Indoor Yield-O-Rama

Checking the Efficacy of the 25% Fresh-to-Dry Weight Conversion Value
When Employing a Range of Drying Practices

In September 2000 an interim check was performed using YOR records from growers who supplied both fresh and dry weights for their manicured harvests. This check was done to see how close the average percent of dry weight actually was to the 25% conversion value being used to convert fresh weight to dry weight, and if the range of dryness reported by growers fell between the low 20% shake-threat and the high 30% mold-threat thresholds. The corrected conv% is what the conversion value should have been, on average, to produce the actual dry weight from the fresh weight.

September 2000
Interim Check Results
Average Conversion Value 25%
Low 21%
High 32%


After the YOR collected it's last contribution in October 2002 a final check was performed, six new records qualified and were added to the list used for the interim check. Again, the corrected conv% is what the conversion value should have been to produce the actual dry weight from the fresh weight. For your convenience the conversion formula is highlighted in the table below. Notice how the YOR's calculated dry weight figure can easily be reconverted back to fresh weight by multiplying it by 4, but when a harvest is dried and reported only as actual dry weight the varying degrees of dryness make it impossible to know what the fresh weight was.

October 2002
Final Check Results
(weights are grams per square foot)
fresh weight X conv% = c weight
calculated dry weight
d weight
actual dry weight
4 A 90.8 25% 22.7 28.7 32%
102 B 133.2 25% 33.3 33.4 25%
106 C 165.6 25% 41.4 42.8 26%
116 D 137.2 25% 34.3 29.4 21%
136 E 178.0 25% 44.5 37.9 21%
145 E 156.0 25% 39.0 34.0 22%
147 E 145.2 25% 36.3 34.0 23%
160 E 173.2 25% 43.3 32.6 19%
164 E 182.0 25% 45.5 37.8 21%
166 F 112.4 25% 28.1 24.9 22%
169 E 200.8 25% 50.2 45.3 23%
171 E 167.2 25% 41.8 37.1 22%
grower corrected
A 32%
B 25%
C 26%
D 21%
E 22%
F 22%
Average 25%

Because the idea of collecting this data is to see how cannabis harvests are dried by a community of different growers and what their individual drying preferences are, we have to be careful not to let one grower's preference overpower the rest by appearing too many times in the list. If that were to happen, the community's average could be unfairly biased by one of its member's unique drying preferences. The average for the 7 records from grower-E is 22%. If we then use one unique figure for each grower, and use 22% to represent the average drying preference of grower-E, we get the following results.

The following table sums up the YOR's final findings for all growers who've reported both fresh and dry weights. As you can see, the originally estimated threshold range has widened from 20%-30% to 19%-32%, thus further increasing the potential for errors from reporting actual dry weight. Over the long term, however, the average degree of dryness reported by growers did in fact turn out to be 25% of the fresh weight.

YOR Summary corrected
Average Conversion Value 25%
Low 19%
High 32%


To top things off, data from an independent source unrelated to the YOR was also analyzed. While promoting products, fresh and dry weights for six crops were publicized by the makers of Advanced Nutrients during 2003, thus giving us an opportunity to examine their drying practices.

Independent Source
(drying practices)
  Fresh Weight Dry Weight conv%
Crop 1 4331.8 967.50 22%
Crop 2 2543.9 591.75 23%
Crop 3 2217.7 628.87 28%
Crop 4 1737.1 457.80 26%
Crop 5 1740.6 502.80 29%
Crop 6 1327.0 379.12 29%
Short Term Average

As you've probably noticed, because of the diverse drying practices used by different growers the true conversion value is a constantly moving target, with the short term average rising above or falling below 25% as each new reported yield is added to a list.


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