One scale for different opioids
Opioid pain medicines differ widely in strength: 10 mg of hydromorphone does far more than 10 mg of codeine. To judge a patient’s total exposure, prescribers convert each drug to its equivalent dose of oral morphine and add them up. The result, in morphine milligram equivalents per day (MME/day), appears in prescribing guidelines and in many state prescription monitoring programs.
The calculation
MME/day = dose × doses per day × conversion factor
For a fentanyl patch, the dose is in micrograms per hour and the patch counts once per day.
Conversion factors used by the CDC (2022 guideline):
| Opioid | Factor |
|---|---|
| Codeine | 0.15 |
| Tramadol | 0.2 |
| Tapentadol | 0.4 |
| Morphine | 1 |
| Hydrocodone | 1 |
| Oxycodone | 1.5 |
| Oxymorphone | 3 |
| Methadone | 4.7 |
| Hydromorphone | 5 |
| Fentanyl patch (per µg/h) | 2.4 |
Worked example
A patient takes oxycodone 10 mg three times a day and tramadol 50 mg twice a day:
- Oxycodone: 10 × 3 × 1.5 = 45 MME/day.
- Tramadol: 50 × 2 × 0.2 = 20 MME/day.
- Total: 65 MME/day.
What the total means
The risk of overdose rises with the daily dose. The CDC’s 2022 guideline no longer sets hard limits. It notes that the benefits of higher doses often level off while the risks keep rising, so any increase to 50 MME/day or more deserves careful reassessment, and increases toward 90 MME/day or more need strong justification. Combining opioids with benzodiazepines, alcohol or sleep medicines, sleep apnea, kidney or liver disease and older age raise the risk further at any dose.
Naloxone, which reverses opioid overdose, is available over the counter as a nasal spray in the United States. Prescribers are encouraged to offer it, especially at higher doses.
What the numbers are not
- Not a switching tool. Patients are not fully cross-tolerant, so when changing opioids, clinicians usually start the new drug 25 to 50% below the calculated equivalent.
- Methadone is tricky: its potency relative to morphine rises with the dose and it builds up over days. The single factor of 4.7 is for estimating exposure only.
- Fentanyl patches take 12 to 24 hours to reach steady levels and heat speeds up absorption.
- Buprenorphine is not counted in MME.
Never change an opioid dose or stop suddenly without your prescriber. If you or someone you know is struggling with opioid use, the SAMHSA helpline at 1-800-662-4357 is free and confidential, and the 988 Suicide and Crisis Lifeline is available by call or text.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.