Opioid to Morphine Equivalent (MME) Calculator
Estimate total daily morphine milligram equivalents (MME/day) and approximate conversion to another opioid. This tool is for educational reference only.
What this morphine conversion calculator does
This calculator helps you estimate how one opioid regimen compares to another using morphine milligram equivalents (MME). The process works in two steps: first, your current dose is converted to MME/day; second, that MME is converted into an estimated dose of a different opioid.
MME is useful because it gives clinicians and patients a common language for comparing opioid potency. For example, 20 mg/day of one opioid might produce a similar analgesic effect to 30 mg/day of another opioid. MME makes that relationship easier to estimate.
How to use the calculator
- Select the current opioid.
- Enter the current total daily dose in the correct unit shown under the input.
- Select the target opioid you want to compare with.
- Choose an optional cross-tolerance reduction percentage.
- Click Calculate Conversion.
The result displays your estimated MME/day, the direct calculated equivalent in the target opioid, and a reduced starting estimate based on the reduction percentage you selected.
Common conversion factors used in this tool
The following factors are approximate and based on commonly referenced opioid conversion tables. They represent estimated MME generated by one unit of each opioid per day.
| Opioid | Input Unit | MME Conversion Factor |
|---|---|---|
| Morphine (oral) | mg/day | 1 |
| Oxycodone (oral) | mg/day | 1.5 |
| Hydrocodone (oral) | mg/day | 1 |
| Hydromorphone (oral) | mg/day | 4 |
| Oxymorphone (oral) | mg/day | 3 |
| Codeine (oral) | mg/day | 0.15 |
| Tramadol (oral) | mg/day | 0.1 |
| Tapentadol (oral) | mg/day | 0.4 |
| Fentanyl patch (transdermal) | mcg/hr | 2.4 (MME/day per mcg/hr) |
Why cross-tolerance reduction matters
Two opioids may look equivalent on paper but still behave differently in a real patient. This is called incomplete cross-tolerance. When rotating from one opioid to another, many clinicians start below the mathematically equivalent dose and then titrate carefully.
Typical reduction ranges
- 25%: commonly used when pain is severe and close follow-up is available.
- 33%: a moderate reduction for many non-urgent opioid switches.
- 50%: often considered for frail patients, older adults, or situations with higher uncertainty.
Clinical cautions and limitations
No single calculator can replace clinical judgment. Conversion factors differ across sources, and several opioids have nonlinear or formulation-specific behavior. Methadone, buprenorphine, and some rapid formulation changes are intentionally not included in this simple tool.
- Assess sedation risk, respiratory status, and comorbidities before changing doses.
- Review renal and hepatic function because clearance differences can be substantial.
- Reassess frequently after conversion, especially in the first 24 to 72 hours.
- Consider non-opioid options and multimodal pain strategies whenever possible.
FAQ
Is MME a perfect predictor of overdose risk?
No. MME is a rough risk marker and comparison tool, not an absolute predictor.
Can I use this calculator for self-medication decisions?
No. Opioid adjustments should be made only with licensed medical supervision.
Why do fentanyl patch units look different?
Transdermal fentanyl is prescribed in mcg/hr, not mg/day, so the calculator uses patch-specific conversion logic and unit display.
Bottom line
A morphine conversion calculator is useful for quick estimation and communication, but safe opioid rotation still requires patient-specific assessment. Use these values as a starting point for discussion with a pain specialist, pharmacist, or prescribing clinician.