What the percentage means#
A THC percentage is the share of the product's weight that is THC, as measured in a lab. For dried flower, 20% means 200 mg of THC in every gram. It does not tell you how strong one puff or one bite will feel, because that depends on how much you use and how you take it.
CBD is listed the same way. CBD is not intoxicating in the same way as THC, but the figure still matters, because it changes the balance of the product.
THCA is not the same as THC#
Many lab reports list THCA alongside THC. THCA is the acidic form found in the raw plant. Heat converts it to THC, so smoking, vaping or cooking with a product gives a different amount from the raw number. Many reports therefore show a total THC figure, often calculated as THC plus 0.877 times THCA.
When you compare two products, check the total THC figure rather than the THC line alone.
Work out milligrams per serving#
Multiply the percentage by the weight. A one gram pack at 20% THC contains about 200 mg. For an edible, the label should state mg per pack and mg per serving. Divide the total by the number of servings to find the dose per portion.
Write the figure down before you buy, and keep the pack in the same place at home so you do not confuse it with another product.
Read the lab report#
A certificate of analysis shows the tested THC and CBD, the batch number, the testing date and the lab's name. It may also show checks for moisture, heavy metals, pesticides and microbes. A shop that cannot show you a report is asking you to trust its word alone.
Check that the batch matches the pack and that the date is recent. An old report describes old product.
What the numbers cannot tell you#
Numbers do not capture how a product will feel for you. Your body, your tolerance, what you ate, your sleep and your mood all change the result. A high percentage is not automatically a better product, and a low one is not automatically safer.
Start with a small amount, learn the pattern and then decide. This guide is general information, not medical advice. If you have a health question, talk to a licensed practitioner.
Compare like with like#
When you compare two products, put them on the same basis. Look at the milligrams per serving, the serving size, and whether each number is for the whole pack or one unit. A product that looks stronger on the percentage may give a smaller dose per gram if it is measured differently.
Write the numbers in your notes app before you buy. It takes a minute, and it keeps the comparison honest when a menu uses a different unit from the label on the pack.
Check the unit and the serving#
Check the measurement unit. Some menus list percentage by weight, some list milligrams per pack and some list milligrams per unit. Before you compare, convert everything to the same unit, so a small pack and a large pack can be judged fairly.
Watch the serving size. A product may list a total milligram count for the whole pack and a serving size that is only a fraction of it. Dividing the total by the number of servings tells you the number you will actually take, and that is the figure to compare.
Expect labels to differ. Labels are written by different producers under different systems, so the same product can show different numbers on two packs. Treat the printed numbers as a guide and use your own log to see how a product suits you over time.
Keep the label with the product. If you need to compare later, or show a doctor or a shop what you took, the printed label and batch number are the fastest way to explain what the product was.