How it works
The calculator lays the fence out as post, panel, post, panel along the line, leaves room for each gate and its extra post, and rounds up to whole panels.
Post spacing on center = Panel opening + Post width
Open fence: Panels = ⌈ (Length − Post width − Gates × (Post width + Gate width)) ÷ Spacing ⌉, Posts = Panels + 1 + Gates
Closed fence: Panels = ⌈ (Length − Gates × (Post width + Gate width)) ÷ Spacing ⌉, Posts = Panels + Gates
Post caps = Posts; Brackets = Panels × Brackets per panel; Screws = Brackets × Screws per bracket
⌈ ⌉ means rounding up to a whole panel; the leftover, less one post width, is the width of the last cut panel. The rule “one post per panel and one to complete the fence run” is from UFP’s panel instructions, and the on-center spacing of panel width plus post width from Freedom’s vinyl fence guide. A 100 ft fence with a 4 ft gate, 67 in openings and 5 in posts: (1,200 − 5 − 53) ÷ 72 = 15.86 → 16 panels, 18 posts, the last panel cut to 57 in. Units are converted internally, so feet, inches and meters can be mixed.
Worked example
Inputs
- Fence length
- 100 ft
- Fence shape
- Open – the fence has two ends
- Gates
- 1
- Gate opening width
- 4 ft
- Panel opening
- 67 in
- Post width
- 5 in
- Brackets per panel
- 4
- Screws per bracket
- 4
Result
- Fence panels
- 16
- Posts
- 18
- Of which gate posts
- 2
- Post caps
- 18
- Brackets
- 64
- Bracket screws
- 256
- Post spacing on center
- 72 in (6 ft)
- Last panel cut to
- 57 in (4.75 ft)
Common mistakes
- Spacing posts by the nominal panel width. An "8 ft" or "6 ft" panel is rarely that wide – use the opening from the maker’s instructions and add one post width for the on-center spacing.
- Forgetting the extra post at each gate. A gate opening has a post on both sides, so every gate in a fence line adds one post.
- Setting all the posts before the panels. Makers have you set one post, hang a panel and set the next, so the opening stays right.
- Counting brackets per post instead of per panel. Each panel needs its own brackets at both ends of every rail.
- Measuring the fence from post center to post center. This calculator wants the full length from the outside of the end posts.
Assumptions and limits
- Posts and panels alternate along the line; an open fence starts and ends with a post, and each gate is an opening between two posts.
- All panels and gates of one kind are the same width. The last bay takes a cut panel when the length does not divide evenly.
- Corner posts are shared by the stretches they join, so corners add no posts – but each stretch is rounded to whole panels on its own when you build it.
- One post cap per post. Bracket and screw counts are what you enter per panel and per bracket; post sizes, depths and footings follow the maker and your local code – this is a quantity estimate, not a structural design.
Frequently asked questions
How many fence panels do I need for 100 feet?
It depends on the real panel opening and post width. With 67 in openings and 5 in posts, posts are 72 in on center, so 100 ft with one 4 ft gate takes 15.9 → 16 panels and 18 posts. Without a gate, 1,195 ÷ 72 = 16.6 → 17 panels and 18 posts.
How many posts do I need for fence panels?
One per panel plus one to finish the run, as UFP’s instructions put it, plus one for each gate. A closed fence that runs all the way round needs one post fewer.
How far apart are posts for 6 ft or 8 ft fence panels?
The panel opening plus one post width, on center. Freedom’s vinyl fence guide says to measure the panel width plus the post width for the center-to-center distance; UFP’s 6x6 panel needs 67 in between posts, so with 5 in posts that is 72 in on center.
How many brackets does a fence panel need?
Usually one at each end of every rail. A two-rail panel takes four brackets, as in UFP’s 6x6 kit; a three-rail panel takes six. Panels that slide into routed posts need none.
Panel fence or picket fence – which calculator should I use?
Use this one for ready-made panels hung between posts. For a fence built picket by picket on rails, the fence picket calculator counts the boards; the fence post calculator counts posts by a maximum spacing.
Sources
- 6x6 Board-on-Board Privacy Panel Bundle – Assembly and Installation Instructions (10550_3/19) — Universal Forest Products (UFP), hosted by Lowe’s. Kit: 2 rails, 7 pickets, "4 - mounting brackets with fasteners"; actual size 68.5 in h × 66.875 in w; "Inside-to-inside post distance is 67"" (opening default 67 in); fence posts "One per panel and one to complete fence run"; screws "four per bracket"; "Install a post cap on each post".
- Ready-to-Assemble Privacy Vinyl Fence Installation Instructions (web rev. 08.23) — Freedom Outdoor Living, hosted by Lowe’s. "Measure the width of the fence panel (X) plus the width of the post (Y). This is the common center-to-center measurement (unless there is a cut-down panel)"; hole diameters "10" for 5" x 5" post, 8" for 4" x 4" post" (post width default 5 in).
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.
Method reviewed November 6, 2026