Count the empty spaces first
In this planner a bay is the clear space between two battens. If you want six bays with a batten at both ends, you need seven battens. Counting bays as battens makes the layout one piece short and changes every gap. This tool covers decorative vertical battens over an existing surface, not exterior siding systems or structural installation.
Subtract the width of the material
Clear gap = [wall width − (bays + 1) × batten face width] ÷ bays. With a 300 cm wall, six bays and a 4 cm visible batten width, the timber occupies 7 × 4 = 28 cm. The gaps share the remaining 272 cm, giving 45.33 cm per gap. Use the actual visible width of your material rather than relying only on a nominal product label.
Centre spacing is a different number
The distance from one batten centre to the next is the clear gap plus one full batten width. In the example, it is 49.33 cm. The first left edge is at zero, the second at 49.33 cm and the third at 98.67 cm. Measuring all marks from the same end reduces the chance of accumulating small rounding errors by repeatedly measuring the last gap.
Check the far edge
The final batten should end at the far edge of the wall. In the example the last left edge is 296 cm and its 4 cm width finishes at 300 cm. The position table gives the left edge and centre for every piece. It displays rounded measurements, so keep the complete plan and check the last position rather than adding rounded gaps together.
Understand what the material total includes
The vertical total is batten quantity multiplied by the height you enter. Seven pieces at 120 cm total 840 cm, or 8.4 m. Top rails, bottom rails, backing boards, kerf, fixings and spare stock are not included. This planner assumes a simple unobstructed rectangle. Use a separate layout for a wall with a door or window, and verify the physical installation independently.