The word after the number matters
A bag labeled in liters can be compared directly with a liter result. A bag labeled in cubic feet needs a volume conversion. A quart label needs one more question: which quart? NIST’s tables distinguish the US dry quart from the US liquid quart. One dry quart is approximately 1.101221 liters; one liquid quart is approximately 0.946353 liters.
Our calculator includes both explicitly. Neither option is the British imperial quart. If the bag provides an equivalent liter amount, use that printed amount. If it only says quarts and the definition is unclear, check with the manufacturer instead of silently assuming a unit.
A shopping example
Suppose your measured containers need 70 liters of new mix. A 32 US dry-quart bag is approximately 35.24 liters, so the arithmetic calls for two bags. A 32 US liquid-quart volume is approximately 30.28 liters, so the same calculation calls for three. The different count comes from the unit, not a difference in the quality of the mix.
A cubic foot is approximately 28.31685 liters. A 2-cubic-foot bag therefore represents about 56.63 liters. Read the package’s net volume; shipping weight and the size of the parcel are not substitutes for that figure.
Separate quantity from suitability
The tool rounds the number of whole bags upward only after calculating the total for all identical pots. It does not round each individual pot to a separate bag. This avoids treating shared leftover mix as unusable.
Any optional extra percentage is your own planning choice, not a requirement. Recheck the bag label, the container measurements and the intended use before buying. A correct volume calculation cannot tell you whether the contents suit your plant or planter. Keep a photo or written note of the label for your own records so that next season’s estimate uses the same units.
Sources for factual statements
Planning methods and fictional worked examples are our own analysis. No physical product testing or harvest results are claimed. Use guidance for your actual plant, location and equipment. Read our research method.