Marijuana math: Converting percentage to milligrams in edibles

weed2-1The other day, I was talking with a mom about marijuana edibles and potency when she asked, “Ten milligrams of what?” Referring to the 10mg serving size on recreational edibles, she kept asking, “At what potency?”

It took me awhile, but after several minutes going back and forth, I finally figured out what she was asking and where the confusion was.

When we talk about potency of flower or concentrates, we talk in percentages. For example, XYZ Concentrate is 75% THC or ABC Bud is 12% THC. That’s the potency.

But when we talk about the potency of edibles, we talk in miligrams. For example, ZYX Brownie has 50 miligrams of THC.

So how do we go from percentage to milligrams? Let’s do the math.

An ounce of flower/bud is around 28 grams. That’s 28,000 miligrams. If it tests at 10% potency for THC, that’s approximately 2,800mg of THC in the entire ounce.

You likely won’t get the full benefit of those 2,800mg if you smoke that ounce, by the way. Smoking is the least efficient method of consuming cannabis because so much of the material is burned up.

Let’s say you turn that ounce into 4 grams of concentrate that tests at 70% potency for THC. That’s approximately 700 milligrams of THC in each gram (1,000mg) of concentrate.

That gram of concentrate is then mixed in with other ingredients and portioned out to make 70 edible servings each containing 10mg of THC.

So to answer that mom’s questions…

Ten milligrams of what? THC.

At what potency? 100%.

— Rx MaryJane (Teri Robnett)


Categories: Business & Industry, Education, Labs and Testing

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13 replies

  1. Great explanation. Thank you for a logical, Layman’s description of the math that goes into changing the mg. into percents. I have worked at a Marijuana shop for over two years and this is by far the best detailing of this information that I have been exposed to. You have no idea how awesome it is to see someone braking this down into a level that anyone can understand.


  2. Rx mary jane i need your mathematical skills to help verify my calculations. I have 3.5 grams of cbd rich flower and the label says it contains .52% thc. Did i do the math right when i got that each gram would contain .016 mg of thc. please help me figure this out i really want to know how much i can use and still stay under the limit allowed on a drug test.


  3. so if I were to pull out a bag of flower to prepare an edible for just me, how much would i weigh out gram wise to eat? say normal 12% thc flower. thank you


  4. Help!! If I buy the strain landrace and I got 7 grams and the thc % = 20-25% how much butter or oil can I make?

    I need about 50-100mg to affect me each dose and I only do it at night before bed for my anxiety.

    I am new to pot, only started last year and never experimented as a kid so I’m a huge noob!!

    Thanks for any help!!!!!!


    • At 20%, each gram should have 200mg of THC in it. You probably won’t extract it all when you make butter, depending on how efficient your process is. You will probably get about 1000mg out of those 7 grams. That would give you around 20 doses at 50mg each.


  5. So if i get a 500mg candy bar, drink etc. How much THC am i really getting? My math tells me that 500mg would equal 50% THC. Dont know if thats correct though.


    • If the candy bar was purchased from a dispensary and says there’s 500mg of THC in it, then there’s probably close to 500mg of THC in it. The percentage would depend on how big the candy bar is. If the candy bar weighs a total of 1000mg, and 500mg of it is THC, then 50% would be correct.


  6. Does the CBD percentage work the same as THC.
    I have a Hemp strain that is 12 % CBD, making a oil out of
    48 fl oz of oil to 28 grams of dry flower.
    What will be my CBD valve per gram or fl oz
    Thanks Doc


    • Percentage is percentage, no matter the cannabinoid. 28g of flower at 12% would be around 3,360mg CBD. However, I would have to test the oil to really be able to answer your question since we never see 100% efficiency in the extraction. There’s always something left behind in the waste.


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