Fence Post Calculator
Work out fence posts, sections, and concrete for a straight run of fence. Enter the total fence length and your post spacing to get post count, number of sections, and the recommended hole depth. Pair it with the post hole calculator to size the concrete per hole.
Fence Post Diagram
How the Formula Works
Calculate fence sections
Sections = ⌈Fence Length ÷ Post Spacing⌉ Always round up — a partial span still needs a full section and post
Calculate total posts
Posts = Sections + 1 + Gates A fence with N sections needs N+1 posts; each gate opening adds one extra post
Verify post hole depth
Hole Depth = max(entered depth, 24 in) Never less than 24 inches — check local frost depth for your region
Frequently Asked Questions
The formula is: Posts = (Fence Length ÷ Post Spacing) + 1. For a 100-foot fence with 8-foot spacing, that is (100 ÷ 8) + 1 = 13.5, rounded up to 14 posts. Add one extra post for each gate opening. Use the calculator above to get the exact count for your fence.
Standard post spacing is 8 feet (2.4 m) for wood privacy fences and picket fences. Chain-link fences typically use 10-foot (3 m) spacing. Rail fences often use 8–10 feet. Closer spacing (6 feet) adds strength in windy areas or for tall fences over 6 feet.
Post holes should be at least 1/3 of the total post length, with a minimum of 24 inches (610 mm). For a 6-foot fence using 8-foot posts, dig at least 2 feet deep (1/3 of 8 ft). In cold climates, always dig below the local frost line — which can be 36–48 inches in northern regions.
The rule of thumb is: Hole Depth = Total Post Length × 0.33. A 8-foot post needs a 2.6-foot (32-inch) hole. Always check your local frost line depth and use the greater of the two values. Posts set above the frost line will heave and lean over time.
Divide your total fence length by your desired section width to get the number of sections, then add 1 for the final end post. To space posts evenly, divide total length by the number of sections. For example, a 97-foot fence ideally divided into 8-foot sections needs 13 sections (97 ÷ 8 = 12.1, rounded up to 13), with posts at every 7.46 feet for even spacing.
Fence post holes should be 3 times the diameter of the post. For a standard 4×4 post (3.5 inches actual), dig a hole 10–12 inches wide. For a 6×6 post, use a 14–16 inch diameter hole. Wider holes allow more concrete to surround the post for better anchoring.
A typical fence post hole (12 inches diameter × 24 inches deep) needs about 0.2 cubic feet of concrete, or roughly one 50-lb bag of fast-setting concrete mix. Larger holes need proportionally more — use the concrete slab calculator to compute the exact volume for your hole dimensions.
Concrete provides the strongest, most stable anchor — recommended for privacy fences, tall fences, and any fence in high-wind areas. Gravel drainage is an alternative for areas with poor drainage or where post rot is a concern — it lets the post breathe and moisture drain. Many professionals use a gravel base (6 inches) with concrete on top for the best of both.