Hammer CalculatorCalculators / Concrete / Footing Depth Calculator
Concrete Footing Depth Calculator
Determine the minimum footing depth, recommended width, and thickness based on your local frost line, soil type, and structure loads.
Footing Depth Calculator
Frost depth varies by jurisdiction. Check your local building code or contact your building department for the exact frost line depth in your area.
Footing Section
Hover for details • cross-section view
Minimum Depth
42″
3.5 ft (frost line + 6″)
Recommended Width
16″
Based on average soil & 1-story
Min. Thickness
6″
Projection rule (min 6″)
Soil Bearing Capacity
2,000 psf
average soil rating
Footing sizing summaryFor a 1-story residential structure on average soil with a 36″ frost line: dig to at least 42″ deep, use a footing at least 16″ wide and 6″ thick. Always verify with your local building code.
Why footings must go below the frost lineWhen water in the soil freezes, it expands and pushes upward (frost heave). A footing placed above the frost line can shift and crack the structure above. Building codes require footings to sit at least 6″ below the local frost depth to prevent this movement.
This calculator provides general guidance based on standard residential building practices. Footing requirements vary by local building code, actual soil conditions, and structural loads. Always consult your local building department or a licensed engineer before construction.