Three numbers to look for
Total CBD, in mg: the amount of CBD in the whole bottle. Bottle volume, in mL: how much oil the bottle holds. Concentration, in mg/mL: the amount of CBD in each millilitre.
The comparison that matters
Divide total CBD by bottle volume. For example, 1,500 mg in 30 mL is 50 mg/mL. The same 1,500 mg in 15 mL is 100 mg/mL.
SOS Isolate labels express concentration as 5%, 10%, 20% and 30%. Across its 15 mL bottles, those correspond to 750, 1,500, 3,000 and 4,500 mg of CBD per bottle.
Strength is not a serving instruction
A concentration calculation describes the oil. Use the serving directions on the actual product label, and ask a pharmacist when comparing different strengths. Drop sizes are not a universal measurement.