[TwoBit]

That carfentanil looks like about a milligram, but impossible to say without knowing its density.

[Black101]

"The New York Times warns that a particle of carfentanil as small as a grain of salt or piece of dust can be deadly and that the drug is lethal in a dose as minuscule as 0.02 milligrams. "

so about 1/50th of a milligram is deadly... not sure what's the maximum dose before it kills you

[tpm]

1.0 µg of carfentanil is equivalent to 10 mg of morphine