Count sump and canister water too
Use the water you measured going in, or a volume worked out from inside measurements, with gravel, decor and any sump or canister water counted once. The gallon number on the label isn’t that.
How many buckets
Full containers plus the final partial amount add up to the selected water change. The trip count rounds up only when there is water left for a partial container. Zero percent returns zero water and zero trips; it does not recommend skipping needed care.
Prepare the route and replacement water
Choose the amount using your care plan. Follow the cleaning and water-change sequence, including unplugging equipment, and use the exact conditioner instructions when applicable. This calculator gives no dose, frequency or water-quality verdict.
Compare siphons, containers and hose routes before deciding what is practical to carry.