There are basically 4 steps to finding your stair calculations.
Step 1:  Typically the balusters at each end, nearest the posts and or walls, are in 3”.  You may want to adjust this later to make the spaces more even but this is a good starting point.  So you begin by measuring your knee wall length between posts or whatever terminations you might have.  Let’s say the measurement is 144 ½” and subtracting 6”. (3” from each end for the first and last baluster)

Step 2:  Determine the approximate layout by adding the thickness of your baluster at its narrowest point to the constant of 4 ½”.  Assuming a 3/4” narrowest-point baluster the formula and result is as follows: 0.75 + 4.5 = 5.25 or 5 ¼”

Step 3:  Divide the total knee wall length less 6” by the approximate baluster spacing, figured in step 2, then round up.  Using our example that is 138.5 ÷ 5.25 = 26.38 or 27 spaces.

Step 4:  Now, to get the exact spacing divide the length 138.5 by 27 to get the final measurement of 5.13 or 5 1/8”.

Now we have all of the information we just need to put it all together.  We have 27 spaces between 26 balusters plus the additional 2 that start 3” away from the termination at each end and are spaced 5 1/8” apart.  Thus our stair calculations brings us to the conclusion we will need 28 balusters.

This may seem a little complicated so please don’t hesitate to call if you have any questions regarding design, layout, installation or any of our products and services.