Aquarium Volume Calculator: Find Tank Size in Gallons & Liters

Aquarium Volume Calculator

Enter your tank dimensions to find out its true water capacity.

Measure your tank's outside dimensions to find its standard gross capacity. Actual water volume will be slightly less due to glass thickness and decorations.

1. Choose Measurement Unit Centimeters (cm) Inches (in)

2. Enter Tank Dimensions

Length

Width

Height

Please enter valid positive numbers for all dimensions.

Calculate Volume

Estimated Capacity

0 Gallons

0 Liters

*Actual water volume will be slightly less due to substrate, decorations, and glass thickness.

MKO Aquatics Team

We are a team of passionate aquarists dedicated to modern, ethical fish keeping. With years of hands-on experience, our mission is to help beginners build thriving, balanced freshwater ecosystems without the guesswork.

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Why You Must Know Your Exact Aquarium Volume

Guessing your fish tank size is a dangerous game. Knowing your exact aquarium capacity in both gallons and liters is the most critical metric for any aquarist, directly impacting the health of your fish.

3 Reasons to Use a Tank Capacity Calculator:

• Safe Stocking Limits: The general “one inch of fish per gallon” rule only works if you actually know how many gallons you have. Overstocking causes fatal ammonia spikes.
• Accurate Medication Dosing: Fish medicines are heavily concentrated. Dosing a 20-gallon treatment into a tank that actually holds 15 gallons of water can be lethal.
• Weight Management: Water is heavy (about 8.3 lbs per gallon). A 50-gallon tank weighs over 400 lbs just in water weight, which requires a specialized stand, not a standard desk.

*Note: Our calculator determines the gross volume based on outside dimensions. Remember that thick glass, deep substrate layers, and large aquascape rocks will slightly reduce your actual net water volume.