Picket spacing calculator for stairs.
This calculator uses Javascript.

Baniser on stairs
This calculator will enable you find the visual gap that results from putting some number of pickets evenly between two posts that are at different heights.
It will then produce a marking list that can be measured onto the sloping rails and used to place the pickets.
Normally you would try different numbers of pickets to a get a gap that best matches the gaps in other parts of the structure.  

To produce a list of  spacings enter requested information in mm.
Span....(S)
Number(n)
Width...(w)
Run.....(R)