FishMaths

Substrate calculator

Enter the tank footprint and the depth you want. You'll get how much gravel, sand or soil to buy.

For a flat bed, use the same number for both.

Result
0
Enter your numbers

How the math works

The calculator multiplies length by width by the average depth to get the volume of substrate. It then uses a typical weight per liter for each type. Gravel and sand run heavy. Aquasoil is much lighter, which is why soil bags are sold by the liter.

How deep should substrate be?
About 1 to 2 inches (2.5 to 5 cm) for most fish-only tanks. Planted tanks often use 2 to 3 inches, deeper at the back.
Is there a quick rule of thumb?
Roughly 1 pound of gravel per gallon gives about 1 inch of depth in a standard tank. Tall tanks need less, long shallow tanks need more.
Why buy a little extra?
Substrate settles, and weights vary between brands. An extra bag saves a second trip to the store.