Aquarium Stocking Calculator

Calculate water volume and find the ideal number of fish for your tank. Supports multiple shapes and units.


Dimensions

Volume

Species

Stocking
Gravel, rocks, and decorations reduce actual water volume.

Actual Water Volume

45.0 Gallons

170.3 Liters

Add Fish to Your Stocking Plan

Stocking Summary: No fish added

Recommended Maximum: 0 inches of fish

How This Aquarium Calculator Works

This tool calculates actual water volume after accounting for substrate and decor displacement. It uses the standard "1 inch of fish per gallon" rule as a baseline, adjusted for species-specific needs. For example, goldfish produce more waste and require 2-3x more space.

  • Rectangular: L × W × H / 231 (gallons)
  • Cylindrical: π × (D/2)² × H / 231
  • Half Cylinder: (π × (D/2)² × L) / 2 / 231
  • Bow Front: Rectangular volume + 15%

Aquarium Stocking FAQ

Is the "1 inch per gallon" rule accurate?

It's a good starting point for small, slender fish. Larger fish, messy eaters (like goldfish), and territorial species require more space. Always research individual species.

Why subtract for substrate and decor?

Gravel, rocks, driftwood, and plants displace water. A 10-15% reduction is typical for moderately decorated tanks.

Do I measure the fish with or without the tail?

Standard practice is to measure the fish's standard length (excluding the tail fin) or total length. This calculator uses total length for simplicity.

Why are there both gallons and liters?

US gallons are standard in the aquarium hobby, but liters are used internationally. The calculator displays both for convenience.

Can I exceed the recommended stocking level?

Experienced aquarists with over-filtration and frequent water changes can sometimes exceed the guideline. For beginners, staying under the limit is safest.

Is my tank data saved?

All calculations happen in your browser. No data is stored or transmitted.