A straight trellis needs support at both ends, even when the row length divides exactly into the desired span. Counting only the gaps between posts is a common way to leave an order one post short.
Use Trellis Materials Calculator to calculate spans from a maximum post spacing, add the two end positions and total wire across the entered horizontal levels. The worksheet includes an extra wire length per level for your tie allowance, then rounds the purchase into whole rolls.
Ten metres with three wire levels
For a 10 m row and maximum post spacing of 2.5 m, four spans are required. Four spans need five posts, including both ends. If redistributed evenly, the spacing remains 2.5 m.
With three wire levels and one extra metre per level, required wire is three multiplied by 11 m, or 33 m. A 50 m roll covers that quantity, so one whole roll is needed. At an example PKR 1,200 per roll, wire purchase cost is PKR 1,200.
That cost includes only the entered wire rolls. It does not include posts, anchors, fittings, labour or a structure whose support design has been checked.
Maximum spacing determines the number of spans
When row length does not divide exactly by the maximum spacing, the calculator rounds the span count up. It then reports equal spacing if the spans are redistributed across the whole row. That equal spacing will be no greater than the entered maximum.
The result assumes one straight line. Corners, independent sections and extra end supports need their own plan. Combining several unconnected rows into one long length would lose the end posts that each separate section requires.
The tie allowance is per horizontal wire level. It is not per post and is not a percentage of the total wire. Choose a value that matches how you intend to terminate the actual wires rather than accepting the example as a universal fitting allowance.
Materials arithmetic cannot certify strength
The tool does not calculate wind load, crop weight, post bending, anchor pullout or the strength of a wire product. It also does not decide what maximum spacing is structurally suitable. Those choices must be settled for the installation before the quantities become a useful order.
Use Garden Setup Budget Calculator to add the five posts and other components at their actual prices, keeping the wire cost on its own row. If planting along the trellis, Seedling Thinning Calculator can count spaced plant centres in a row, but its plant spacing is separate from support spacing. Plants do not determine the required strength merely by fitting between the posts.