Aquarium Gravel Calculator
Work out how much substrate your fish tank needs. Enter your tank's dimensions (or its size in gallons) and how deep you want the bed to get the weight in pounds, kilograms, and bags.
For a 24" × 12" tank with a 2" bed of aquarium gravel, you need about 33.3 lb.
Estimate for planning. Rinse new substrate before adding it, and buy a little extra so you can slope it higher at the back.
How much gravel do I need for my aquarium?
Substrate is based on the tank's footprint — its length times its width (front to back) — multiplied by how deep you want the bed. Multiply length × width × depth in inches, divide by 1,728 to get cubic feet, then multiply by about 100 lb per cubic foot for gravel. A quick rule of thumb is roughly 1 to 2 pounds of gravel per gallon for a 1–2 inch bed, but tank shape varies, so the dimensions give the most exact figure. Enter yours above.
How deep should aquarium gravel be?
For most community tanks, 1 to 2 inches of gravel is plenty — enough to cover the bottom and anchor decorations. Planted tanks want 2 to 3 inches so roots have something to grab. Avoid going much deeper than 3 inches in a non-planted tank: gas can build up in the lower layers and turn anaerobic.
Gravel or sand for a fish tank?
Gravel is easy to vacuum and works for most community setups. Sand looks natural and suits bottom-dwellers like corydoras and loaches, but it compacts and needs gentler cleaning. Planted tanks often use a nutrient substrate capped with gravel or sand. Sand is a little heavier than gravel by volume, which the calculator accounts for when you pick it.
Rinse before you add it
New gravel and sand are dusty and will cloud your water. Rinse the substrate in batches under running water until it runs clear before adding it to the tank. Buy a little extra so you can slope the bed higher toward the back for depth and easier planting.
Gravel needed by tank size (2-inch bed)
| Tank | Footprint | Gravel (~2 in) |
|---|---|---|
| 10 gallon | 20 × 10 in | ~23 lb |
| 20 gallon (high) | 24 × 12 in | ~33 lb |
| 29 gallon | 30 × 12 in | ~42 lb |
| 40 gallon breeder | 36 × 18 in | ~75 lb |
| 55 gallon | 48 × 13 in | ~72 lb |
| 75 gallon | 48 × 18 in | ~100 lb |
For a 2-inch bed of gravel (~100 lb/ft³). Deeper beds and sand need a bit more.
Worked examples
- 30 in × 12 in = 360 sq in
- 360 × 2 in = 720 cu in
- 720 ÷ 1,728 = 0.42 cu ft
- × 100 lb/ft³ ≈ 42 lb
- 48 in × 13 in = 624 sq in
- 624 × 2 in = 1,248 cu in
- 1,248 ÷ 1,728 = 0.72 cu ft
- × 100 lb/ft³ ≈ 72 lb
Common mistakes to avoid
- Making the bed too deep. More than 2–3 inches in a non-planted tank traps waste and gas in the lower layers, which can go anaerobic. Keep it 1–2 inches unless you're planting.
- Not rinsing the substrate. New gravel and sand are coated in dust that clouds the water for days. Rinse until the water runs clear before adding it.
- Wrong substrate for the setup. Rooted plants want finer sand or a planted substrate; coarse gravel lets waste sink and rot. Match the substrate to your fish and plants.
- Buying by gallons alone. Two tanks with the same gallon rating can have different footprints. The tank's length, width and bed depth are what actually set the amount.
Frequently asked questions
How many pounds of gravel per gallon?+
Roughly 1 to 2 pounds per gallon for a 1–2 inch bed; deeper beds need more. For an exact figure, enter your tank's length, width and substrate depth above.
How much gravel for a 10, 20 or 55 gallon tank?+
At a 2-inch bed, about 23 lb for a 10-gallon, ~33 lb for a 20-gallon, and ~72 lb for a 55-gallon. See the tank-size table above, or enter your own dimensions.
How deep should the gravel be?+
1 to 2 inches for most tanks, 2 to 3 inches for planted tanks. Deeper than 3 inches risks anaerobic pockets in a non-planted tank.
Should I use gravel or sand?+
Gravel is easiest to clean and fine for community tanks; sand suits bottom-dwellers and looks natural but compacts. Planted tanks often use a nutrient substrate capped with gravel or sand.