Fence Calculator

This is an estimate, not professional advice. Check your inputs and verify the result against your plans and local building code before you build or order. See terms and disclaimer.

How this calculator works

Enter your dimensions and the result updates instantly. A waste allowance is included so you order slightly over rather than running short.

Worked example

A 100 ft privacy fence, 6 ft tall, with 3 ft entered below grade, 8 ft post spacing and 4x4 posts in 10 in holes. Inputs: Fence length 100 ft, Fence height 6 ft, Post depth below grade 3 ft, Concrete waste allowance 10 %, Post spacing 8 ft O.C., Post size 3.5 in, Post hole diameter 10 in, Picket width 5.5 in, Gap between pickets 0 in, Rails per section 3, Number of gates 0. Result: 219 (about 36 × 80 lb bags).

Materials for common fence lengths

Calculated for a 6 ft privacy fence on 8 ft post spacing with 4x4 posts in 10 in holes. Tap a length to load it in the calculator above.

Method & assumptions

A fence run is divided into sections between posts: the number of sections is your fence length divided by the entered maximum post spacing, rounded up, and the post count is one more so both ends are represented. The calculator does not choose a structurally adequate spacing.

Post depth is an input because soil, frost and local requirements control it. The QUIKRETE concrete calculator starts from a hole depth equal to one-half of the post height above ground, then tells the user to check local codes and frost depth. Enter the applicable depth; for a 6 ft fence that starting value is 3 ft. Concrete per hole is a cylinder minus the post volume over the entered depth. Post stock is the height above ground plus that depth, rounded up to the next available even length.

We apply the concrete waste allowance entered by the user before converting to bags and round every bag count up because you cannot buy a fraction of a bag. Set the allowance to zero when the measured hole volume or supplier quantity already covers irregular excavation. Picket count comes from the total run of fence that still needs pickets (a gate opening removes that section's pickets and rails but keeps its two posts) divided by the picket width plus any gap between boards.

The cited QUIKRETE guidance tells users to check local requirements and frost depth. This takeoff therefore leaves depth editable and does not turn its starting ratio into a universal installation rule.

Pro tips and common mistakes

• Check your local frost depth. QUIKRETE recommends a hole depth equal to half the exposed post height as general project guidance. In freezing climates the hole bottom also needs to sit below the local frost line, so confirm the locally required depth before ordering posts or concrete.
• Use the specified post schedule. Enter line, end, corner and gate post sizes from the project details; this calculator applies one entered size to the run.
• Measure each gate opening. The gate input removes whole fence sections. For openings with a different width, split the takeoff into runs or check the pickets and rails manually.
• Match the concrete product. The bag outputs use the exact yields cited for QUIKRETE No. 1101. Recalculate from the label when another mix is selected.

Frequently asked questions

Sources and references

These references and structured source records support the method and material data used on this page.

• Fence (Wikipedia)
• QUIKRETE Concrete Calculator: post-hole depth guidance
• QUIKRETE Fast-Setting Concrete Mix (product data)
• American Wood Council DCA 6: treated posts and exterior deck construction
• QUIKRETE Concrete Mix No. 1101 data sheet

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