In a legal marijuana market, edibles are dosed in milligrams. For those of us who would smoke a joint here and there, upon entry into the legalized reality, you suddenly have to grapple with this fact. Sure, we’ve been buying weed in some hybridized state between grams (metric) and ounces (imperial) for a while, yet the concept of how much weed you need for edibles comes down to differences in how we understand weight as a measure of effect.
In truth, seeing “10 milligrams” next to an edible is a poor indicator of how you will feel if the only other experience with marijuana you’ve had is smoking a joint with friends. To add to this, edibles can take significantly longer to kick in, so people often take too many too fast.

Edibles vs. Smoking

The process of eating edibles is often seen as a different experience than smoking. And down to a biochemical level, it definitely is. The high from edibles is produced through digestive metabolism rather than absorption through the lungs. This means it transitions through the digestive system, being broken down to get into the blood rather than going immediately to the bloodstream via absorption through the lungs.
Topical marijuana products, such as patches or salves, also skip this process of digestive metabolism because they are applied directly to the skin. The skin is, after all, an organ.

Do the Math

When it comes down to it, calculating how much weed you need for edibles requires two things. First, you have to know the recipe. Second, you have to understand how the effects manifest when absorbed through the digestive system. These two things will not only dictate how strong your edibles are, but they will also frame what you can expect to experience. Again, for those of us who are accustomed to smoking, vaping cannabis, or even using topical marijuana, those effects commonly happen sooner than with edibles. This, however, is not an understanding that translates to potency.

Potency, Percentages, and Perception

The potency of marijuana is commonly measured in percentages. If you are making edibles that you’re looking at in terms of milligrams, a conversion relating to potency percentages will have to be used before you can determine how much weed you need for edibles. It works like this:
As more and more states come online with medical or recreational marijuana programs, states are increasingly seeing it necessary to put the products through laboratory testing to determine (a) if harmful pesticides were used and (b) the potency of the cannabinoids and/or terpenes available in your weed or weed product. This made it easier for everyone to understand how strong the weed is, but when it comes to making edibles at home, a percentage indicating potency effectively undermines the fact that edibles are measured in milligrams.
This perception makes it difficult to determine how much you’ll actually need to make a potent batch. Compounded with the American aversion to using the metric system, the process of determining potency as a percentage of weight can easily produce an edible with either too much or not enough.

One gr am of marijuana is equal to 1,000 mg of marijuana.

On average, in a legal market, you’ll likely find your weed is between 10-20% THC. While this varies from plant to plant, the meaning of the percentage remains the same. If your plant shows a THC potency of 20%, this means 20% of the 1,000 mg is THC. Think about it like this:

1 gram = 1,000 milligrams
20% of 1,000 mg = 200 mg
Per one gram, you have 200 mg of THC
When determining how much weed you need for edibles, translating percentages to milligrams will help you understand how strong your batch is. The next part is knowing your recipe and how to cook with marijuana. If your recipe can make, say, 60 cookies, you now need to apply the milligram strength over that.
Wait, but how do you know how many milligrams you want per edible?

Bioavailability and First-Pass Metabolism

Research has shown THC can be processed through the digestive system, where a phenomenon known as first-pass metabolism is at work. First-pass metabolism is how your body converts food or drugs into things that impact your health and wellbeing. From food, this means getting necessary nutrients into the bloodstream. For drugs, this means getting a drug into the bloodstream. Typically, this process of first pass metabolism limits how much of a substance is absorbed into the blood. This is known as bioavailability.
Research suggests the bioavailability of smoking weed means your body will absorb an average of 30% if you smoke it. Think about it like this:

1 gram = 1,000 mg
20% THC = 200 mg per gram
30% of 200 mg = 60 mg
In effect, this means per gram of marijuana you smoke, your body may only fully absorb 6% of it, which is 30% of the available THC. When to comes to how much weed you need for edibles, the bioavailability of THC via the digestive system is commonly less. Yet, marijuana edibles are effective at 5 mg or 10 mg intervals, and even less if you see fit. So what is truly going on?

A Metabolite That Bends the Rule

THC, when taken through the digestive system, is more likely to be converted to a metabolite in the liver, which has an amplified availability in the blood. THC is mostly converted to 11-OH-THC in the liver, which research suggests is four times as available to the body, even with a lower bioavailability than when smoked (estimated between 6-10%). Think about it like this:

1 gram = 1,000 mg
20% THC = 200 mg THC
6% of 200 mg = 12 mg
12 *4 = 48 mg
In effect, when determining how much weed you need for edibles, this is the reason they feel more intense while having a lesser potency. This means for every 12 mg of edibles you consume, you can expect it to produce a biological effect equivalent to 48 mg, which is only 20% less than the effect you’d expect from smoking an entire gram.
Based on this, subjective factors are how strong you want your experience to be and how many edibles you’d like to make. Those are up to you to decide.