Here's a guide for home cooks on how to determine THC dosage for weed-infused recipes.
First, identify the percentage of THC in the strain you’re cooking with. Most strains have about 10 percent THC. Strains that have 15-20 percent THC are above average, and those with 21 percent THC or higher are exceptionally strong. If you can’t find online plant breeding information or cannabinoid lab tests for the strain, estimate at 10 percent THC.
You are starting out with a quarter ounce of marijuana, that’s 7 grams. An eighth would be 3.5 grams. Every 1 gram of cannabis bud has 1,000mg of dry weight. If a strain has about 10% THC, ten percent of 1,000mg would be 100mg. So for cooking or baking at home, it is safe to assume that a gram of cannabis contains at least 100mg THC.
You do the math accordingly to find out how much THC per serving.
Take the amount of ground marijuana, convert it to milligrams and divide it by the recipe yield to determine a per-serving dose of THC. A starting dosage for beginners is 5 milligrams per serving (the Colorado-mandated serving size for marijuana-infused edibles is 10mg THC). Three grams of ground marijuana equals 300mg THC. 300mg divided by the recipe yield, (a classic cookie recipe makes 60 cookies) equals 5mg per cookie. If you want to be even more cautious with your at-home cannabutter cooking, 1.5 grams (150mg) marijuana divided into a 60-cookie recipe will yield 2.5mg a serving.
Some notes about edibles: If you eat cannabis with fatty and protein rich foods, the effects of marijuana last longer in the body. If you eat cannabis in sugary candy form, the high doesn’t last as long. After eating an edible, we recommend waiting 2 hours. If you don’t feel high enough, don’t consume another edible, eat something fatty instead to increase the effect of the marijuana. If you feel too high, we recommend drinking orange juice or fruit juice to raise your blood sugar.