This page explains the measurement or planning assumption behind the result. When you need the project quantity itself, use Fence Picket Spacing Calculator.
Start with one clear panel opening
Measure from the inside face of one fixed panel boundary to the inside face of the other when that is the geometry the pickets must fill. Do not enter outside-to-outside post spacing unless you explicitly deduct the post widths first.
Check posts where the pickets actually land
Posts can be slightly out of plumb or rails can vary. Check the clear opening near the rail locations that control the picket plane and resolve a real field discrepancy before calculating a precise cosmetic gap.
Use actual picket face width
A nominal lumber description is not the installed face dimension. Measure representative finished material or use the exact product dimension, especially for vinyl/composite profiles or milled wood.
Treat gates, corners and grade steps as separate fields
A long project can contain several independent panels. Solving one averaged fence length can hide a visibly short closing gap in an individual bay. Calculate each distinct clear panel, then total material separately.
Decide the edge condition before solving
Some layouts place equal clear gaps at both panel edges; others place the first and last pickets flush to the boundaries. Those choices change the number of gaps in the formula, so record the intended condition before transferring marks.
Keep regulated barriers outside decorative assumptions
Pool barriers and other regulated applications can have opening, gate, climbability and structural requirements beyond cosmetic spacing. Use the applicable project requirements as inputs and do not treat a decorative example as approval.
Planning workflow
Define the two fixed boundaries
Mark the exact faces or lines that bound one picket field.
Measure the clear span
Record the span in one consistent plane and recheck obvious post lean or taper.
Measure actual picket width
Use the finished face that repeats across the panel.
Choose edge condition
Decide whether outside gaps are part of the pattern or the edge pickets land flush.
Solve and dry-mark
Use the calculator, mark from one datum, and verify the final edge before fastening material.
Example: 96 in clear bay
A clear 96 in bay with 3.5 in finished pickets is a valid input field. If the design includes equal gaps at both edges and the project-entered maximum gap is 3.5 in, the layout solver can choose a whole picket count and equalize the leftover space.
Reference table
| Measurement | Use | Do not substitute |
|---|---|---|
| Clear panel opening | inside boundary to inside boundary | overall fence length |
| Actual picket face | repeating visible width | nominal lumber name |
| Edge condition | equal outside gaps or flush edges | assumed gap count |
| Maximum gap | project-entered limit | generic decorative default |
Primary references for this planning guidance
These sources document the specific product or industry assumptions called out in this guide. Project specifications and the exact product instructions still take priority.
Supports: The installation guidance tells users to keep picket tops aligned with a guide and to use a spacer so decorative pickets maintain equal spacing rather than drifting across the run.
Boundary: The retailer guidance supports the field-layout workflow only. Product movement, fasteners, structure and permitted openings remain product/project/jurisdiction specific.
Supports: CPSC publishes configuration-specific opening, height, gate and climbability guidance for residential pool barriers and directs readers to local building/code authorities.
Boundary: This source is used to justify the calculator safety boundary, not to inject a universal fence-gap default. Local adoption, barrier configuration and complete project requirements must be verified separately.
Frequently asked questions
Should I measure between posts or across them?
Use the span that actually contains the pickets. For a typical bay that is the clear opening between the inside post faces; if your design references different boundaries, define and measure those consistently.
What if the opening is different at the top and bottom?
Resolve the field condition first. A precise equal-spacing number cannot make nonparallel boundaries disappear; decide the intended picket line and verify the result visually before fastening.
Can I measure the whole fence and divide it once?
Only when the whole run is genuinely one continuous layout field. Post-to-post bays, gates, corners and grade changes are usually better treated separately.
Planning note: Product coverage, yield, package size, installation instructions and project requirements take priority over generic examples. Verify the exact product and project before purchasing.