Septic Tank Size Calculator
Tank capacity for your household.
Enter your values
ⓘ Live results
Results
- Recommended tank size
- 1,000 gallons
- Daily wastewater flow
- 280 gallons
- Minimum by bedroom count
- 1,000 gallons
- Retention time target
- 48 hours minimum
- Pump-out interval estimate
- 0.5 years
Quick answer
Most codes require at least 1000 gallons for a three bedroom home, rising with bedroom count and daily flow.
How to use the Septic Tank Size Calculator
- 1Enter the number of bedrooms — most codes size on this.
- 2Enter actual occupants and water use.
- 3Use the larger of the two figures.
Worked example
Using the values the calculator loads with:
Inputs
- Bedrooms3
- Occupants4
- Water use per person70 gal/day
Results
- Recommended tank size1,000 gallons
- Daily wastewater flow280 gallons
- Minimum by bedroom count1,000 gallons
- Retention time target48 hours minimum
- Pump-out interval estimate0.5 years
Frequently asked questions
How often should I pump?
Every 3–5 years for a typical family of four.
Does a garbage disposal matter?
Yes — it adds solids, so consider a larger tank.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.