A picket fence spacing calculator divides the gap between two posts into mathematically equal spaces between your pickets. Enter post span, picket width, and number of pickets to get exact fractional measurements in inches, millimeters, and a visual layout diagram.
Project Setup
Supports fractions: 3 1/2, 3-1/2, or 3.5
Results Breakdown
| Total Span | — |
| Element Width × Count | — |
| Remaining Gap Space | — |
| Number of Gaps | — |
| Exact Gap | — |
| Rounded Gap | — |
| Accumulated Error | — |
| Code Compliance | — |
Visual Span Diagram
Gap in All Formats
| Decimal Inches | — |
| Fractional Inches | — |
| Millimeters | — |
| Centimeters | — |
| Feet-Inches | — |
| Tape Measure Mark (nearest ¹⁄16″) | — |
Reverse Calculator
Enter your desired gap — we'll tell you how many elements fit.
📋 Cut List & Materials
| Elements Needed | — |
| Element Width | — |
| Total Linear Material | — |
| Spacer Jig Size | — |
Cut a scrap block to the spacer jig size for consistent spacing.
Recommended Gear
If you're building a fence or deck railing, having the right tools makes all the difference. We highly recommend a digital caliper for precise fractional measurements and a high-quality tape measure that won't flex over long spans.
Perfect Spacing Every Time
Whether you're building a picket fence, installing deck balusters, or putting up wall paneling, calculating the exact gap between elements is notoriously difficult. PicketPerfect eliminates the guesswork by instantly calculating the exact fractional gap required to evenly space your materials across any total span. With automatic rounding to the nearest 1/16" and dynamic visual diagrams, you can cut your spacer jigs with confidence. All calculations run locally in your browser for absolute privacy.
Frequently Asked Questions
How do you calculate equal spacing between fence pickets?
Measure the total span between end posts, subtract the combined width of all pickets, then divide the remaining space by the number of gaps (one more than the number of pickets if both ends have a gap, one fewer if the end pickets sit flush against both posts, or equal to the picket count if only one end has a gap). The result is your exact gap width.
What is the standard gap between fence pickets?
Most residential fencing uses 2.5" to 3.5" gaps between pickets. A residential guard under the IRC must not pass a 4" sphere (R312.1.3). Pool and spa barriers are stricter: ISPSC 305.2.2 sets the same 4" sphere limit, but where the barrier is built from horizontal and vertical members and the tops of the horizontal members are less than 45" apart, the horizontals must sit on the pool side and spacing between vertical members must not exceed 1 3/4" (ISPSC 305.2.5). The 4" spacing allowance applies only where the horizontal members are 45" or more apart (ISPSC 305.2.6). Always check your local code before building.
Why are my fence pickets uneven despite measuring carefully?
The most common cause is rounding errors that accumulate across many pickets. If you round each gap to the nearest 1/4", the error multiplied by 20+ gaps can shift the final picket by half an inch. Use fractional precision (1/16" or 1/32") and measure from a fixed end rather than picket-to-picket.