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`oC = "L" /( "n" -1)`

Enter a value for all fields

The **On Center Spacing** calculator computes the even spacing between a number (**n**) of objects (e.g. posts, studs, joists, rafters, trusses, lights, rebars) over a specific length (**L**).

**INSTRUCTIONS:** Choose units and enter the following:

- (
**L**) Length over which the objects are spread (e.g., a fence that is 240 feet long) - (
**n**) Number of objects being spread over the distance (e.g., 31 posts)

**On Center Spacing (oC):** The calculator returns the even separation in inches. However, this can be automatically converted to other length units (e.g. feet or meters) via the pull down menu.

The on center calculation is fairly easy. However, people typically fail to account for the first object. So, if you want to spread 4 posts (n) out to create a fence 24 feet long (L), you can not spread them out where spread = 24 ft/4. This forgets that the first post is at position zero. You a have to reduce the number of posts by one for the first post. In this case, the calculation would be 24 ft/3 (3 = n-1), which 8 ft separation. The formula for on center spacing is

oC = L / (n-1)

where:

- oC = on center spacing
- L = length
- n = number of objects

Many applications of spacing can be seen in life. Three common spacing examples are fences, floor joist and the spacing of studs.

Spacing of joists

Spacing of studs

Spacing of rebar