Substrate Volume & Weight Calculator
Calculate how much substrate (sand, gravel, soil) you need from your tank's footprint and desired depth, using your substrate's density to estimate total weight. Works for both aquariums and terrariums.
A box of substrate, weighed
volume (cu ft) = length × width × depth / 1728
weight (lb) = volume × density (lb/cu ft)1,728 is the number of cubic inches in a cubic foot. A 24 × 12 in tank with 2 in of substrate is 576 cubic inches, or 0.333 cu ft; at 100 lb/cu ft that is 33.3 lb - two 20 lb bags with a little spare. Depth is the input people get wrong: going from 2 in to 3 in is another 17 lb, because weight scales straight with depth.
Density and depth
| Substrate | Density |
|---|---|
| Aquarium sand | 90-110 lb/cu ft |
| Gravel, 2-5 mm | 85-100 lb/cu ft |
| Baked aquasoil | 50-60 lb/cu ft |
| Coco coir / terrarium mix | 20-40 lb/cu ft |
- 1-2 in is plenty for a bare or lightly planted tank, and it stays easy to vacuum clean.
- 2-3 in suits rooted plants such as swords and crypts; deep beds of fine sand can go anaerobic if never disturbed.
- Terrariums want this depth plus a separate drainage layer below it, so calculate the two layers separately.
Frequently asked questions
How much sand do I need for a 24 × 12 inch tank?
About 33 lb for a 2 in bed, at sand's typical 100 lb per cubic foot. That footprint is a standard 15 gallon, so 30-35 lb covers it.
How deep should aquarium substrate be?
An inch or two for most tanks, two to three where plants root. Deeper looks good but buries waste out of reach of a gravel vacuum.
What density should I enter for my substrate?
If the bag gives weight and volume, divide one by the other. Otherwise start at 100 lb/cu ft for sand or gravel and around 55 for a bagged aquasoil, which is far lighter than it looks.