Inputs used
- Tank length (cm)
- Tank width (cm)
- Desired substrate depth (cm)
- Substrate density (kg/L)
- Bag size (kg)
aquarium substrate calculator
How the Aquarium Substrate Calculator works
Assumptions, formula, inputs, and practical limits for the Aquarium Substrate Calculator.
How this estimate works
The calculator turns tank footprint and desired depth into volume, converts that volume to weight using substrate density, then rounds bag count up.
- Volume in litres = length x width x depth in cm divided by 1000.
- Weight = volume x substrate density x a 10% setup allowance.
- Bag count is always rounded up to avoid running short during layout.
Outputs generated
- litres of substrate
- kg/lb required
- bag count
- depth guidance
Worked example
A 90 x 45 cm tank with 5 cm of substrate needs about 20.3 litres. At 1.4 kg/L with a small allowance, that is about 31.2 kg, so four 9 kg bags.
Substrate depth examples
Depth depends on layout, livestock, plants, and the substrate type. These examples are planning ranges, not species guidance.
| Tank footprint | Depth | Approximate volume |
|---|---|---|
| 60 x 30 cm | 3 cm | 5.4 litres |
| 60 x 30 cm | 5 cm | 9 litres |
| 90 x 45 cm | 5 cm | 20.3 litres |
| 120 x 45 cm | 6 cm | 32.4 litres |
Before you add substrate
- Decide whether the layout is flat, sloped, or planted before estimating depth.
- Check whether the substrate should be rinsed before use.
- Confirm the bag weight and density for the exact brand.
- Leave enough free space for hardscape, filters, and livestock needs.
When this estimate may be wrong
- Sloped aquascapes and deep planted areas can use more substrate than a flat average depth.
- Rocks, wood, and decor displace substrate and water volume.
- Some livestock need specific substrate types or depths that a volume calculator cannot decide.
Limits of the estimate
Substrate depth depends on livestock, plants, and tank design. Check species-specific requirements.
Check the needs of your livestock and plants, then confirm bag weights and substrate density from the brand you plan to use.