Guides
How Much Aquarium Substrate Do I Need?
Work out exactly how much gravel, sand or aqua soil your tank needs, the right depth, and how many bags to buy.
Read more →Fish Tank Surface Area Calculator
Surface area
—
Enter your tank dimensions to see the volume.
Did we solve your problem?
Work out the water surface area of your aquarium, which affects oxygen exchange. Enter the dimensions to see the surface area and the full volume.
Why surface area matters
The water surface is where oxygen enters and carbon dioxide leaves, so it is length times width for a rectangular tank. A wide, shallow tank holds more oxygen than a tall, narrow one of the same volume.
Water surface area
The water surface is length times width. Adjust the sides to see the area.
Surface area = 1,800 cm²
Formula
V = length × width × height Related calculators
Frequently asked questions
How do I calculate fish tank surface area?
For a rectangular tank, multiply length by width. That is the top opening where gas exchange happens.
Why is surface area important for fish?
A larger surface lets more oxygen dissolve, which supports more fish and healthier water.
Is a tall tank worse for oxygen?
A tall, narrow tank has less surface for its volume, so it holds less oxygen than a wide tank of the same size.
How does surface area relate to stocking?
Some aquarists stock by surface area rather than volume, allowing roughly a set length of fish per area of surface.
What units can I use in this calculator?
You can switch between centimetres, millimetres, inches, feet and metres at any time. Enter all dimensions in the same unit and the result updates instantly.
Does the result include substrate and decoration?
The figure is the full internal capacity. Subtract roughly 10 to 15 percent for substrate, rocks and the gap you leave at the top to estimate the real water volume.
How accurate is this fish tank calculator?
It uses the exact geometric formula for each shape, so the result is accurate for the dimensions you enter. Measure the inside of the tank for the best accuracy.
Is this calculator free to use?
Yes. It is completely free, needs no sign-up, and works on phones, tablets and desktops.
Related guides
Learn the core ideas behind fish tank volume before or after using the calculator.
Care Guides
What Size Tank Does a Betta Fish Need?
Bettas do not belong in bowls. The real minimum tank size for a betta in litres and gallons, plus heater, filter and tank mate advice.
Read more →Equipment Guides
What Size Heater Does My Aquarium Need?
Pick the right aquarium heater wattage for your tank size and room temperature, with a simple watts-per-litre rule and a free heater calculator.
Read more →