How to Calculate the Distance in Railing Pickets

Contact your local building department and ask if there are any regulations pertaining to baluster spacing. There may be a maximum spacing distance. From this information, decide on an approximate spacing that you would like to have.

Measure the distance (in inches) that the picket fence will span.

Measure the width of your balusters.

Divide the length of your fence by the width of a baluster plus the spacing. As an example, if you are fencing a span of 120 inches, and both your baluster and estimated spacing are 4 inches, then you would divide 120 by 8, which means you will need 15 balusters.

Multiply the width of a baluster by the number of balusters. In the example given above, you would multiply 4 inches by 15 balusters, which results in 60 inches. This is the total width of all balusters.

Subtract the total baluster width from the length of the fence. In the example given above, you would take the 120 inches of fence length and subtract 60 inches of total baluster width. The remaining 60 inches is empty space.

Calculate the number of spaces. This will be the number of balusters, plus one, since you will have an extra space at the beginning of the run. In the example given above, you would have 16 spaces.

Calculate the exact spacing between balusters by dividing the total width of empty space on the fence by the total number of spaces. In the example given above, you would divide 60 inches by 16 spaces. This gives you an exact spacing of 3 3/4 inches between balusters.