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.

 

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