Cannabis Dryback Calculator

Measure container dryback by weight

Dryback describes how much water a root zone loses between irrigations. Weighing a representative container provides a practical way to track it. Enter the weight immediately after a complete irrigation and drainage period, the current weight, and a dry reference weight for the container, plant, and substrate.

The calculator treats the difference between fully watered and dry reference weights as available container water. It then reports how much of that range has been used. In the default example, the available range is 2.5 kilograms and 1.3 kilograms has been lost, producing 52% dryback.

Establish useful reference weights

Use the same scale, container, and support hardware every time. A fully watered reference should be taken after drainage has stabilized. The dry reference should represent the lowest acceptable root-zone water content, not a dangerously wilted plant. Plant growth adds weight over time, so references should be refreshed periodically.

Interpreting the result

A higher percentage means more of the measured water range has been used. It is not a universal irrigation target. Coco, rockwool, peat, and soil have different air-water relationships, and container size, root density, climate, and crop stage all matter.

Better dryback records

• Measure at consistent times relative to irrigation and lights.
• Track several representative plants, not only one.
• Note runoff, environmental changes, and plant response.
• Recheck references as biomass increases.

Use dryback alongside moisture sensors, runoff data, and visual plant health. This calculator is a monitoring aid, not a fixed watering prescription.