Septic Tank & Drainfield Sizing Calculator
Estimate residential septic tank minimum capacity (gallons) and absorption drainfield trench square footage based on bedrooms and soil perc rate.
- 100% free
- Private in browser
- No signup
- No watermarks
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About Septic Tank & Drainfield Sizing Calculator
Estimate residential septic tank minimum capacity (gallons) and absorption drainfield trench square footage based on bedrooms and soil perc rate. Enter Number of Bedrooms in Home, Design Flow per Bedroom and Soil Perc Rate and the tool works out Recommended Septic Tank Size, Daily Wastewater Flow and Required Drainfield Trench Area straight away. Everything runs in your browser, so your data never leaves your device.
How to use Septic Tank & Drainfield Sizing Calculator
- Enter Number of Bedrooms in Home, Design Flow per Bedroom and Soil Perc Rate.
- Adjust the remaining options (Drainfield Trench Width) to match your case.
- Read Recommended Septic Tank Size, Daily Wastewater Flow and Required Drainfield Trench Area in the results panel — copy or download what you need.
Key features
- Shows Recommended Septic Tank Size (Gallons)
- Shows Daily Wastewater Flow (Gallons/Day GPD)
- Shows Required Drainfield Trench Area (Sq Ft)
- 4 adjustable inputs, results update as you type
- No signup, no limits
Frequently asked questions
- Is this calculation free and private?
- Yes, 100% of calculations execute locally in your web browser. No inputs or personal data are stored or transmitted.
- What does the Septic Tank & Drainfield Sizing Calculator give me?
- It works out Recommended Septic Tank Size, Daily Wastewater Flow, Required Drainfield Trench Area and Total Trench Pipe Length, updating live as you change the inputs.
- What do I need to enter?
- Just Number of Bedrooms in Home, Design Flow per Bedroom, Soil Perc Rate and Drainfield Trench Width. Every field has a sensible default you can start from.
- Is my data uploaded anywhere?
- No. The calculation runs in your browser with JavaScript — nothing you type is sent to a server or stored.
- Does it work on a phone?
- Yes. The layout adapts to small screens and needs no app or signup.
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