For instance, a 0.45 gram joint of strong herbal cannabis might contain 12.78 standard THC units, while a weaker, seeded herbal cannabis can contain just 3.78 THC units, according to the new estimates.

The study's authors found that to reduce the risk of developing cannabis use disorder, adults should not exceed 8 THC units per week.

So you can smoke 2/3 of a good, but small, half gram joint, or just over two shitty joints a week.