Septic Calculators
Reviewed
Each calculator uses published rules: state septic codes, the extension pumping table and EPA cost figures. A "How we calculated this" panel lists every source behind your result. Use them to check a quote, a permit design or a pumping schedule.
Planning a new or replacement system
- Septic Tank Size CalculatorTank size from bedrooms, people, disposal and your state's code minimum — with the math shown.Typical: 1,000–1,500 gal
- Septic System Cost CalculatorInstalled cost by system type from EPA figures in today's dollars, with permit fees and a market cross-check.Conventional: ~$7,000–$14,000
Maintaining the system you have
Frequently asked questions
Are these calculators accurate enough to order a tank?
No. Your permit sets the legal tank size and system design after a soil evaluation. The calculators show what the rules and published data suggest, so you can check a design or a quote.
Where do the numbers come from?
From state septic codes, university extension publications and EPA documents. Each result lists its sources, and our sources page lists every source the site uses.
Do the calculators store what I enter?
No. They run entirely in your browser and nothing you type is sent anywhere.