Septic Drain Field Calculator
Estimate preliminary septic absorption area, total trench length, trench count, reserve field and installation cost from user-entered design flow and soil loading rate.
Default project preview
500 ft²
Total trench length
166.7 ft
Trench count
3
Average trench length
55.6 ft
Reserve field
500 ft²
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Design flow = occupants × flow per person. Absorption area = design flow ÷ approved soil loading rate. Trench length = absorption area ÷ effective trench width.
FAQ
Septic Drain Field Calculator questions
Where does the soil loading rate come from?+
It must come from an approved site and soil evaluation under the applicable local process.
Is the reserve field installed immediately?+
Requirements vary. The calculator reports the entered reserve percentage as protected site area.
Does trench length include spacing between trenches?+
No. It is absorption trench length only; separation and setbacks affect the overall site footprint.