Calculator inputs
Example data table
| Scenario | Total length | Excluded | Slope | Method | Input | Key output |
|---|---|---|---|---|---|---|
| Vegetable trellis line | 30 m | 0 m | 0% | Maximum spacing | 2.5 m max | 12 spans, 2.50 m spacing, 11 line posts |
| Garden fence with gate | 40 ft | 6 ft | 0% | Line post count | 10 line posts | 11 spans, 3.09 ft spacing, 12 total posts |
| Sloped orchard boundary | 60 m | 0 m | 8% | Maximum spacing | 3.0 m max, ground | 21 spans, 2.86 m spacing, 20 line posts |
Formula used
1) Effective horizontal length
Effective horizontal length = Total run length − Excluded length.
2) Slope adjustment (optional)
Ground length = Horizontal length × √(1 + (Slope% / 100)²). Use this only when measuring along the ground line.
3) Span count and spacing
If using maximum spacing:
Spans = ceil(Effective length used ÷ Maximum spacing), then Actual spacing = Effective length used ÷ Spans.
If using line post count:
Spans = Line posts + 1, then Actual spacing = Effective length used ÷ Spans.
If using span count:
Actual spacing = Effective length used ÷ Spans, and Line posts = Spans − 1.
4) Total posts
Total posts = 2 end posts + Line posts + Extra terminal posts. Extra terminals cover corners, braces, or special anchors you add.
How to use this calculator
- Measure your full run length from end to end.
- Subtract gate openings or clear zones as excluded length.
- Enter slope percent if the ground is sloped.
- Select whether you measure spacing on ground or plan.
- Choose a method: maximum spacing, line posts, or spans.
- Press Submit to see results above the form.
- Download CSV or PDF for your site notes.
Planning spacing for straight garden lines
Consistent post spacing keeps trellis wires, netting, and lightweight fences tensioned without sagging. This calculator starts with your total run length, then removes any gate opening or clear zone so the effective distance matches what you will actually support. Layout becomes predictable.
Choosing a practical spacing target
Spacing is a balance between strength, cost, and installation time. For vines and climbing crops, tighter spacing improves stiffness when plants add seasonal weight, especially after irrigation or rain. When you enter a maximum spacing, the tool selects the smallest whole number of spans that keeps the real spacing at or below your target. This helps protect against overstretched wire and reduces long-term retensioning.
Working with slope and measuring style
On sloped beds, the distance along the ground is longer than the horizontal plan length. If you measure tape on the ground line, select the slope option so spacing reflects the true path you will mark. The slope factor uses a square root relationship to convert plan length into ground length. For mild slopes the change is small, but across long runs it can shift several centimeters or inches.
Interpreting counts and positions
The calculator returns spans, line posts between ends, and total posts after adding any extra terminals for bracing, corners, or end anchors. It also lists post positions from the start point, which you can mark with paint, stakes, or a chalk line for fast layout. If your site has obstructions, keep the span count and redistribute positions locally while maintaining the same average spacing.
Using exports for field decisions
Download the CSV to share quantities with a supplier, estimate concrete or gravel needs, or compare layouts across multiple rows. Use the PDF when you need a printable record for site notes and crew handoff. When spacing is close to the limit, adjust the maximum spacing, switch to a fixed post count, or add one span to reduce the gap. Small changes prevent mid-project adjustments.
FAQs
1) What is a span in this calculator?
A span is the space between two adjacent posts. If you have 11 spans, you will have 12 post points along the run, including both ends.
2) Should I enter the gate width as excluded length?
Yes. Excluded length removes sections that do not need line posts, such as gates, driveway crossings, or planting gaps where no structure will be installed.
3) When should I measure along the ground line?
Choose ground line when your tape follows the slope on site. This makes the spacing match the distance you will mark in the field.
4) Why is my actual spacing smaller than my maximum?
The tool selects a whole number of spans. That rounding often makes the computed spacing slightly smaller than your maximum, which adds a safety margin.
5) How do extra terminal posts affect the layout?
Extra terminals increase total post count for braces or special anchors. They do not change the evenly spaced positions list, which is for the straight main run.
6) What spacing is typical for trellises?
Many lightweight trellises use 2–3 meters or 6–10 feet, depending on crop load and wire tension. Use your materials and local wind exposure to choose a limit.