Enter values and press the "Calculate" button to calculate the factors. Tolerance allows you to see whether a small violation in spindle spacing would save a spindle. Units are assumed to be in inches, but could be in any units if the decimal reulsts box is checked.
Fractions must be entered as decimal numbers (i.e. 3/4" = 0.75)
A nice calculator with images showing the calculations is available here: www.decks.com/calculators/baluster-spacing. The decks.com calculator can also calculate steps, where the spacing along the railing is increased by the cosine of the stair angle.