The most recent number from DEA being repeated on local news websites is 1.8mg of fentanyl hydrochloride per pill (up from 1.1mg a couple years earlier).
This matches roughly to my subjective understanding of the strength. They give a range of fentanyl being 80-100x the strength of morphine, which is 2.5x the strength of heroin, so we're talking 32-40x. Multiplying 36, the median, by 1.8 gives us 64.8mg -- exactly one grain! -- of diacetylmorphine. If the black tar heroin I get is ~45% pure (as I estimate), injecting one pill = 144mg tar.
Instead of injecting the usual 0.25g of tar, I mixed 0.125g with one (wheel-filtered) pill, and the intensity was comparable to my usual shot (though the legs were shorter of course). Chasing the pills on foil, I figure that with good technique you probably recover 50% of the active drug, possibly less. FWIW, when I've smoked them, it's felt like I was getting about half.