Aquarium Substrate Calculator
Calculate exactly how much gravel, sand, or planted tank substrate you need in pounds and bags. Compare all substrate types side by side.
Standard Gravel Needed
Total Weight
33.4 lbs
Using 5 lb bag
7 bags
(35.0 lbs total)
Using 25 lb bag
2 bags
(50.0 lbs total)
Using 50 lb bag
1 bag
(50.0 lbs total)
Based on a 24" x 12" tank at 2" substrate depth.
Substrate Comparison
| Substrate | Type | Lbs Needed | Smallest Bag | Largest Bag |
|---|---|---|---|---|
| Standard Gravel | gravel | 33.4 | 7 x 5 lb bag | 1 x 50 lb bag |
| Pea Gravel | gravel | 31.7 | 7 x 5 lb bag | 2 x 25 lb bag |
| Play Sand | sand | 30.0 | 1 x 50 lb bag | 1 x 50 lb bag |
| Pool Filter Sand | sand | 31.1 | 1 x 50 lb bag | 1 x 50 lb bag |
| Aragonite Sand | sand | 32.3 | 4 x 10 lb bag | 1 x 40 lb bag |
| Fluval Stratum | planted | 18.4 | 5 x 4.4 lb bag | 2 x 17.6 lb bag |
| Eco-Complete | planted | 23.0 | 2 x 20 lb bag | 2 x 20 lb bag |
| Crushed Coral | coral | 28.8 | 3 x 10 lb bag | 1 x 40 lb bag |
Recommended Substrates
How It Works
The calculator multiplies your tank's length x width x desired substrate depth (all in inches) to get the cubic volume, then multiplies by the substrate's density (pounds per cubic inch) to determine the total weight needed.
- Different substrates have different densities, so 2 inches of sand weighs differently than 2 inches of Fluval Stratum
- The comparison table lets you see exactly how much of each substrate type you would need for the same tank
- Bag counts are rounded up so you always have enough
Frequently Asked Questions
How deep should aquarium substrate be?
For most tanks, 1.5 to 2 inches of substrate is ideal. Planted tanks benefit from 2 to 3 inches to give roots room to anchor. Deeper substrate (3+ inches) can develop anaerobic pockets that produce toxic hydrogen sulfide gas, so avoid going too deep unless you are using an under-gravel filter or have Malaysian trumpet snails to aerate it.
How many pounds of gravel per gallon do I need?
A common rule of thumb is 1 to 1.5 pounds of gravel per gallon for a 2-inch bed. However, this varies by tank shape since a tall, narrow tank needs less substrate than a wide, shallow tank with the same volume. Our calculator uses your exact tank dimensions for a precise answer.
What substrate is best for planted aquariums?
Active substrates like Fluval Stratum, ADA Amazonia, or Eco-Complete are best because they provide nutrients and often buffer pH downward, which most tropical plants prefer. Inert substrates like gravel or sand can work with root tabs and liquid fertilizers but require more maintenance.
Can I mix different substrate types?
Yes, but with caveats. A popular approach is to put a nutrient-rich substrate on the bottom and cap it with sand or fine gravel. Over time, the layers may mix when you plant or vacuum. Avoid mixing sand and large gravel, as sand will sift to the bottom and create dead zones.