Here is a newer (as of this post)
Opioid Conversion Calculator (same disclaimers apply) developed by three pain experts, based on latest up-to-datest medical evidence, for
Practical Pain Management (
PPM).
The first link is the introductory article that discusses conversions (tables, calculators) in general and this new one specifically, including background information, safety concerns, and special cases like
methadone. I encourage everyone to read it before jumping to the calculator (There
WILL be a
QUIZ! 
)
PPM Launches Online Opioid Calculator
Thereafter, the direct link is:
Opioid Calculator
Doc