Gravel calculator
Aquarium gravel calculator
Gravel is the most common freshwater substrate, and it is also the heaviest per bag. Enter the inside dimensions of your tank and the depth you want to get an exact weight in pounds and kilograms.
Substrate calculator
How much gravel do I need?
Gravel is calculated at 100 lb per cubic foot — the standard density for open-grain aquarium gravel.
Result
of aquarium gravel needed
- Metric weight
- 0 kg
- Volume
- 0 in³
- Water volume
- 0 L
- Bags to buy
- 0
Guide
Working out gravel by hand
The maths behind every aquarium substrate calculator is the same three-step chain. Multiply the inside length of the tank by its width to get the footprint in square inches, multiply that by the depth of the bed to get cubic inches, then divide by 1,728 to convert to cubic feet. Gravel settles at roughly 100 pounds per cubic foot, so one more multiplication gives you the weight to buy.
A standard 10 gallon has a 20 × 10 inch floor. Two inches of gravel is 400 cubic inches, which is 0.23 cubic feet — about 23 pounds. The same depth in a 55 gallon with its 48 × 13 inch floor needs 1,248 cubic inches, or roughly 72 pounds. That is the answer to how many pounds of gravel for a 10 gallon tank, and it scales straight up with the footprint.
How deep should gravel be?
One to two inches is plenty for a community or fish-only tank, because nothing is rooting into it. Planted setups want two to three inches so stems can anchor, and aquascapers commonly slope the bed from about one inch at the front glass up to three inches at the back. Deeper than four inches in an unplanned tank invites compacted, anaerobic layers that hold fish waste and smell of rotten eggs when disturbed.
Buying gravel by the bag
Gravel is sold in 5, 10, 20 and 25 pound bags, and the weight on the label is dry weight — it will settle a little once water and bacteria work into the gaps. Round the calculator result up to whole bags and add one spare, then rinse the lot in a bucket of cool water until it runs clear. The dust that comes off new gravel is what clouds a freshly filled tank.
If you are weighing up materials, compare against theaquarium sand calculator and theaquarium soil substrate calculator — the same two-inch bed can be 40 % lighter depending on what you pour in. For depth problems in reverse, try theaquarium substrate depth calculator.