Apply sound wood-post embedment and concrete footing methodology without relying on a single fabricated numeric rule of thumb.

Steps

1. Determine the local frost depth and set post embedment below the frost line where freeze/thaw heave is a risk, per the local building department's foundation frost-depth requirement.
2. Size embedment depth as a function of exposed fence height and expected lateral (wind) load rather than a single fixed depth that ignores height or soil type.
3. Account for site soil bearing capacity/soil class — looser or expansive soils generally warrant deeper embedment or a wider footing than firm native soil.
4. Confirm whether the local jurisdiction or project spec requires an engineered footing calculation (common for taller fences, solid/wind-sensitive panels, or gate posts) rather than a rule-of-thumb embedment.
5. Slope the concrete footing to drain away from the post and crown it above grade to reduce water-driven rot and frost-jacking at the post base.