Opioid Conversion Calculator
Calculate morphine milligram equivalents (MME) and convert between 12 opioid formulations. Includes CDC risk thresholds, adjustable cross-tolerance dose reduction, methadone tiered conversion, and clinical guidance for safe opioid rotation.
Convert Opioid Dose
Select the source opioid, enter the dose and frequency, and choose a cross-tolerance reduction percentage. The calculator will display the daily morphine milligram equivalent (MME), CDC risk category, and equivalent doses for all other opioids with the selected dose reduction applied.
Opioid conversion calculations are estimates only. Equianalgesic ratios are derived from single-dose studies and may not apply accurately to chronic dosing, high doses, or individual patients. Incomplete cross-tolerance means patients switching opioids require dose reduction (typically 25–50%) from the calculated equivalent. Methadone conversion requires specialist expertise due to non-linear pharmacokinetics. All converted doses must be verified by a qualified clinician before administration.
Understanding Morphine Milligram Equivalents
The morphine milligram equivalent (MME) — also called oral morphine equivalent daily dose (OMEDD) — is a standardised metric that expresses any opioid dose as the equivalent dose of oral morphine. It provides a common language for comparing opioid exposure regardless of which agent is prescribed, enabling clinicians to assess total opioid burden, evaluate overdose risk, and comply with prescribing guidelines.
The MME is calculated by multiplying the dose of the opioid by its MME conversion factor — a ratio representing its analgesic potency relative to oral morphine. These factors were derived from single-dose equianalgesic studies, primarily in acute pain settings, and standardised by organisations including the CDC, CMS, and various national pain societies.
MME Calculation
Daily MME = Daily Dose × MME Factor
Example: Oxycodone 10 mg QDS (4×/day) = 40 mg/day × 1.5 = 60 MME/day
Cross-Opioid Conversion
Target Dose = Daily MME ÷ Target Factor
Example: 60 MME/day → Hydromorphone PO = 60 ÷ 4 = 15 mg/day. After 25% reduction: 11.25 mg/day
MME is a risk communication tool, not a clinical equivalence guarantee. The CDC uses MME thresholds (≥ 50, ≥ 90 MME/day) as markers of increasing overdose risk to guide prescribing decisions. However, a patient’s actual opioid tolerance, clinical context, and individual pharmacogenomics mean that two patients on the same MME may have very different clinical responses. MME should inform — not dictate — prescribing.
Equianalgesic Reference & Risk Thresholds
The following table provides the standard equianalgesic doses and MME conversion factors for commonly prescribed systemic opioids. All values are referenced to oral morphine 30 mg as the standard.
| Opioid | Route | Equianalgesic Dose | MME Factor |
|---|---|---|---|
| Morphine | PO | 30 mg | 1 |
| Morphine | IV / SC | 10 mg | 3 |
| Codeine | PO | 200 mg | 0.15 |
| Tramadol | PO | 150 mg* | 0.2 |
| Hydrocodone | PO | 30 mg | 1 |
| Oxycodone | PO | 20 mg | 1.5 |
| Hydromorphone | PO | 7.5 mg | 4 |
| Hydromorphone | IV / SC | 1.5 mg | 20 |
| Oxymorphone | PO | 10 mg | 3 |
| Tapentadol | PO | 75 mg | 0.4 |
| Fentanyl | TD patch | 12.5 mcg/hr** | 2.4 (per mcg/hr) |
| Methadone | PO | Variable*** | Variable |
* Tramadol equivalence is approximate; it has additional serotonergic and noradrenergic activity. ** Fentanyl patch dose is in mcg/hr (continuous delivery); MME/day = mcg/hr × 2.4. *** Methadone has a non-linear conversion ratio — see Methadone section below.
CDC MME Risk Thresholds
The CDC MME thresholds are intended to guide non-cancer chronic pain prescribing and should not be used as rigid ceilings that prevent adequate analgesia in cancer pain, palliative care, or sickle cell disease. The 2022 CDC Clinical Practice Guideline explicitly states that these recommendations do not apply to pain related to cancer treatment, palliative care, or end-of-life care.
Clinical Factors in Opioid Conversion
Converting between opioids is one of the highest-risk prescribing activities in medicine. The following clinical factors must be considered to ensure patient safety during opioid rotation.
When a patient switches from one opioid to another, tolerance to the original opioid does not fully transfer to the new one. This phenomenon — incomplete cross-tolerance — means that the calculated equianalgesic dose of the new opioid may produce a greater-than-expected effect, risking overdose. The mechanism relates to differences in receptor subtype selectivity, receptor binding kinetics, and active metabolite profiles between opioids.
The standard recommendation is to reduce the calculated equianalgesic dose of the new opioid by 25–50% to account for incomplete cross-tolerance. Greater reductions (50%) are recommended for elderly patients, those with renal or hepatic impairment, or when converting to methadone. Smaller reductions (25%) may be appropriate for younger patients with well-controlled pain. The reduced dose should be supplemented with breakthrough (PRN) dosing as needed, and then titrated upward based on clinical response.
- 25% reduction: standard for most opioid rotations
- 33% reduction: appropriate for moderate-risk patients
- 50% reduction: elderly, frail, renal/hepatic impairment, or converting to methadone
- 0% reduction: same opioid, route change only (e.g., morphine PO → IV)
Methadone is pharmacologically unique among opioids. It has a long and highly variable half-life (15–60 hours, sometimes longer), acts on NMDA receptors in addition to mu-opioid receptors, and exhibits non-linear equianalgesic ratios — meaning that the conversion ratio changes with the dose level. At low morphine-equivalent doses, the ratio is approximately 4:1 (morphine:methadone), but at high doses it may be 12:1 or even 20:1. Using a single fixed ratio across all dose levels risks fatal overdose.
The most widely used conversion guideline is the Ayonrinde (tiered) approach:
- Oral morphine ≤ 30 mg/day → ratio 2:1 → methadone ≤ 15 mg/day
- 31–99 mg/day → ratio 4:1
- 100–299 mg/day → ratio 8:1
- 300–499 mg/day → ratio 12:1
- 500–999 mg/day → ratio 15:1
- ≥ 1000 mg/day → ratio 20:1
After calculating the dose, apply an additional 25–50% reduction for incomplete cross-tolerance. Methadone conversion should only be performed by, or in consultation with, clinicians experienced in its use. Its long half-life means accumulation occurs over days — dose-related respiratory depression may not manifest until 3–5 days after initiation or dose increase.
Transdermal fentanyl has unique pharmacokinetics that complicate conversion. The patch creates a subcutaneous depot, with onset of action of 12–24 hours after application and a similar lag after removal. Steady-state plasma levels are typically reached after 2–3 patch applications (i.e., 6–9 days for a 72-hour patch). This means that dose changes take days to fully manifest, making rapid titration impossible and overdose from over-correction a delayed risk.
When converting TO a fentanyl patch, calculate the daily oral morphine equivalent, divide by 2.4 to get the mcg/hr patch dose, and round DOWN to the nearest available patch strength (12, 25, 37.5, 50, 75, or 100 mcg/hr). Provide immediate-release oral opioid for breakthrough pain during the first 12–24 hours while the patch reaches therapeutic levels. When converting FROM a patch, remember that significant fentanyl remains in the subcutaneous depot for 12–24 hours after removal — do not start full-dose oral opioid immediately.
Fentanyl patches should only be used in opioid-tolerant patients. The FDA defines opioid-tolerant as receiving at least: morphine 60 mg/day PO, oxycodone 30 mg/day, hydromorphone 8 mg/day, or an equianalgesic dose of another opioid for one week or longer.
Several opioids are prodrugs that require CYP2D6-mediated activation. Codeine is the most clinically significant example — it requires conversion to morphine by CYP2D6. Approximately 6–10% of Caucasians and 1–2% of East Asians are CYP2D6 poor metabolisers who derive little analgesic effect from codeine. Conversely, 1–2% of Caucasians and up to 29% of certain African populations are ultrarapid metabolisers who convert codeine to morphine excessively, risking respiratory depression. Several deaths have been reported in CYP2D6 ultrarapid metaboliser children given codeine post-tonsillectomy.
Tramadol is similarly CYP2D6-dependent for its active metabolite (O-desmethyltramadol). Oxycodone is partially metabolised by CYP2D6 to oxymorphone, though this pathway contributes less to overall analgesia. Hydromorphone, morphine, and fentanyl do not depend on CYP2D6 for activation and are safer choices when CYP2D6 status is unknown or abnormal.
Equianalgesic tables are often treated as symmetrical — if morphine 30 mg PO = oxycodone 20 mg PO, then the assumption is that oxycodone 20 mg PO = morphine 30 mg PO in the reverse direction. However, clinical evidence suggests that conversion ratios may not be perfectly bidirectional, particularly for agents with active metabolites or unique receptor profiles. Methadone is the most extreme example (its potency relative to morphine increases as the dose increases), but smaller asymmetries exist between other opioids.
When converting in either direction, the key safety principle remains the same: calculate the equianalgesic dose, apply a cross-tolerance reduction, provide breakthrough analgesia, and titrate to effect. The direction of conversion does not change the need for dose reduction, but clinicians should be aware that the “true” equianalgesic ratio in a specific patient may differ from the published population average.
Special Populations
Opioid conversion carries additional risk in populations where pharmacokinetics, pharmacodynamics, or vulnerability to adverse effects differ from the general adult population.
Concurrent CNS depressants dramatically increase risk. Benzodiazepines, gabapentinoids, muscle relaxants, sedating antihistamines, and alcohol all potentiate opioid-induced respiratory depression. When any of these are co-prescribed, the effective MME risk threshold is lower — consider reducing the opioid dose further and co-prescribing naloxone at any MME level.
Step-by-Step Approach to Opioid Rotation
Opioid rotation (switching from one opioid to another) is indicated when the current opioid produces inadequate analgesia despite dose escalation, intolerable side effects, or both. The following systematic approach minimises the risk of under- or over-dosing during the transition.
Sum all opioid intake over 24 hours, including scheduled doses and breakthrough (PRN) doses actually taken. If the patient is on multiple opioids simultaneously, convert each to its daily MME and sum them. If the patient uses a fentanyl patch plus an oral breakthrough opioid, include both in the total. Document the total daily dose in the original unit and as MME.
Multiply the total daily dose by the MME conversion factor for each opioid. If the patient is on multiple opioids, sum all MME values to get the total daily MME. This provides a standardised reference point for calculating the dose of the new opioid. Double-check the calculation — errors at this step propagate through the entire conversion.
Divide the total daily MME by the MME factor of the target opioid. This gives the theoretical equianalgesic daily dose of the new agent. For methadone, use the tiered conversion table rather than a single fixed ratio. For fentanyl patches, divide daily MME by 2.4 to get the mcg/hr patch strength.
Reduce the calculated equianalgesic dose by 25–50% to account for incomplete cross-tolerance. Choose the reduction percentage based on the patient’s risk profile: 25% for young, otherwise healthy patients with well-controlled pain; 50% for elderly, frail, or renally/hepatically impaired patients, or when converting to methadone. If pain has been poorly controlled (the reason for rotation), a smaller reduction (25%) is appropriate since the patient may need a relatively higher dose of the new agent. If the rotation is primarily due to side effects with adequate analgesia, a larger reduction (33–50%) is safer.
Divide the reduced total daily dose into the appropriate dosing intervals for the new opioid (e.g., q4h for immediate-release morphine, BD for modified-release preparations). Prescribe an immediate-release breakthrough dose of approximately 10–15% of the total daily dose, available every 1–2 hours PRN. Monitor closely for the first 48–72 hours, assessing pain control, sedation, and respiratory rate. Titrate the scheduled dose upward by 25–50% every 24–48 hours based on breakthrough use and clinical response.
The five-step approach: (1) total current daily dose → (2) convert to MME → (3) calculate new opioid equianalgesic dose → (4) reduce by 25–50% → (5) divide into doses + prescribe breakthrough. When in doubt, err on the side of caution — it is always safer to start lower and titrate up than to overshoot and cause respiratory depression.
Common Pitfalls & Limitations
The single most common cause of fatal opioid rotation errors is using the full calculated equianalgesic dose without applying a dose reduction. Equianalgesic ratios represent population averages from single-dose studies — they do not account for the fact that tolerance to one opioid does not fully transfer to another. Administering the full equianalgesic dose can cause respiratory depression, sedation, and death, especially with potent opioids like fentanyl, hydromorphone, or methadone.
How to avoid: Always apply at least a 25% reduction when rotating between different opioids. Use 50% for high-risk patients or when converting to methadone. The only exception is a same-opioid route change (e.g., morphine PO to morphine IV), where the known PO:IV ratio can be used directly.
Methadone’s equianalgesic ratio to morphine is not a fixed number — it changes with the total daily morphine-equivalent dose. At low doses (morphine ≤ 30 mg/day), the ratio may be 2:1 or 3:1, but at high doses (≥ 500 mg/day), the ratio may be 15:1 or 20:1. Using a single “average” ratio like 5:1 at all dose levels will under-dose patients at low morphine equivalents and catastrophically overdose patients at high morphine equivalents. Methadone’s long and variable half-life (15–60 hours) means that accumulation-related toxicity may not manifest for 3–5 days.
How to avoid: Always use a tiered conversion protocol. Involve a palliative care, pain medicine, or addiction medicine specialist whenever possible. Monitor the patient closely for at least 5–7 days after initiation or dose adjustment of methadone.
When calculating total daily opioid exposure, clinicians sometimes forget to include all sources. A patient may be receiving a fentanyl patch (basal), oral oxycodone for breakthrough, and codeine-containing cough syrup. All three contribute to the total MME and must be summed. Combination products (e.g., oxycodone/paracetamol, codeine/paracetamol) contain opioid that must be counted. In hospital, PCA (patient-controlled analgesia) use over 24 hours must be reviewed alongside any oral or patch opioid.
How to avoid: Perform a complete opioid reconciliation before any conversion. Check the medication administration record for scheduled and PRN opioid use. Include non-prescription codeine-containing products if the patient uses them. Sum all sources as MME before calculating the new opioid dose.
Fentanyl transdermal patches are contraindicated in opioid-naïve patients. The lowest available patch strength (12 mcg/hr) delivers approximately 30 MME/day — a dose that can cause fatal respiratory depression in a patient without opioid tolerance. Additionally, the depot nature of the patch means that if toxicity develops, removal of the patch does not result in immediate cessation of drug delivery — fentanyl continues to be absorbed from the subcutaneous depot for 12–24 hours.
How to avoid: Never prescribe a fentanyl patch as the first opioid. Patients must already be receiving and tolerating at least 60 mg/day of oral morphine equivalent (or equivalent) for one week before a patch is considered. If converting a patient to a fentanyl patch, use the calculator to confirm the MME warrants a patch and that the patient meets the opioid-tolerant definition.
The CDC’s MME risk thresholds (≥ 50, ≥ 90 MME/day) were developed for non-cancer chronic pain in primary care settings. Misapplying these thresholds to cancer pain, palliative care, or sickle cell disease patients has led to well-documented cases of undertreated pain, forced tapers causing withdrawal, and patient harm. The CDC 2022 guideline explicitly states that these recommendations do not apply to patients receiving cancer treatment, palliative care, or end-of-life care.
How to avoid: Always consider the clinical context when interpreting MME. In cancer and palliative care, pain should be treated to effectiveness regardless of the MME number, with appropriate safety monitoring. MME remains useful as a communication and risk-awareness tool, but should not be used as a prescribing ceiling in these populations.
Quick Reference Summary
for Cross-Tolerance
Lower Risk Threshold
Substantially Increased Risk
% of Total Daily Dose
| Clinical Scenario | Key Conversion Point |
|---|---|
| Morphine PO → IV | Divide by 3 (30 mg PO = 10 mg IV); no cross-tolerance reduction needed |
| Oxycodone PO → Morphine PO | Oxycodone × 1.5 = MME; then divide by 1 for morphine; reduce by 25% |
| Any opioid → Fentanyl patch | Daily MME ÷ 2.4 = mcg/hr patch; round DOWN; patient must be opioid-tolerant |
| Fentanyl patch → Oral morphine | mcg/hr × 2.4 = daily MME; reduce 25%; allow 12–24 hr washout before full oral dose |
| Any opioid → Methadone | Use tiered ratio (NOT a single fixed ratio); reduce 25–50%; specialist recommended |
| Opioid-naïve patient | Never use equianalgesic tables at face value; start at 25–50% of calculated dose |
The Golden Rule: Calculate the equianalgesic dose, then reduce it. It is always safer to under-dose and titrate up than to overshoot and treat respiratory depression. Every opioid rotation should have a plan for breakthrough analgesia and a follow-up assessment within 48–72 hours.
Disclaimer & References
For Educational Purposes Only. This calculator and the accompanying clinical information are intended as educational tools for healthcare professionals. They do not replace clinical judgement. Results should be interpreted in the full clinical context. Lab reference ranges vary by institution — verify with your own laboratory. Drug dosages should be confirmed against current prescribing information.
References
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- Fine PG, Portenoy RK. Establishing “best practices” for opioid rotation: conclusions of an expert panel. J Pain Symptom Manage. 2009;38(3):418-425. DOI: 10.1016/j.jpainsymman.2009.06.002
- Shaheen PE, Walsh D, Lasheen W, Davis MP, Lagman RL. Opioid equianalgesic tables: are they all equally dangerous? J Pain Symptom Manage. 2009;38(3):409-417. DOI: 10.1016/j.jpainsymman.2009.06.004
- Mercadante S, Caraceni A. Conversion ratios for opioid switching in the treatment of cancer pain: a systematic review. Palliat Med. 2011;25(5):504-515. DOI: 10.1177/0269216311406577
- Ayonrinde OT, Bridge DT. The rediscovery of methadone for cancer pain management. Med J Aust. 2000;173(10):536-540. DOI: 10.5694/j.1326-5377.2000.tb139324.x
- Webster LR, Fine PG. Review and critique of opioid rotation practices and associated risks of toxicity. Pain Med. 2012;13(4):562-570. DOI: 10.1111/j.1526-4637.2012.01357.x
- Brant JM, Keller L, McLeod K, Yeh C, Eaton LH. Has the time come to retire the equianalgesic table? Clin J Oncol Nurs. 2017;21(3):266-270. DOI: 10.1188/17.CJON.266-270
- Nielsen S, Degenhardt L, Hoban B, Gisev N. A synthesis of oral morphine equivalents (OME) for opioid utilisation studies. Pharmacoepidemiol Drug Saf. 2016;25(6):733-737. DOI: 10.1002/pds.3945