Septic Tank Capacity & Sizing Calculator
Enter your home's bedrooms, occupants, and appliance usage to get the minimum recommended tank size in gallons and your ideal pump-out interval — updated in real time.
1. Household Profile
Adjust each factor to match your home. Results update in real time.
2. Your Tank Sizing Results
- • Your system is well-matched to your household. Maintain monthly biological treatments to keep sludge accumulation minimal.
Standard Tank Size Guide
| Bedrooms | Min. Tank | Pump Interval* |
|---|---|---|
| 1–2 | 750 gal | 5–7 yrs |
| 3 | 1,000 gal | 3–5 yrs |
| 4 | 1,200 gal | 3–4 yrs |
| 5+ | 1,500+ gal | 2–4 yrs |
*For a household of 4 without garbage disposal. Intervals vary by occupancy.
Extend Your Pump-Out Interval With Biological Treatment
Consistent biological treatment reduces sludge accumulation by 40–55%, directly extending the years between expensive pump-outs. See our ranked comparison of the best biological sludge dissolvers for your tank size.
View Best Sludge Dissolvers for 2026 →Disclaimer: Recommendations are based on EPA standard design tables and widely adopted building codes. Local requirements vary by state and county. Consult a licensed septic engineer or your local health department before purchasing or installing a septic system.