Buy substrate by guesswork and you either come up short mid-scape or store leftover bags for years. This aquarium substrate calculator turns your tank footprint and the depth you want into the weight of gravel, sand or aqua soil to order.
Aquarium Substrate Calculator
Work out how much sand, gravel, or aqua soil you need for a given tank footprint and depth, in pounds and kilograms.
A common target is 1 to 2 inches of gravel for a fish-only tank and 2 to 3 inches for rooted plants. Weights are estimates; brands vary. Buy a little extra to slope the substrate higher at the back.
How deep should the substrate be?
For a plain gravel tank, one to two inches is plenty. Planted tanks want two to three inches so roots have something to hold, and aqua soil setups often slope from two inches at the front to three or four at the back for depth. Set your depth in the tool and it scales the amount to your exact footprint.
Gravel, sand and aqua soil weigh differently
The same volume of sand weighs more than gravel, and aqua soil weighs less than both because it is porous. That is why a weight estimate beats a generic “one pound per gallon” rule. Pick your material in the calculator and it uses the right density.
A note on sand depth
Keep sand beds under about two inches unless you are deliberately building a deep planted bed, and stir the top layer during cleaning. Deep, undisturbed sand can trap gas pockets. The tool warns you when your sand depth crosses into that territory.
Plan the whole scape
Substrate is the foundation for plants, so pair it with our picks for low-maintenance aquarium plants. Know your water volume before you order hardscape with the aquarium volume calculator, and when it is time to rinse and add it, the fish tank setup guide shows the order of operations. Keeping it clean later is covered in how to clean a fish tank. More tools live on the aquarium calculators hub.
Frequently asked questions
How much substrate do I need for my tank?
Roughly one pound of gravel per gallon gives about an inch, but weight varies by material and the depth you want. Enter your tank’s length, width and target depth above for an exact figure.
How many inches of substrate for a planted tank?
Two to three inches so roots can anchor. Slope it deeper at the back for a sense of depth.
Is gravel or sand better?
Gravel is more forgiving and lets water flow through; sand looks natural and suits bottom-dwellers but needs shallower beds and the occasional stir.