Aquarium Volume & Stocking Calculator
Calculate fish tank volume in gallons. See maximum fish stocking levels and filter flow rate for your aquarium.
Calculating Aquarium Volume
For a rectangular tank: Length × Width × Height (all in inches) ÷ 231 = gallons. A standard 48×13×21" tank holds approximately 55 gallons. Account for substrate, rocks, and decorations — actual water volume is typically 10-15% less than the calculated total. Knowing your exact volume is crucial for medication dosing, water conditioner amounts, and equipment sizing.
Fish Stocking Guidelines
The classic "one inch of fish per gallon" rule is a rough starting point, not a precise rule. Better guidelines: small tetras and rasboras: 1" per gallon works. Cichlids and goldfish: need 2-3 gallons per inch due to higher bioload. Bettas: 5 gallon minimum despite their size. Filtration is the real limiter — a well-filtered, planted tank can support more fish than an unfiltered one. Use the 1" rule as a starting point and adjust based on species, filtration, and water test results.
Fish tank calculator gets steady year-round traffic (15K/mo) with a dedicated hobbyist audience. Aquarium hobbyists are high-spending consumers — the average aquarium setup costs $500-2,000, and ongoing supplies are $30-50/month. Pet supply advertisers (Petco, Chewy) pay $3-8 CPC.
