Measuring VPD (Vapor Pressure Deficit) to Increase Your Cannabis Yield

VPD is a measurement technique describing the vapor pressure differential from inside the leaf, compared to the vapor pressure of the air in the room. Different crops need different levels of temperature, airflow, and humidity in their environment during different growth stages. Growers monitor and control their VPD to maintain the optimal temperature and relative humidity conditions in their grow rooms. With the right adjustments to temperatures and relative humidity, you can significantly increase your final yield!


Lowering the VPD generally means increasing the relative humidity, but high humidity in the grow room has its own risks. Ideally, cannabis crops should start with a lower VPD (.8-1.2 kPa) in the vegetative state. A dryer climate, or higher VPD, is essential during the later end of flowering to prevent molds and mildews.


Ready to get started?

  1. Using an Infrared temperature gun, take a reading from the leaf’s surface.
  2. Note the current reading of the room’s relative humidity.

Compare your measurements to our chart to see how close you are to optimal conditions!

pro gro vpd chart