Calculate Septic Tank Size
Results
Suggested Tank Dimensions
Soakaway Area Needed
How this septic tank size calculator works
We estimate daily wastewater flow, multiply by retention time, and apply a safety factor. Minimum capacity is enforced for typical bedroom counts. Soakaway area is sized using soil absorption rates. Switch units to get septic tank size in feet or meters instantly.
Sizing basics
Use this quick guide to understand what each input means and why it affects septic tank size.
- Region preset: sets typical daily water use for that country/region.
- Bedrooms vs occupants: bedrooms set minimum capacity; occupants set daily flow.
- Daily flow per person: higher usage increases tank volume.
- Retention days: longer retention increases required volume.
- Safety factor: adds a buffer for peak usage and future changes.
- Soil absorption: controls soakaway size based on soil drainage.
- Units: switch between meters/liters and feet/gallons instantly.
FAQ
What size septic tank do I need?
Most homes need 1,000–1,500 gallons (3,800–5,700 L), depending on occupants and local requirements. Use the calculator for a tailored estimate.
Is this septic tank size calculator accurate for my country?
It uses common design practices and region presets. Always verify with local codes (e.g., USA, UK, Australia, NZ, Philippines, India, Ontario).
Do I need a soakaway size calculator?
If your system includes a leach field or soakaway, yes. Soil type and percolation rate are critical for sizing.