Aquarium substrate calculator
A gravel calculator for any fish tank: find out how much gravel, sand or aquasoil to buy, in pounds, kilograms and bags.
How to calculate substrate for an aquarium
The calculator multiplies your tank's floor area by the depth you want, then converts that volume to weight using a typical bulk density: about 100 lb per cubic foot for gravel and 95 lb for sand. Plant substrates are light and sold by volume, so they are shown in litres.
Aquarium gravel calculator
Choose Gravel to use the aquarium gravel calculator. A handy check: a 1 inch layer of gravel over 1 square foot of floor weighs about 8 lb. A standard 29 gallon has 2.5 square feet of floor, so a 2 inch bed needs about 42 lb.
Aquarium sand calculator and sand bed depth
Choose Sand for the aquarium sand calculator. Sand packs slightly lighter than gravel by volume. Freshwater sand beds are usually 1–2 inches; reef keepers use a shallow bed under an inch or a deep sand bed of 4 inches or more.
Recommended substrate depth
| Tank type | Typical depth |
|---|---|
| Community tank with gravel | 1–2 in (2.5–5 cm) |
| Planted tank | 2–3 in (5–7.5 cm), deeper at the back |
| Sand for corydoras and loaches | 1–2 in (2.5–5 cm) |
| Reef sand bed | 1–2 in shallow, or 4 in+ for a deep sand bed |
Popular tank sizes
- How much gravel for a 29 gallon tank
- How much gravel for a 40 gallon breeder
- How much gravel for a 55 gallon tank
- How much gravel for a 75 gallon tank
Need the tank's volume first? Use the aquarium volume calculator. Not sure of your tank's floor size? Learn how to measure a fish tank or look it up in the tank size chart.
Frequently asked questions
How much gravel do I need per gallon?
A common shortcut is about 1 lb of gravel per gallon for a 1 inch bed, but it depends on the tank's footprint, not its volume. Tall tanks need less, wide tanks need more. Use the calculator for an exact figure.
How deep should aquarium gravel be?
1 to 2 inches suits most community tanks. Planted tanks usually need 2 to 3 inches so roots have room. Sand beds are commonly 1 to 2 inches.
How many bags of gravel for a 55 gallon tank?
A standard 55 gallon has a 48 x 13 inch floor. A 2 inch gravel bed needs about 72 lb, which is four 20 lb bags.
Is sand heavier than gravel?
By volume they are similar: aquarium sand and gravel both weigh roughly 90 to 100 lb per cubic foot. Specialist plant substrates are much lighter and are sold by litres.