of gates. Their width is taken out of the picket count and each gate adds a post.
- Set the picket width and gap (0 for a privacy fence). Leave rails per section empty for the automatic rule: 2 rails up to 4 ft high, 3 above.
- Check the post size, hole diameter and depth, then enter your prices under Cost estimate.
How the fence calculator counts materials
- Sections = fence length (without gates) ÷ post spacing, rounded up
- Posts = sections + 1, plus 1 for each corner or extra end, plus 1 for each gate
- Rails = sections × rails per section (2 for fences up to 4 ft, 3 for taller fences, unless you set your own)
- Pickets = fence length in inches ÷ (picket width + gap), rounded up, plus a waste allowance
- Concrete per post = the volume of the hole (π × (diameter ÷ 24)² × depth) minus the part filled by the post
The concrete is then converted to bags: about 0.60 ft³ per 80 lb bag, 0.45 ft³ per 60 lb bag and 0.30 ft³ per 40 lb bag (Quikrete data sheet).
Worked example: 100 ft of 6 ft fence, posts every 8 ft
This is the fence loaded above: one straight run of 1×6 pickets (5.5 in wide) with ½ in gaps on 4×4 posts.
- Sections: 100 ÷ 8 = 12.5, rounded up to 13.
- Posts: 13 + 1 = 14.
- Rails: 13 sections × 3 rails = 39 (3 per section because the fence is over 4 ft).
- Pickets: 1,200 in ÷ 6 in = 200, plus 5% = 210.
- Concrete: each 10 in hole, 36 in deep, holds π × (10 ÷ 24)² × 3 = 1.64 ft³; the 4×4 takes up 0.26 ft³, leaving 1.38 ft³ per post. For 14 posts plus 10% that is 21.3 ft³, or 36 bags of 80 lb mix (about 2.5 bags per post).
- Posts: a 36 in hole under a 6 ft fence needs posts 9 ft long, so you would buy 10 ft posts and trim them.
How deep should fence posts be?
Quikrete's instructions for setting fence posts say to dig the hole about 3 times the post's width and one third of the post's total length deep, and to put about 6 in of dry concrete mix at the bottom before setting the post. For a 6 ft fence, one third of a 9 ft post is 36 in. In cold climates, posts should also go below the frost line so they don't heave. Check your local code: some towns and HOAs set post depth, fence height and how close you can build to the property line.
Posts, rails and pickets by fence length
| Fence length | Posts at 8 ft | Posts at 6 ft | Rails at 8 ft (3/section) | Pickets (5.5 in, no gap) |
|---|---|---|---|---|
| 50 ft | 8 | 10 | 21 | 110 |
| 75 ft | 11 | 14 | 30 | 164 |
| 100 ft | 14 | 18 | 39 | 219 |
| 150 ft | 20 | 26 | 57 | 328 |
| 200 ft | 26 | 35 | 75 | 437 |
| 300 ft | 39 | 51 | 114 | 655 |
One straight run with no gates or corners. Add a post for each corner and each gate. Pickets have no waste added.
Fence planning tips
- Call 811 before you dig. It's the free US call-before-you-dig number; utilities will mark buried lines.
- Confirm the property line. Use your survey or plat. Many owners set the fence slightly inside the line to avoid disputes.
- Match the spacing to your panels. If you are using pre-built 8 ft panels, the post spacing must be 8 ft on center; the calculator's section count is then your panel count.
- Gates need stronger posts. Gate posts carry more load; many builders use a larger post or a deeper hole on each side of a gate.
- Slopes change the count. On a slope, measure along the ground for rails and stepped panels, and expect a few extra pickets for trimming.
Frequently asked questions
How many fence posts do I need for 100 feet?
With posts every 8 ft, a straight 100 ft fence has 13 sections and 14 posts. With 6 ft spacing it has 17 sections and 18 posts. Add one post for each corner and each gate.
How many bags of concrete do I need per fence post?
For a 4×4 post in a 10 in hole 3 ft deep, about 1.4 ft³ of concrete: 2.3 bags of 80 lb mix, so 3 bags if you mix each hole separately. A 6×6 in a 16 in hole needs considerably more; enter your sizes above.
How deep should a fence post hole be?
Quikrete recommends about one third of the post's total length (36 in for a 6 ft fence on 9 ft posts) and at least below the frost line where the ground freezes. Your local code may set its own minimum.
How many pickets do I need for a fence?
Divide the fence length in inches by the picket width plus the gap. For 100 ft of 5.5 in pickets with ½ in gaps: 1,200 ÷ 6 = 200 pickets, plus about 5% for splits and cuts.
How far apart should fence posts be?
6–8 ft on center is typical for wood fences. Closer spacing makes a stiffer fence and is common for taller privacy fences and windy sites; panel fences must match the panel width.
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