Everyday tool
How many bags do you need for a sloped substrate bed? Estimate from average depth and a purchase allowance.
Bag counts use liters; weight is estimated from density
Average depth 2.3 in · difference 1.5 in
Substrate result
8 L × 2 = 16 L
Weight is estimated from average bulk density and can vary by grain size, moisture, and product. Bag counts use liters; if a product is sold only by weight, check the manufacturer's volume or density.
Substrate quantity
Add tank length/width and the front/rear substrate depths. The model uses their average, so complex terrain needs your own adjustment.
Use 100% for a full bed or enter the proportion you will cover. Extra allowance is added to the calculated volume.
Enter liters per bag to get a rounded-up count. For weight-only packaging, check product density before comparing estimated weight.
A worked example
The 6 cm average depth gives 11.88 L after allowance; dividing by 8 L rounds up to two bags.