How do I calculate the number of ballusters between the posts on my new deck?

I need to find the number of ballusters and the spacing between them. I want an equal spacing between the ballusters. I also want the same spacing between the posts and the nearest balluster. I want to keep the spacing around 3 1/2 inches. It can not be over 4 inches. The distance between the posts ranges from 53 inches to 61 inches. The width of the ballusters in 1 1/4 inches.

Add 1 1/4" (the width of one balluster) to the space between two posts. For example, if you have a 61" distance between two posts, use 62 1/4". Then try dividing that by 3.5* (your desired spacing) and you get 17.5857. Since this is not a whole number, use 18 instead. Now divide the 61" distance by 18, which is 3.39, or about 3.4". Mark off the 61" space into 18 equal 3.4" parts. Note: since the marks indicate the centers of ballusters, the very FIRST mark from a post will be half the width of a balluster CLOSER to the post, in this case the very first mark will be 3.4"-.625" or just under 2.8". The last mark before you get to the post on the other end should also be just under 2.8" Each mark is the center of a balluster. If I figured this out right then all the spaces between the ballusters and the two end ballusters and the posts should be the same.

If you want a bigger space, try using 17 or 16 divided into the distance between posts instead of 18. Looks to me like 18 would place them too close together.

* In looking at this again I think since you want the space to be 3.5", you should probably add on 1 1/4 " so use 4 3/4" instead to allow for the thicknesses of the ballusters. I will get this worked out eventually. What I do sometimes is to make a computer model of the thing and just take measurements off that.


Will this work? I haven't a clue. But if you figure out what I tried to do you can always fix it.

You are asking a bit much, with the exact spacing at all points. after you get it all figured out, you will accidentally drill off center at least two of them, Add 1" (for the baluster) ( i know it's wider, but let's keep it simple and do-able) to the desired 4", making it 5". Divide the distance in inches by 5 and start drilling. When you are finished it will look right.

just keep marking it off till u get it like u want it -walmart has a nice project caculator for about 15.00