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Aquarium Volume and Stocking Calculator

Calculate your aquarium's water volume in gallons and a simplified fish stocking estimate using the classic inch-per-gallon guideline.

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in
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The classic "1 inch of fish per gallon" guideline — a rough starting point for small freshwater community fish only.
Tank volume —
Rough max adult fish length —
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About the Aquarium Volume and Stocking Calculator

Tank volume is found the same way as any rectangular container's volume, then converted from cubic inches to US gallons. The stocking estimate applies the well-known (and simplified) "inch per gallon" hobbyist guideline.

Formula: Volume (gallons) = (Length × Width × Water Height in inches) ÷ 231. Max Fish Inches = Volume ÷ Stocking Ratio

The inch-per-gallon rule is only a rough starting point for small, slim-bodied freshwater community fish — it ignores bioload, adult body shape, swimming space and filtration, so always research a species' actual care requirements before stocking.

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