Marijuana Math: Calculating milligrams per milliliter in liquids

Accurately converting percentage to milligrams per milliliter can be confusing, and it’s easy to get it wrong if you don’t factor in the density of the liquid suspension.

You know how oils typically float to the top when mixed in water, while other substances like honey sink to the bottom? That’s because their density and molecular weight are different. One is lighter and less dense, while the other is heavier and more dense.

In order to accurately calculate milligrams per milliliter, you’ll need the following information: Potency percentage, Density of the suspension, and Volume of the liquid.

Dosing Infused Oils

Let’s say you want to know how many mg are in a 50 ml bottle of ethanol tincture at 2% potency:

Potency Percentage = 2%
Density of ethanol* = 0.789 g/ml
Volume of liquid = 50 ml

Step One: Convert Density from g/ml to mg/ml:
0.789 x 1000 = 789 mg

Step Two: Multiply Density in mg/ml by Potency Percentage:
789 x 2% = 15.78 mg/ml

Step Three: Multiply mg/ml by Volume of liquid:
15.78 x 50 = 789 mg in 50 ml

For this example, let’s assume you’re putting .5 ml of infused MCT (liquid coconut oil) into capsules:

Potency Percentage = 3%
Density of MCT* = 0.955 g/ml
Volume of liquid = 0.5 ml

Step One: Convert density from g/ml to mg/ml:
0.955 x 1000 = 955 mg

Step Two: Multiply Density in mg/ml by Potency Percentage:
955 x 3% = 28.65 mg/ml

Step Three: Multiply mg/ml by Volume of liquid:
28.65 x 0.5 = 14.33 mg in 0.50 ml

Let’s say you’re planning to bake some edibles and want to know how many milligrams are in a tablespoon of butter with a potency of 0.5%.

Potency Percentage = .5%
Density of butter* = 0.911 g/ml
Volume of liquid = 15 ml (approximately 1 tablespoon)

Step One: Convert density from g/ml to mg/ml:
0.911 x 1000 = 911 mg

Step Two: Multiply Density in mg/ml by Potency Percentage:
911 x 0.5% = 4.56 mg/ml

Step Three: Multiply mg/ml by Volume of liquid:
4.56 x 15 = 68.4 mg in 15 ml (1 tbsp)

*Each suspension will have a different density. Here are some common ones.
Ethanol: .789 g/mL
Vegetable glycerin = 1.26 g/mL
Coconut oil = .926 g/mL
Olive oil = .915 g/mL
Safflower oil = .921 g/mL
Butter = .911 g/mL
MCT Oil = .955 g/mL
Honey = 1.43 g/mL
(Most oils have a density between 0.90 to 0.95)

Bring your infused oils to The Good Lab for a Cannabinoid Potency Profile. We can help you figure out the milligrams per milliliter. Contact us to schedule a time to drop off your sample.


10 thoughts on “Marijuana Math: Calculating milligrams per milliliter in liquids

  1. Gerald Marshall December 20, 2020 / 8:57 am

    I have a question. I Have cannabis oil that is 29.2 mg/ml, with a net content of 30ml. According to my calculations if I made brownies I would have to cut them into about 24 pieces to make each piece @ 32 mg of THC. Am I close/

    • Rx MaryJane January 15, 2021 / 1:03 pm

      These are my calculations:
      876mg/24=36.5mg per piece.

  2. Wild Gift January 10, 2021 / 3:36 pm

    Hi, I have some people telling me this math isn’t correct and now I’m extremely confused. My Remedy has tested at 13% CBD and I’ve infused 49 grams into 875ml of MCT oil. I calculated 124 mg CBD / ml of oil. Am I wrong?

    • Rx MaryJane February 25, 2021 / 1:21 pm

      49 grams = 49,000mg
      49000×13% = 6370mg CBD
      6370 / 875 = 7.28mg/ml CBD
      This assumes no loss during processing and doesn’t factor in any change in density of the MCT after infusing.
      The best way to know the potency for sure is to have it tested at a lab.

  3. Steven Baumann February 23, 2021 / 7:48 am

    I initially infused 2 Cups of 151 everclear with 14g of flower @ 20% potency, I recently made FECO and reduced 1 1/4 Cup and ended up with 4ml, how do I figure out the potency per each 1ml? Thanks

    • Rx MaryJane February 25, 2021 / 1:12 pm

      14g of flower at 20% would be 2800mg. (14000 x 20%) There was likely quite a bit of loss during the process, so you won’t end up with 2800mg in the final batch. The only way to know for sure is to have it tested at a lab.

  4. Katerina Gill March 24, 2021 / 1:52 pm

    So I got a CBD oil. All it says on the package is “Contents contains equivalent of 0.4g of dried cannabis. Total THC per activation is 1.5mg. Total CBD per activation 25mg. Organic MCT.” and the front says “Total THC 1.5mg/g, Total CBD 28.2mg/g”

    The bottle itself just says net weight 28.2g, doesn’t say how much fluid is in there.
    It comes with a dispenser that takes up to 1mL at a time, and is broken up into tenths for measurement.

    I’m assuming I can multiply 1.5mg times 28.2, to get 42.3mg of THC In the whole bottle I think? and 794.24mg of CBD?

    But I’m struggling with converting. For the life of me I can’t figure out how many mg of THC and CBD are in, say, 0.1mL and 0.5mL and 1mL of oil. And as someone who’s pretty sensitive and has to keep my doses small (3-5mg of THC at a time maximum, so pretty much nearly microdosing), it’s really important that I know what I can take 🙁

    • Rx MaryJane April 9, 2021 / 12:08 pm

      That sounds like a very confusing label. It looks like the assumptions for your math are right. Chances are this is in a standard 1-ounce dropper bottle, which is about 30ml, at a weight of 0.94g/ml. I get 1.4mg of THC and 26.5mg of CBD in 1ml of oil. You should be able to calculate more accurately from there. Good Luck!

  5. ediblemaker April 6, 2021 / 12:54 pm

    I’m just a little confused here. Can someone verify if my math is correct

    i have 1g of RSO at 68% THC in 100ml of MCT oil

    1g = 1000mg
    1000x 68% = 680 THC
    680 / 100ml = 6.8mg/ml THC

    • Rx MaryJane April 9, 2021 / 12:14 pm

      Your math is correct for figuring mg/g (68% = 680mg/g) Because RSO varies so much from batch to batch, I can’t answer the rest of your question. If you can tell me how much a milliliter of your RSO weighs, I might be able to help you more.

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