Short answer
A cannabis yield calculator estimates dry flower weight from a few inputs: plant count, grow area, light wattage, and an assumed grams-per-watt or grams-per-plant value. The output is a planning figure. Actual harvest depends on genetics, light, temperature, humidity, nutrition, training, and harvest timing.
Best Cannabis Yield Per Plant: 5 High-Yield Strains Compared
Common formulas
- By light: dry grams = light watts x grams per watt x (1 - loss rate).
- By plant count: dry grams = plants x grams per plant x (1 - loss rate).
- By area: dry grams = square feet x grams per square foot x (1 - loss rate).
The loss rate accounts for trim, stems, mold, and test samples. A common planning range is 10% to 20%.
how much cannabis does one plant yield
Inputs that move the number
Light intensity and daily light integral set the ceiling for yield. Plant density changes competition for light. Vegetative time changes plant size at flip. Container size limits root volume. Temperature and vapor pressure deficit affect transpiration and flower development. Genetics set flower structure and finish time.
cannabis yield per plant guide
Wet weight vs dry weight
Most calculators return dry weight. Fresh harvested flower loses water during drying and curing. A common rule is that dry flower weight is about 20% to 25% of wet weight. If a calculator asks for wet weight, convert before you compare results.
Grams per watt benchmarks
Indoor growers use grams per watt as a shorthand. Values below 0.5 g/W are common for first runs. 1.0 g/W is a solid target for a dialed room. Values above 1.5 g/W require high light intensity, good climate control, and consistent genetics. These are benchmarks, not standards.
What the calculator cannot tell you
No calculator knows your cultivar, canopy shape, or pest pressure. It cannot predict THC or CBD content. It cannot replace a dry room scale. Use the estimate for planning jars, bags, and cure space, then replace it with measured harvest data.
Legal note
Federal hemp law sets a 0.3% THC limit on a dry weight basis. State rules for cannabis and hemp differ. Check your state before you grow.