Opioid Conversion Calculator

Full opioid equianalgesic conversion calculator with cross-tolerance adjustment. Converts between oral and parenteral opioids using standard conversion ratios. Always reduce dose for cross-tolerance.

Select the current opioid being used.
mg/day or mcg/hr
Total daily dose of current opioid.
Select the opioid to convert to.
Reduce dose to account for incomplete cross-tolerance. If pain controlled, reduce 25-50%. If uncontrolled, may increase up to 25%.

Enter values and click Calculate to see results.

Note

Standard equianalgesic doses: Morphine oral 30mg = Morphine IV 10mg = Oxycodone oral 20mg = Hydromorphone oral 7.5mg = Hydromorphone IV 1.5mg = Fentanyl 0.2mg IV. Always round to available tablet strengths and provide breakthrough dosing.

Warnings & Limitations

  • NEVER convert to/from methadone without specialist consultation.
  • Methadone conversion is dose-dependent and NOT linear.
  • Cross-tolerance is incomplete - reduce converted dose by 25-50%.
  • Equianalgesic doses are estimates; individual variation is significant.
  • Meperidine is generally avoided due to neurotoxic metabolite (normeperidine).
  • Monitor closely after conversion - adverse effects can occur within 24 hours.
  • Fentanyl patches should only be used in opioid-tolerant patients.
  • Buprenorphine is a partial agonist with ceiling effect - conversion is complex.

References

  1. Opioid Equivalents and Conversions - Medscape — Medscape (2022)
  2. Dose equivalents and changing opioids - FPM — Faculty of Pain Medicine (2023)