🪨 Aquarium Substrate Calculator
Enter your tank's length, width, and the depth you want, pick gravel or sand, and see how many pounds and kilograms of substrate to buy.
🧮 Calculate Your Substrate
What is a Substrate Calculator?
It tells you how much gravel or sand to buy to cover your tank's base to a chosen depth. Enter the length and width of the tank footprint and the depth you want, choose gravel or sand, and it works out the volume and converts it to a weight in both pounds and kilograms.
Sand is a touch denser than gravel, so it needs slightly more weight for the same depth. Because bagged substrate packs differently and you'll often slope it up at the back, round up and keep a spare bag so you don't run short partway through your aquascape.
❓ Frequently Asked Questions
How much gravel or sand do I need for my aquarium?
Multiply the tank's length × width × the substrate depth in inches to get the cubic inches of substrate, then convert to weight. Gravel weighs around 0.058 lb per cubic inch and sand around 0.062 lb per cubic inch. This calculator does the maths for both and gives the result in pounds and kilograms — just enter your tank footprint and desired depth.
How deep should the substrate be?
For most community tanks, 1–2 inches is plenty. Go toward the deeper end (2 inches or more) if you're growing rooted plants that need something to anchor in, and toward the shallow end for easier cleaning or a bare-look layout. Very deep substrate can trap waste and develop anaerobic pockets, so deeper isn't always better.
Is sand or gravel better for a freshwater tank?
Both work — it's mostly about your fish and plants. Sand suits bottom-dwellers like corydoras and loaches that sift it, and gives a natural look, but can compact. Gravel is easier to vacuum, lets water flow through, and anchors many plants well. Sand is slightly denser, so you'll need a little more weight for the same depth.
Why should I buy a little extra substrate?
Bagged substrate varies with grain size and how tightly it packs, and you'll often want to slope it up toward the back or build up planted areas, which uses more than a flat layer. Rounding up and keeping a spare bag means you won't come up short mid-aquascape or when topping up after cleaning.