UKMedCalc

For healthcare professionals. Educational tool only — not a medical device. Verify all results against the current BNF, NICE guidance and local policy, and apply clinical judgement.

ConversionsPain

Opioid Conversion & Morphine Milligram Equivalents (MME)

Calculates total daily morphine milligram equivalents (CDC 2022 factors) and unadjusted equianalgesic doses between oral opioids.

mg

Sum of all doses in 24 h. For a fentanyl patch, enter the strength in µg/h.

Enter the required values to see the result.

Formula

MME=daily dose (mg)×conversion factorTarget dose=MMEtarget factor\text{MME} = \text{daily dose (mg)} \times \text{conversion factor} \qquad \text{Target dose} = \frac{\text{MME}}{\text{target factor}}

Fentanyl patch: MME/day = patch strength (µg/h) × 2.4 (e.g. 25 µg/h = 60 MME/day). Methadone and buprenorphine are excluded — no accepted simple conversion factor.

Caveats & limitations

  • Equianalgesic ratios are approximate and vary between sources; individual response varies widely.
  • When switching opioids, reduce the calculated dose by 25–50% for incomplete cross-tolerance, then titrate.
  • Methadone and buprenorphine are excluded — seek specialist advice for these switches.
  • Do not use this tool to convert TO a fentanyl patch; use the BNF patch conversion guidance.
  • CDC 2022 updated the hydromorphone factor from 4 to 5 — older references differ.

Evidence & UK guidance

Primary evidence

  • Dowell D, Ragan KR, Jones CM, et al. CDC clinical practice guideline for prescribing opioids for pain — United States, 2022. MMWR Recomm Rep. 2022;71(RR-3):1–95.

    PubMedDOI

UK practice

The BNF palliative care section and UK formularies (e.g. the Palliative Care Formulary) publish equianalgesic ratios that differ slightly from CDC factors — e.g. oral morphine : subcutaneous diamorphine ≈ 3:1, and oral oxycodone ≈ 1.5–2× oral morphine. MME is a risk-stratification measure, not an equianalgesic switch table; for opioid switching in palliative care, follow the BNF/PCF and titrate.

Official resources

Formula and citations last verified: 2026-08-03

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