Opioid Conversion Calculator (MME)
Select a source opioid and enter its total daily dose to calculate morphine milligram equivalents (MME) and the equianalgesic dose for any target opioid. Conversion factors follow the 2022 CDC Clinical Practice Guideline. The tool also shows your MME risk tier (low, moderate, or high) against the CDC prescribing thresholds of 50 and 90 MME per day. This calculator is for clinical reference only - always apply clinical judgment and a 25-50% dose reduction when rotating between opioids.
What is an opioid conversion and why does it matter?
Opioid conversion (also called opioid rotation or equianalgesic dosing) is the process of switching a patient from one opioid to another while maintaining equivalent pain control. Clinicians perform conversions when a patient develops intolerable side effects to a current opioid, develops tolerance, or requires a route change (for example, from oral to intravenous). Because different opioids bind pain receptors with different potencies, a direct milligram-for-milligram switch would produce either under-dosing or, more dangerously, an overdose. Conversion tables give approximate equianalgesic doses - the amount of the new drug needed to produce the same analgesic effect as the dose of the original drug.
What are Morphine Milligram Equivalents (MME)?
Morphine Milligram Equivalents (MME), sometimes called Oral Morphine Equivalents (OME) or Morphine Equivalent Dose (MED), express any opioid dose as if it were oral morphine. Oral morphine is the reference standard: 1 mg oral morphine = 1 MME. Every other opioid and route has a conversion factor that translates it to this common currency. For example, oxycodone is 1.5 times as potent as oral morphine, so 20 mg of oxycodone = 30 MME. This common scale lets clinicians compare different drugs and sum up all opioids a patient takes into a single daily MME total. The CDC uses total daily MME to set safety thresholds: prescribing guidelines recommend caution above 50 MME/day and avoiding doses above 90 MME/day without compelling justification.
Incomplete cross-tolerance and why you must reduce the dose
When a patient is tolerant to one opioid, they are not fully tolerant to a different opioid - this is called incomplete cross-tolerance. The equianalgesic table gives the mathematically equivalent dose, but tolerance to the analgesic effects does not transfer completely between opioids. Starting at the full equianalgesic dose of the new drug therefore risks overdose, because the patient is naive to the new drug in terms of respiratory depression even while tolerant to the old one for pain relief. Standard practice is to reduce the calculated equianalgesic dose by 25-50% when starting the new opioid, then titrate upward based on response. A 50% reduction is preferred in elderly patients, those with organ impairment, or when the calculated dose is already above 90 MME/day.
Special considerations for methadone and transdermal fentanyl
Methadone is the most complex opioid to convert because its half-life is highly variable (8-59 hours), it accumulates over days to weeks, and the equianalgesic ratio is not fixed - it increases as the total dose increases. Many experts avoid converting to methadone using a simple table and instead use specialist guidance. Transdermal fentanyl patches create a subcutaneous drug depot that continues releasing drug for 12-24 hours after patch removal. When converting away from a fentanyl patch, clinicians must account for this continued absorption and delay the first dose of the new opioid accordingly. Both drugs should generally be managed by or in consultation with a pain specialist or palliative care team.
CDC 2022 Opioid MME Conversion Factors
| Opioid | Route | Dose unit | MME conversion factor |
|---|---|---|---|
| Codeine | Oral | mg/day | 0.15 |
| Fentanyl | Transdermal patch | mcg/hr | 2.4 |
| Fentanyl | IV/SC | mg/day | 300 |
| Hydrocodone | Oral | mg/day | 1.0 |
| Hydromorphone | Oral | mg/day | 5.0 |
| Hydromorphone | IV/SC | mg/day | 20.0 |
| Methadone | Oral | mg/day | 4.7 |
| Morphine | Oral | mg/day | 1.0 |
| Morphine | IV/SC | mg/day | 3.0 |
| Oxycodone | Oral | mg/day | 1.5 |
| Oxymorphone | Oral | mg/day | 3.0 |
| Tapentadol | Oral | mg/day | 0.4 |
| Tramadol | Oral | mg/day | 0.2 |
| Buprenorphine | Transdermal patch | mcg/hr | 12.6 |
Conversion factors from the 2022 CDC Clinical Practice Guideline for Prescribing Opioids for Pain. Multiply the total daily dose in the listed unit by the factor to get MME/day.
Frequently asked questions
What is the 50 MME/day threshold and why does it matter?
The 2022 CDC Clinical Practice Guideline for Prescribing Opioids for Pain recommends that clinicians carefully reassess before prescribing above 50 MME per day, and avoid prescribing 90 MME per day or more except in carefully evaluated and documented circumstances. These thresholds reflect the dose ranges at which data show meaningfully increased risk of opioid-related overdose and death. They are not absolute contraindications but serve as decision points for enhanced monitoring, non-opioid adjuncts, and specialist consultation.
Are these conversion factors exact?
No. Published equianalgesic ratios, including the CDC 2022 figures, are population-level estimates derived from clinical trials. Individual variation in opioid metabolism (influenced by genetics, organ function, age, and concurrent medications), receptor tolerance, and pharmacokinetics means that the actual equianalgesic dose for any given patient may be substantially different. Treat table-derived values as starting points and titrate based on clinical response.
Can I use this calculator to convert to methadone?
The calculator provides a mathematical estimate using a fixed conversion factor for methadone, but this should not be used as the sole basis for clinical prescribing. Methadone conversion is uniquely complex due to its variable and long half-life, high protein binding, accumulation risk, and dose-dependent equianalgesic ratio. Many guidelines recommend that conversions to methadone be performed only by clinicians with specific expertise in methadone prescribing, and that the conversion be done in stages with close monitoring.
How do I convert a fentanyl patch dose?
Enter the patch strength in micrograms per hour (mcg/hr). For example, a 25 mcg/hr fentanyl patch gives 25 x 2.4 = 60 MME/day. The 2.4 factor is from the 2022 CDC guideline. Note that when switching from a patch to a different opioid, the depot effect means the fentanyl continues to absorb for up to 24 hours after removal, so the first dose of the new drug should be delayed or reduced accordingly.
Why is buprenorphine handled differently in some calculators?
Buprenorphine is a partial opioid agonist with a ceiling effect on respiratory depression, which gives it a different risk profile from full agonists like morphine or oxycodone. MDCalc, for instance, excludes buprenorphine from its MME calculator for this reason. The conversion factor used here for transdermal buprenorphine (12.6 per mcg/hr) is a published equianalgesic estimate and should be applied with particular caution. Buprenorphine for opioid use disorder (Suboxone) is handled differently and is not addressed by this calculator.
Does this calculator apply to children?
No. This calculator uses adult conversion factors and is not validated for pediatric patients. Opioid dosing in children involves weight-based calculations, different pharmacokinetics, and age-specific considerations. Pediatric opioid prescribing should always be managed by appropriately trained clinicians.