Aquarium Substrate Calculator

How this calculator works

The math is a simple volume calculation: footprint (length × width) times your target depth gives a volume in cubic inches, which converts to gallons of loose material. Multiplying by a bulk density figure (pounds per gallon, which varies by material because grain size changes how tightly it packs) gives an estimated weight.

Why sand needs more weight than gravel for the same depth

Sand grains are smaller and pack more tightly than gravel, leaving less air space between particles, so a given volume of sand weighs noticeably more than the same volume of gravel. Aquasoil is the opposite: it's a porous, lightweight fired material, so the same depth takes less weight than either sand or gravel.

Choosing a target depth

A thin 1–2 in layer is common for a simple gravel-bottomed community tank. Planted tanks generally want 2–3 in at the front sloping to 3–4 in at the back to give root systems room and to build in a slope for depth perception. Bare-bottom or minimal-substrate setups (some cichlid and shrimp tanks) may use less than an inch, mainly for beneficial bacteria surface area rather than plant support.

Source: Bulk density figures are typical values published across aquarium substrate manufacturer product specs for gravel, sand and aquasoil.