The calculator automatically factors in these ramps and provides your Daily Light Integral (DLI), or the total light delivered to your crop, in µmol·m⁻²·s⁻¹, enabling you to fine-tune light intensity and duration for optimal plant growth and productivity.

The calculator outputs the VPD in kilopascals (kPa). A higher VPD means drier air and stronger transpiration pull, while a lower VPD means more humid air and weaker transpiration. Maintaining an appropriate VPD helps plants transpire efficiently, absorb nutrients effectively, and maintain healthy water balance for strong growth. For optimal cannabis growth, maintain VPD in the range of 0.8–1.2 kPa during vegetative growth to encourage strong transpiration and nutrient uptake. In early flowering, increase slightly to 1.2–1.4 kPa to reduce humidity and mold risk, then target 1.4–1.6 kPa in late flower to maximize resin production and prevent bud rot. Lower VPDs (<0.8) may be useful for newly rooted clones to reduce stress.