Post Foundations
WHAT SIZE FOUNDATION HOLE SHOULD I DIG?
Digging the correct size hole
Many installers, both good and bad, have a preconceived idea on how big the foundations for a sign post should be.
There is no substitute for experience, but the table below is a good starting point for those of us with little, or no experience at all.

Please note that this is a guide only, if in doubt please contact your local civil engineering department for more information.