How is substrate volume calculated?

Volume is simply length times width times depth — the footprint of the tank base multiplied by how deep you want the substrate. The tool converts your dimensions to a common unit, multiplies them, and reports the result in litres, the unit substrate bags are usually sold in.

How deep should aquarium substrate be?

For a fish-only tank 3 to 5 cm of gravel or sand is plenty. Planted tanks usually want 5 to 8 cm so root systems have room, often sloped deeper at the back. Going much beyond 8 cm risks anaerobic pockets unless you have burrowing livestock or a deep-sand-bed setup.

Why does the weight differ between sand, gravel, and aquasoil?

Each material has a different bulk density. Sand packs tightly at roughly 1.5 kg per litre, gravel sits around 1.6 kg per litre, and lightweight baked aquasoil is much lower at about 0.8 kg per litre. The same volume of each therefore weighs very differently, which matters for shipping and shelf load.

Should I buy extra substrate?

Yes, add about 10 percent. Bags settle and compact, you may want a deeper slope at the rear, and some material is lost rinsing out dust. Running short mid-setup means hunting for a matching bag later, so rounding up by a bag is cheap insurance.

Does tank shape change the calculation?

For standard rectangular tanks the length-by-width footprint is exact. Bow-front or hexagonal tanks have a slightly larger base area, so treat the result as a minimum and add a little extra. Always measure the inside dimensions, not the outside glass.

Aquarium Substrate Amount Calculator

Buy too little substrate and you are short mid-scape; buy too much and bags sit unused. This calculator turns your tank footprint and desired depth into a precise volume and weight for gravel, sand, or aquasoil, so you can order the right number of bags first time.

How it works

Substrate volume is the base footprint times the depth, then weight is volume times the material’s bulk density:

volume(L) = length(cm) × width(cm) × depth(cm) / 1000
weight(kg) = volume(L) × density(kg/L)

Typical bulk densities are about 1.6 kg/L for gravel, 1.5 kg/L for sand, and 0.8 kg/L for lightweight aquasoil. Dividing the litre figure by your bag size gives the number of bags, rounded up.

Example and tips

A 60 × 30 cm tank base with 5 cm of gravel is 60 × 30 × 5 / 1000 = 9 litres, about 14.4 kg of gravel. Add roughly 10 percent for settling, dust loss, and a deeper rear slope. Keep depth at 3 to 5 cm for fish-only tanks and 5 to 8 cm for planted tanks, and always measure the inside dimensions of the tank rather than the outer glass.