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Fence Picket Spacing Calculator

Fence spacing should be calculated from the clear opening between posts. Subtract the width of every picket and divide what remains by the number of gaps. A run with pickets at both ends has one fewer interior gap than pickets, while a run with equal end gaps has one more total gap.

Planning estimate only. Check measurements and real-world constraints before buying materials or making a commitment.

Last Updated: July 9, 2026

Calculate your scenario

Change any input. Results update immediately.

Clear opening between postsMeasure between the post faces.inActual picket widthUse actual, not nominal, width.inPicket countWhole pickets in this opening.Equal end gapsUse 2 for a gap at each post or 0 when pickets touch both ends.Minimum drainage gapUsed as a comparison threshold.in

Your results

Equal clear gap

0.646 in

Space between picket edges.

On-centre spacing

4.146 in

Picket width plus one clear gap.

Drainage check

Meets input minimum

Compared with 0.250 in.

How the calculation works

The calculator applies this relationship to the inputs above. Keep every measurement in the unit shown.

gap = (clear opening − picket count × picket width) ÷ gap count

Clear opening between posts96 in

Actual picket width3.5 in

Picket count23

Equal end gaps2

Minimum drainage gap0.25 in

Worked example

Use this example to check the calculator by hand before relying on a result.

Find total picket width

Actual picket width matters.

23 × 3.5 = 80.5 in

Find leftover width

This width becomes gaps.

96 − 80.5 = 15.5 in

Divide across 24 gaps

Two end gaps create one more gap than pickets.

15.5 ÷ 24 = 0.646 in

Assumptions behind the result

• Posts are plumb.
• Opening width is measured at the installation height.
• Pickets have equal finished width.
• Wood movement is not predicted.
• Local pool and guard rules are checked separately.

Mistakes that change the answer

• Including post width in the clear opening.
• Using picket count as gap count.
• Ignoring code limits for climbable or pool barriers.

Questions about fence picket spacing calculator

How many gaps are there between fence pickets?

With pickets touching both ends, there is one fewer gap than pickets. With equal end gaps, there is one more gap than pickets.

Do wood pickets need an expansion gap?

Usually yes, but the amount depends on moisture and material. Use the minimum-gap input as a planning check.

Can this confirm fence-code compliance?

No. Barrier and pool-fence rules vary. Check local requirements before choosing a gap.

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Calculator methods and editorial structure reviewed July 11, 2026. Results are estimates; verify regulated rates, eligibility rules, and professional decisions with the cited primary source.