MME Calculator
Morphine Milligram Equivalents — CDC 2022 Conversion Factors
Enter the dose in mg per administration
Concurrent benzodiazepine use significantly increases overdose risk at any MME level
Calculate Morphine Milligram Equivalents
Select an opioid, enter the dose and frequency, then click Calculate to see total daily MME, overdose risk level, and a detailed breakdown.
How to Use the MME Calculator
Choose Your Calculator Mode
Select MME Total mode to calculate the combined daily MME from up to three concurrent opioids (e.g., a patient on both scheduled morphine and breakthrough oxycodone). Select Opioid Conversion mode when you need to rotate a patient from their current opioid regimen to a different opioid, and want to calculate a safe starting dose in the new opioid.
Enter Opioid, Dose, and Frequency
Select the opioid from the dropdown. Enter the dose per administration in milligrams (or mcg/hr for fentanyl transdermal and buprenorphine transdermal patches). Select the dosing frequency — q4h through q24h for scheduled dosing, q48h or q72h for extended-interval drugs, or TDD if entering a pre-calculated total daily dose. For multiple opioids, click Add Another Opioid and repeat.
Set Conversion Options (Conversion Mode)
In Opioid Conversion mode, select the target opioid you wish to convert to. Choose a cross-tolerance reduction percentage — the standard clinical recommendation is 25-50% to account for incomplete cross-tolerance when rotating opioids. A 50% reduction is conservative and appropriate for elderly patients or those with high comorbidity burden. Also check the benzodiazepine co-prescription box if the patient is concurrently taking any benzodiazepine.
Review Results and Clinical Recommendations
The calculator displays the total daily MME, overdose risk tier with clinical context, step-by-step calculation breakdown, naloxone recommendation if triggered at 50 MME/day or above, any special drug warnings for methadone or fentanyl, and (in conversion mode) the recommended starting dose in the target opioid. Use the print button to generate a print-friendly summary for patient records.
Frequently Asked Questions
What is the difference between MME, MED, and OME?
Morphine Milligram Equivalents (MME), Morphine Equivalent Dose (MED), and Oral Morphine Equivalent (OME) are all terms for the same fundamental concept: expressing any opioid dose as the equivalent amount of oral morphine. The different names reflect terminology used by different organizations. The CDC primarily uses MME, state PDMPs often use MED, and some international clinical guidelines use OME. This calculator uses the CDC 2022 conversion factors, which are the standard for US clinical practice. The numerical result is the same regardless of which term is used, as they all anchor to oral morphine as the reference with a factor of 1.0.
Why is my MME for fentanyl patch so high?
Fentanyl transdermal patches are extremely potent — approximately 100 times more potent than morphine by weight. The CDC 2022 conversion factor for fentanyl transdermal is 2.4 per mcg/hr. This means a 25 mcg/hr patch equals approximately 60 MME per day (25 × 2.4 = 60), a 50 mcg/hr patch equals approximately 120 MME per day, and a 100 mcg/hr patch equals approximately 240 MME per day. These numbers are accurate and reflect the very high potency of this medication. A 100 mcg/hr fentanyl patch is well above the CDC 120 MME/day threshold associated with 8.9x higher overdose risk. The factor of 2.4 already accounts for the 72-hour patch delivery cycle, converting the hourly rate to a daily morphine equivalent.
Can I use this calculator to convert between any two opioids?
The calculator supports conversion between most opioids on the list using the standard equianalgesic approach. However, several important limitations apply. Converting to or from methadone should always involve specialist consultation because methadone's conversion ratio is non-linear and dose-dependent — a calculated dose may be dangerously inaccurate. Converting to buprenorphine (for pain, not OUD treatment) requires careful clinical assessment. The calculated result in Conversion mode represents a starting dose estimate after cross-tolerance reduction — it should never be interpreted as an exact equianalgesic dose or used without clinical adjustment. Clinical guidelines universally recommend close monitoring when initiating a new opioid after rotation.
What does the incomplete cross-tolerance reduction mean?
When a patient develops tolerance to one opioid, that tolerance does not fully transfer to a different opioid. This phenomenon, called incomplete cross-tolerance, means patients are more sensitive to a new opioid than the equianalgesic calculation would suggest. If you simply converted a patient's full morphine dose to oxycodone, they would likely be overdosed because they would respond to a smaller oxycodone dose than calculated. Clinical guidelines recommend reducing the calculated equianalgesic dose by 25-50% when rotating opioids. Use 25% reduction when switching due to inadequate pain control (the patient still needs near-full pain coverage). Use 50% reduction as the standard approach for most rotations, and consider 50-75% in elderly patients, those with severe comorbidities, or in cases of concern for high sensitivity.
Why does this calculator show a warning for methadone?
Methadone is one of the most dangerous opioids from a prescribing safety perspective, with multiple unique properties that make standard MME conversion highly unreliable. Its half-life ranges from 8 to 59 hours and is highly variable between individuals, making it easy to accumulate to toxic levels. Its analgesic duration (4-8 hours) is much shorter than its half-life, leading some providers to incorrectly dose it more frequently. It causes QTc interval prolongation, creating cardiac arrhythmia risk — baseline and follow-up ECG monitoring is required. Its conversion ratio from morphine equivalents is non-linear: at low doses a 4:1 morphine-to-methadone ratio applies, but at very high morphine equivalent doses the ratio can exceed 20:1. The CDC uses a simplified fixed factor of 4.7 for surveillance purposes, which is not appropriate for clinical dose conversion.
When should I consider co-prescribing naloxone for a patient on opioids?
The CDC 2022 guideline recommends offering naloxone to patients receiving opioid therapy who are at increased risk of opioid overdose. This includes patients on 50 MME/day or higher (as calculated by this tool), patients who concurrently use benzodiazepines or other CNS depressants, patients with sleep apnea or other respiratory conditions, patients with a history of substance use disorder, patients who have experienced a prior overdose, and patients who live alone or have limited emergency access. Naloxone is safe to prescribe and is available as nasal spray (Narcan) or auto-injector (Evzio). When prescribing naloxone, educate both the patient and their household members or caregivers on how and when to use it. Naloxone access and education should be considered a routine part of opioid prescribing at higher doses.