Estimate buried post length and total post length from the height above grade and a bury fraction.
| Below grade | – |
| Total length | – |
Use this calculator to pick a post length before you dig. Enter the height above grade and the fraction of that height to bury (a common rule is one-third, so 0.33).
Below = above × fraction. Total = above + below. Height can be entered in metres (m) or feet (ft); buried and total lengths follow the same unit.
This is a rule of thumb. It does not check frost depth, soil, or wind, and it is not a foundation design.
Above grade: Exposed post height, in m or ft.
Bury fraction: Buried length as a fraction of the exposed height, for example 0.33 for one-third.
Below grade: Buried length.
Total length: Post length to buy.
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