Use this free fence picket calculator to estimate one straight, single-sided run of vertical boards, posts and rail pieces. Enter the boarded run length, planned maximum post spacing and actual picket width. Gates, turns and double-sided layouts need separate counts.
How it works
Sections are the fence length divided by the post spacing, rounded up. A straight fence needs one more post than sections. Each section gets two or three rails. For N pickets there are N – 1 gaps. Pickets = round up ((boarded length in inches + gap) / (actual width + gap)), then add the chosen extra and round up. The post estimate treats the spacing input as a maximum for one straight run; final section lengths need a layout.
Worked example
A 100 foot fence with posts every 8 feet: 100 / 8 = 12.5, so 13 sections and 14 posts. With 3 rails per section that is 39 rails. With 5.5 inch pickets and a 1/4 inch gap: (1,200 + 0.25) / 5.75 = 208.7391, so 209 pickets, plus 10% = 230.
What this does not cover
- Gates, which need extra posts and hardware.
- Corners and end posts, which can change the post count.
- Sloped ground, which changes how pickets and rails are cut.
- Local height and permit rules. Check with your city or HOA before you build.
To set the posts in concrete, use the fence post concrete calculator.
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What you’ll need
A plain checklist. Needs vary by project, so follow the instructions on your materials.
- Post hole digger or auger – for post holes.
- Level and string line – keeps posts and the fence line straight.
- Fasteners made for outdoor use – galvanized or coated, per the lumber maker.
- Drill, saw and hammer – for rails and pickets.
- Tape measure – for spacing.
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Estimates only. Confirm quantities and product details with your supplier before you order.
Guide: How many fence pickets do I need
What the fence calculator counts
- Pickets: one single-sided, non-overlapping run. The allowance is added only here.
- Posts: round up (run length / maximum spacing), then add one end post.
- Rails: sections x selected rails per section. These are rail pieces assigned to sections, not an optimized number of stock boards.
The input is not a complete fence design. A 100-foot run at a maximum 8-foot spacing needs 13 sections in this model. It could have twelve 8-foot sections and one 4-foot section, or thirteen roughly equal sections. That decision changes cuts and joint positions. Gate locations and corner posts must be laid out first. Longer rails can span several posts; Lowe’s installation guide discusses alternating rail joints on different posts.1
Actual picket width is what matters
Check the actual face width on the product or measure it. A Lowe’s Severe Weather picket is named 6 inches wide but lists actual width as 5.5 inches. That is one product example, not a guarantee about every 6-inch picket.2 Using 6 instead of 5.5 in a tight 100-foot run would estimate 200 base pickets instead of 219, a 19-picket shortfall before extra.
Free picket chart for a straight 100-foot run
Our calculations use actual width, N – 1 gaps and a 10 percent example allowance. Pickets cover the stated continuous run; posts are not deducted. All rows assume one side only and do not plan an overlapping pattern.
| Actual picket width | Gap | Base pickets | With 10% extra |
|---|---|---|---|
| 3.5 in | 0 in | 343 | 378 |
| 3.5 in | 0.25 in | 321 | 354 |
| 5.5 in | 0 in | 219 | 241 |
| 5.5 in | 0.25 in | 209 | 230 |
| 7.25 in | 0 in | 166 | 183 |
| 7.25 in | 0.25 in | 161 | 178 |
Two more checked examples
48-foot tight fence, 5.5-inch pickets, 8-foot maximum spacing: 48 / 8 = 6 sections, 7 posts. At three rails per section, count 18 rail pieces. Pickets: 576 / 5.5 = 104.7273, round to 105. Add 10 percent: 115.5, round to 116 pickets. Rails and posts have no extra allowance in this result.
30-foot run, 3.5-inch pickets, 2-inch example gap, 6-foot maximum spacing: five sections, six posts and ten rail pieces at two per section. Pickets: (360 + 2) / (3.5 + 2) = 65.8182, round to 66. At 10 percent extra, 72.6 rounds to 73. The gap is an arithmetic example, not a safety or code recommendation.
Solid, spaced and shadowbox fences are different
This tool is for one line of vertical pickets on one side. A shadowbox fence alternates boards on opposite sides and needs a separate overlap layout. Do not assume its count equals a solid fence or simply double the output. A board-on-board privacy layout overlaps faces, so effective coverage is narrower than actual board width. A horizontal-board fence is a different takeoff too. Use our fence picket quantity guide for the basic counting method.
Posts and rails need their own plan
The two- or three-rail choice is an input, not a structural recommendation. Lowe’s says a stringer is typically needed for each 2 feet of post height and explains that rails follow the ground contour. Use the design and material instructions for your fence rather than treating that rule or this dropdown as approval. Wind exposure, height, soil, gates and local requirements matter.1
Separate turns into straight runs, then reconcile shared posts so you do not count the same corner twice. An open gate changes both the boarded length and the post layout. Subtracting its width from total fence length alone does not establish the right post count. See our post spacing guide and post concrete guide; confirm your property boundary, utility marking and local rules before digging.
Turn fence quantities into a budget
Our quote-comparison checklist: price the planned fence, not just a calculator total. This tool counts one straight, single-sided run. It does not place gates, reconcile shared corner posts or turn rail pieces into a stock-board cutting list.
- Give each quote the same layout. Record the straight runs, fence height, gates, corners and selected pattern. Keep the boarded length distinct from the full boundary length. Ask the installer to confirm post locations before using the calculator’s post count.
- Name the materials. List the actual picket width, chosen gap, wood or other material, post specifications and finish. A nominal board name alone is not a complete product specification.
- Convert rails to a purchase list. Ask for the required rail-piece lengths, stock-board lengths, joints and cut allowance. Do not price the section rail count as a stock-board count without that check.
- Separate extras and included work. Ask which gates, hardware, post concrete, fasteners, finishing, removal, disposal and installation work are included. Keep delivery, tax and any access charges visible.
- Check terms and changes. Ask about stock, delivery, return rules and how extra work will be approved and charged. Record who handles boundary confirmation, utility marking and any required approvals.
Use the fence cost guide for its named cost references and our project planning and quote checklist to track scope and exclusions. Do not add material costs again to an installed quote that already includes them. These are our comparison prompts, not a fence design or promises about supplier terms.
Frequently asked questions
Does the waste percentage add spare posts and rails?
No. It applies only to the picket count. Posts and rails remain the basic straight-run layout count. Add material for gates, special posts, cuts and rejected stock separately after you have a cutting list.
Why does the formula add one gap to the run length?
A row of 10 pickets has 9 gaps between them. Covered length is N x width + (N – 1) x gap. Solving gives (target length + gap) / (width + gap). The formula does not add an extra gap at the far end.
Can I treat the rail count as how many 8-foot boards to buy?
Only if the planned sections, joints and stock lengths actually support that cut list. Longer boards can supply more than one short rail piece; required lengths and cut loss may make a nominal board too short for another piece. The calculator does not optimize that purchasing list.
Sources
- Lowe’s: Wood Fence Tips, Installing Posts, Rails and Pickets (retailer installation guidance on stringers, joints and layout; read October 7, 2026)
- Lowe’s: Severe Weather dog-ear picket (one product’s nominal 6-inch name and actual 5.5-inch width; no price or availability claim; read October 7, 2026)