Free fence post calculator. Find how many posts, rails, pickets and concrete bags your fence needs - plus post depth and spacing guidance.
Your results will appear here.
Enter your values and press Calculate.
The calculator applies the industry-standard counting formulas: sections = fence length / post spacing (rounded up); posts = sections + 1 (both ends need a post) plus corners and 2 jamb posts per gate; rails = sections × 2-3 depending on height; pickets = run length in inches / board width plus 10% waste; concrete = 1.5 bags of 80-lb mix per post; hole depth = one-third of fence height, minimum 24 inches. Results are planning estimates - check local frost depth and permit rules before digging.
Fencing is a counting problem with one trap in it: posts are always one more than sections, because both ends of the run need one. The calculator applies the consensus formulas:
Sections = ceil(fence length / post spacing) Posts = sections + 1 + corners + (2 × gates) Rails = sections × rails per section (2 under 5 ft, 3 at 5 ft and above) Pickets = ceil(length in inches / picket width), plus 10% waste Concrete = 1.5 bags of 80-lb mix per post
Worked example - 100 ft fence, 8 ft spacing, 6 ft high, no corners or gates: sections = ceil(100/8) = 13, posts = 14, rails = 13 × 3 = 39, pickets = ceil(1200/5.5) = 219 (+10% = 241 to buy), concrete = 14 × 1.5 = 21 bags of 80-lb mix.
Enter your total fence length in feet, post spacing (8 ft is the standard for wood privacy fences, 6 ft in windy areas, 10 ft for chain link), fence height, number of corners, number of gates, and picket width if you are building board-by-board.
The calculator returns posts, sections, rails, pickets (with 10% waste included), 80-lb concrete bags, and the recommended hole depth. Measure each straight run separately and add them - never eyeball a curve or angle as one measurement.
Post spacing is set by what the fence hangs on. Wood privacy and picket fences: 6-8 ft on center. Vinyl and pre-built panels: the panel width (usually 6 or 8 ft) sets the spacing - never exceed it, since posts must support both ends of every panel. Chain link: line posts every 10 ft, since the mesh carries tension between them.
Tighter spacing is stronger but not free: dropping from 8 ft to 6 ft on a 200 ft run adds about 9 posts and 27 rails - roughly 33% more posts and concrete. Use 6 ft spacing in high-wind areas or for heavy panels; 8 ft is fine for a standard 6 ft privacy fence on flat ground.
Bury about one-third of the post's total length, and never less than 24 inches: a 6 ft fence needs holes 24 in deep with 8 ft posts; an 8 ft fence needs 36 in holes with 12 ft posts.
In cold climates the frost line overrules everything - dig below it or frost heave will push shallow posts up over a few winters. Frost depth is near 0 in across Florida and southern California, 24-42 in through the Midwest, and past 48 in in the northern tier and New England. Your county building department publishes the exact number.
Make the hole about 3x the post width (10-12 in for a 4x4), add 6 in of gravel at the bottom for drainage, and set corner, end and gate posts deeper in wider footings - they carry far more lateral load than line posts.
Concrete per post depends on hole size. For the standard 4x4 post in a 10-inch diameter, 24-inch deep hole: about 0.69 cubic feet, or roughly 1.5 bags of 80-lb mix (one 80-lb bag yields ~0.6 cu ft). The calculator uses 1.5 bags per post and rounds up.
Quick reference (80-lb bags per hole): 4x4 in 8x24 in hole ~0.7 bags; 10x24 in ~1.2; 10x30 in ~1.5; 12x36 in ~2.9. Corner and gate posts in wider, deeper holes take 2-3 bags each.
Let concrete cure 24-48 hours (whatever the bag says) before hanging rails or gates. One caution from the field: a wood post buried directly in concrete tends to rot at the concrete line first - a galvanized steel post sleeve sidesteps the most common failure point of a wood fence.
Rails: most privacy fences use 2 horizontal rails per section under 5 ft tall, and 3 (top, middle, bottom) at 6 ft and above, running between each pair of posts.
Pickets: for standard 5.5-inch boards butted tight, a 100 ft fence needs about 219 pickets - roughly one per 5.5 inches of run. The calculator adds 10% for cuts, splits and bad boards (order 241). With a gap between boards, divide by (board width + gap) instead.
Pre-built panels simplify the math: panels = ceil(length / panel width), one post at every joint. Panels install faster but cost more per foot and do not flex for odd-length runs.
Corners: add one post per corner - and upsize them. A 5x5 or 6x6 corner post in a wider, deeper footing handles the lateral load where the fence changes direction.
Gates: each gate opening needs 2 jamb posts (one per side), set deeper like corners. A standard walk gate is 3-4 ft wide; a single drive gate 10-12 ft; a double drive gate 20-24 ft. Confirm the opening against your gate hardware spec - hinges shave a couple of inches off the nominal size.
Slopes: break the run into straight segments at every direction change and measure along a string line, not along the ground - measuring along the slope overstates materials. Stepped panels stair-step down the slope (simpler, cheaper); racked panels follow the grade continuously (needs slope-rated panels).
Before you dig: call 811 (US) at least 3 days ahead - it is free, and hitting a utility line turns a $200 project day into a very expensive one. Many municipalities require a permit for fences over 6 ft or on a property line ($50-$300 typical). Check HOA rules too - height and style restrictions are common.
DIY vs pro: a 100 ft straight wood privacy run is a weekend for two people with a post-hole digger or rented auger; a pro crew does it in 1-2 days. DIY saves roughly 30-50% (labor is up to half the installed cost); it saves least on chain link, which is already fast to install professionally. Get two or three local quotes before setting a budget - region, height, gates and site conditions move the number a lot.
Sections = ceil(length / spacing), posts = sections + 1. At 8 ft spacing a straight run needs 14 posts for 100 ft, 20 for 150 ft, 26 for 200 ft. Add one per corner and two per gate opening. Enter your numbers above for the exact count.
6-8 ft on center for wood privacy and picket fences (8 ft is the standard), the panel width for vinyl and pre-built panels, and 10 ft for chain link line posts. Use 6 ft spacing in high-wind areas.
About one-third of the post's total length, minimum 24 inches - so a 6 ft fence needs 24-inch-deep holes. In cold climates, dig below the local frost line regardless, or frost heave will push posts up over time.
About 1.5 bags of 80-lb mix per standard 4x4 post (10-inch diameter, 24-inch deep hole). Corner and gate posts in wider holes need 2-3 bags each. The calculator above totals it and rounds up.
About 219 for a 100 ft run with 5.5-inch boards butted tight (length in inches / board width), plus 10% for cuts and waste - order 241. The calculator includes the waste allowance automatically.
A 100 ft wood privacy fence runs roughly $1,500-$3,500 installed ($15-$35/ft); materials alone are about half that. DIY saves the labor share - up to half the total on wood privacy. Always confirm against two or three local quotes.
Often yes - many municipalities require one for fences over 6 ft or on a property line, typically $50-$300. And call 811 before you dig anywhere in the US; the utility locate is free and legally required in most states.
One foot measured along the fence line, regardless of height. It is the standard unit contractors use for pricing and materials - so a '100 linear foot' fence is simply 100 feet long.
Fence rails are the horizontal boards that pickets attach to. A rail fence calculator rule of thumb: most wood fences need 2 rails per section for fences up to 6 ft tall, and 3 rails for 8 ft fences. Space rails evenly, top, middle and bottom, and use pressure-treated 2x4 lumber. Metal and vinyl fences use prefabricated rail brackets instead.