Aquarium Volume Calculator

What is the Aquarium Volume Calculator?

Calculate the water volume of a rectangular fish tank. Tank volume decides how many fish you can keep, how much water conditioner to add and which filter and heater to buy.

How to use the Aquarium Volume Calculator

1. Enter your length, your width, your height.
2. Results update automatically as you type; you can also press Calculate.
3. Read the output: us gallons, liters, water weight.
4. Use the 📊 chart to see the result visually, then copy or share it.

Formula and method

Worked example

With length = 36 in, width = 12 in, height = 16 in, the Aquarium Volume Calculator returns us gallons: 29.92; liters: 113.27; water weight: 250 lb.

Where the Aquarium Volume Calculator helps in real life

You bought a used 36 × 18 × 16-inch tank with no label. The calculator gives its volume in gallons so you can size the filter and dose treatments correctly.

Your water conditioner says one capful per 10 gallons. Knowing the real volume, not the rounded number on the box, avoids under- or over-dosing.

Common mistakes to avoid

• Measuring the outside glass instead of the inside.
• Using the full height when the water sits an inch or two lower.
• Forgetting that gravel and decorations displace water.
• Dosing medication by the tank’s nominal size.

💡 Practical tip: For medication doses, use the actual water volume after substrate and décor — it is often 10–20% less than the tank size.

Tips for better results

• Measure inside dimensions in inches.
• Subtract a little volume for substrate and rocks.
• Write the real volume on a label stuck to the stand.

⚠️ Material estimates are approximate. Follow local building codes and manufacturer instructions.

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