Flat and sloped bed formulas
For a flat bed, multiply internal length, width, and depth in centimeters, then divide by 1,000 for liters. For a slope, use the average of front and back depth.
Use internal dimensions rather than the outside glass size.
- Flat liters = length × width × depth ÷ 1,000
- Sloped liters = length × width × average depth ÷ 1,000
Example for a 60 cm aquarium
A 60 × 30 cm floor sloping from 3 cm to 8 cm has an average depth of 5.5 cm and a base volume of 9.9 L.
Adding a 10% margin gives about 10.9 L, and bag count rounds up to the product's package size.
Why liters and kilograms differ
Soil, sand, and gravel have different bulk densities. Use the package's volume, weight, or density instead of assuming one liter equals one kilogram.
Wet and dry material also differ, and stand loading should include glass, water, rocks, and equipment separately.
Layouts with rocks and structures
Large rocks, wood, and undergravel structures are not automatically subtracted. Reduce the estimate when they occupy a meaningful part of the base.
Rounding up prevents shortages, so some unused material is normal.