Aquarium Gravel Calculator
Estimate how much gravel or substrate your fish tank needs. Enter the tank length, width and substrate depth to get the weight in pounds and kilograms and the volume in litres.
Aquarium Gravel Calculator Tool
How much gravel for an aquarium?
Aquarium gravel is estimated from the footprint of the tank (length × width) and the substrate depth, not the water volume. Common depths:
- 1–2 inches for a basic gravel bed or non-planted tank.
- 2–3 inches for rooted live plants so roots can anchor.
Volume = Length × Width × Substrate depth
Weight = Volume × substrate density
Quick rule of thumb
A widely used estimate is about 1 to 1.5 lb of gravel per US gallon for a roughly 2 inch bed. For a deeper planted substrate, use closer to 2 lb per gallon. The calculator above uses your actual tank dimensions for a more accurate figure.
Common tank sizes
| Tank | Footprint | Gravel for 2" bed |
|---|---|---|
| 10 gal | 20 × 10 in | ≈ 10–12 lb |
| 20 gal | 24 × 12 in | ≈ 15–20 lb |
| 40 gal | 36 × 18 in | ≈ 35–45 lb |
| 55 gal | 48 × 13 in | ≈ 35–50 lb |
Frequently asked questions
How much gravel do I need for a fish tank?
Estimate from the tank's length × width × substrate depth. A common rule is about 1–1.5 lb of gravel per US gallon for a 2 inch bed. Enter your tank size above for an exact figure.
How deep should aquarium gravel be?
1–2 inches for a basic substrate, or 2–3 inches for live rooted plants so the roots can anchor and access nutrients.
How much gravel for a 20 gallon tank?
Roughly 15–20 lb for a standard 20 gallon (24 × 12 in) tank at a 2 inch depth. Use more for a planted tank.
Is aquarium gravel measured by water volume?
No — it is based on the tank's footprint (length × width) and the substrate depth, not the gallons of water. The per-gallon rule is just a quick approximation.
More gravel calculators
Disclaimer: Aquarium substrate estimates are approximate and depend on grain size and how level the bed is. Round up so you can shape the substrate and slope it toward the back.