Frost Depth Calculator
By Region (US)
Look up typical frost depth by state/region
Modified Berggren Formula
Estimate frost depth from freezing degree days and soil properties
Formula
Stefan Equation: d = sqrt(48 × k × FDD / L) where k = thermal conductivity, FDD = freezing degree days, L = latent heat of soil
Frequently Asked Questions
What is frost depth and why does it matter?
Frost depth (frost line) is how deep the ground freezes in winter. Building foundations and footings must extend below the frost line to prevent frost heave, which can crack foundations and shift structures. Water pipes must also be buried below the frost line.
How deep is the frost line in my area?
Frost depth varies widely: 0 inches in southern Florida, 12-24 inches in the mid-South, 32-48 inches in the Midwest and Northeast, and 60+ inches in northern Minnesota and Alaska. Your local building code specifies the required footing depth.
Does snow cover affect frost depth?
Yes, snow acts as insulation. A consistent snow cover of 12+ inches can reduce frost penetration by 30-50%. Areas with bare ground during cold spells experience deeper frost penetration than those with snow cover.
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