'A gram of fentanyl is around 50 times as powerful as pure heroin. Some fentanyl drugs are even stronger. Carfentanil, a drug associated with clusters of deadly overdoses, is estimated to be 100 times as strong as fentanyl itself, according to the Drug Enforcement Administration.'

https://www.nytimes.com/2023/10/05/upshot/fentanyl-opioids-mexico-explainer.html