How to Calculate Even Spacing

Many carpentry and craft applications require items to be spaced evenly across a given distance. Shaker style furniture makes extensive use of evenly spaced slats, while stair rails are often supported by evenly spaced balusters or spindles.

Outdoor projects, such as building a picket fence or planting a vegetable garden, also require these measurements. The trick to getting a perfectly even spacing in these applications is to measure each placement by its centre rather than its edge.

Measure the width of one baluster and the length of the rail onto which you are attaching balusters, slats or other items. Record these values.

Rail = 75 inches Baluster = 2 inches

Decide on an on-centre spacing for your items. Building codes will typically require 4 inches maximum on centre spacing. For the purposes of this example we will use a spacing of 3 inches.

Add the baluster width to both the rail length and the on-centre spacing.

75 + 3 = 78 inches for rail calculation 2 + 3 = 5 inches for baluster calculation

Calculate how many slats or balusters you need to fill the space evenly by dividing the rail calculation by the baluster calculation. Round down to the nearest whole number if necessary.

78/5 = 15.6

In this case you would round down to 15 balusters.

Subtract twice the number of balusters required from the rail calculation and divide the result by the number of required balusters, plus one.

78 - 30 = 48 48/16 = 3 inches

The on-centre spacing for the balusters or slats in this example is 3 inches.