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Septic Tank Sizing Calculator

Minimum septic tank capacity by bedroom count.

Estimate the minimum septic tank capacity required by typical residential code, based on the number of bedrooms (each bedroom is assumed to add 250 gallons of capacity above a 750-gallon minimum).

Nadia Almasri By Nadia Almasri
Published Last reviewed 1 min read

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Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Recommended capacity = max(750, 750 + (bedrooms − 2) × 250) gallons.

In depth

Estimate the minimum septic tank capacity required by typical residential code, based on the number of bedrooms (each bedroom is assumed to add 250 gallons of capacity above a 750-gallon minimum).