⛏️ Fence Post Depth Calculator
Find out how deep to dig your fence post holes based on your fence height, local frost line, and post size.
What this calculator does
The fence post depth calculator estimates how deep to dig each post hole so your fence stays stable and, in cold climates, below the frost line.
The formula
A common rule of thumb is to bury about one-third of the post’s total length in the ground. This calculator compares that one-third rule against a frost-line rule (going 6 inches below your local frost depth, if you have freezing winters) and a general minimum of 24 inches, then uses whichever is deepest. Hole diameter is estimated at roughly three times the post’s width to leave room for concrete or tamped backfill on all sides.
Local frost depths and soil conditions vary widely — check with your local building department or extension office for exact frost-line requirements in your area before digging.