Fence Picket Calculator

How to use the fence picket calculator

What this calculator does

This calculator turns the dimensions of a straight fence run into a practical material estimate. It calculates the number of pickets that fit across the run, rounds that count up to whole pieces, adds an optional spare allowance, estimates continuous rail footage, determines a post count from a maximum bay spacing, estimates total post stock, and subtracts the post displacement from cylindrical footing holes to estimate concrete. It is a planning tool, not a structural design or code-compliance determination. Gates, corners, slopes, wind exposure, frost depth, soil bearing, property boundaries, utility locations, and manufacturer instructions still need project-specific review.

When to use it

Use it while comparing picket widths and gaps, preparing a preliminary lumber order, checking how a tighter post layout affects the number of posts, or estimating concrete before digging. It is also useful when converting an existing US-customary sketch into metric dimensions because the measurement-system control converts the current values rather than merely changing their labels.

How to calculate

1. Start with the ready-to-use demonstration values. The first screen already contains a complete 100 ft example and a validated Excel workbook is immediately available.
2. Select Measurement system, then replace Fence length, Picket width, and Picket spacing with your measured values. Use decimal points, not decimal commas or scientific notation.
3. Set Extra pickets to the percentage you want for cuts, defects, and future repairs.
4. Open Posts, rails, and footing assumptions to enter the rail count, post spacing, height, post width, hole diameter, and footing depth.
5. Read Pickets to purchase first, then review the other result cards and the material schedule. Select Download Excel to export the current canonical values. Reset clears the demonstration and calculated state; Excel export remains unavailable until all required fields contain a complete valid plan again.

Input guide

Fence length is a required positive decimal measured in feet or meters; 100 ft is the demonstration value. A longer run increases every length-driven quantity. Do not enter separate runs as one length when corners, gates, or end conditions require extra posts. Picket width is the required actual face width in inches or centimeters; the example uses 3.5 in. Nominal board names may differ from actual dimensions. Picket spacing is the required clear gap in inches or centimeters; the example uses 1.5 in. A smaller gap increases the picket count, while a zero gap is valid. NIST documents the exact relationship between inches and metric length in its official SI length guidance.

Extra pickets is a required percentage from 0% through 100%; 10% is shown. It affects only the purchase count, not installed coverage. Rails per fence run is a required whole number from 1 through 10; two rails are typical for the example. Maximum post spacing is a required positive distance; 8 ft is shown. The calculator rounds the number of bays up, then adds one end post. Fence height is the required above-grade height; it combines with footing depth to estimate Post length. Post width, Post-hole diameter, and Footing depth are required positive values. The hole must be wider than the post diagonal so that the concrete annulus is physically meaningful. The example uses a 4 in square post, 12 in diameter hole, and 24 in depth. A post-setting guide may call for a hole roughly three times the post width and a depth related to above-ground height, but local conditions control; review the post-setting procedure and safety notes before work.

Output guide

Pickets to purchase is the whole installed count plus the selected extra percentage, rounded up. Installed pickets is the minimum whole-piece count from fence length divided by picket width plus spacing. Rails is total continuous rail length, before stock-length cutting loss. Posts is the number of bay endpoints for a straight run. Post length is fence height plus footing depth, not a recommended commercial stock size. Concrete volume is the net cylindrical hole volume after subtracting the embedded square post. 50 lb bags is a planning conversion using 0.375 ft³ per bag; always confirm the yield on the selected product. The Coverage per picket, Post bays, Concrete per post, and Total post stock cards expose intermediate values so you can audit the estimate. The schedule repeats these canonical values in purchase-oriented form.

Worked example

For the startup example, 100 ft equals 1,200 in. Each picket-and-gap module is 3.5 in + 1.5 in = 5 in, so 1,200 ÷ 5 = 240 installed pickets. Adding 10% produces 264 pickets to purchase. With an 8 ft maximum post spacing, 100 ÷ 8 = 12.5, which rounds up to 13 bays and therefore 14 posts. Two rail lines require 200 ft of rails. A 4 ft fence with a 24 in embedment requires 6 ft of post length, or 84 ft total for 14 posts. Subtracting the 4 in square post from each 12 in diameter, 24 in deep cylindrical hole gives about 1.35 ft³ per post and 18.88 ft³ total, equal to about 0.70 yd³ or 51 nominal 50 lb bags.