⚠️ For healthcare professionals only
This tool is intended for use by licensed healthcare professionals (pharmacists, physicians, nurses, nurse practitioners) in clinical settings. Opioid conversions require clinical judgement, patient assessment and consideration of individual factors. Never use this tool as the sole basis for opioid prescribing decisions. Always apply a 25-50% dose reduction when rotating opioids to account for incomplete cross-tolerance. Verify all results with a clinical pharmacist or pain specialist.
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Opioid conversion calculator
Clinical Use OnlyFree
Calculate oral morphine equivalent (OME) daily dose and convert between opioids. Covers oral and transdermal formulations. A 25-50% dose reduction for incomplete cross-tolerance must be applied when rotating opioids.
mg/day
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Opioid conversion result
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Opioid equianalgesic conversions: the principles that matter
Equianalgesic tables give approximate dose ratios between opioids that produce equivalent analgesia. They're derived from single-dose studies in opioid-naive patients and are starting points, not precise prescriptions.
Incomplete cross-tolerance
When rotating between opioids, patients don't fully cross-tolerate. A patient tolerant to 60mg oral morphine per day will be more sensitive to an equianalgesic dose of oxycodone than you'd expect. The standard approach: calculate the equianalgesic dose, then reduce by 25-50% to account for this. Use the smaller reduction (25%) for patients with well-controlled pain, the larger reduction (50%) for frail, elderly or opioid-sensitive patients.
Fentanyl patch conversions
The fentanyl patch dose in mcg/hr represents a 72-hour delivery rate. A 25 mcg/hr patch delivers approximately 600 mcg over 72 hours. The commonly used conversion is: patch dose (mcg/hr) × 2.4 = approximate oral morphine equivalent (mg/day). This is a rough estimate. When converting to a patch from oral opioids, calculate the OME, reduce by 25-50%, then convert.
Methadone: the exception
Methadone conversions are not included in standard equianalgesic tables because the ratio varies dramatically with the dose of the current opioid. A patient on 30mg oral morphine per day has a very different methadone ratio than a patient on 300mg. Methadone initiation and conversion must be managed by a pain specialist or palliative care pharmacist. For renal impairment affecting opioid clearance, use our Renal Dose Adjustment Calculator. For weight-based dosing calculations, see the Weight-Based Dosage Calculator.
Frequently asked questions
OME (oral morphine equivalent) is a standardised way of expressing opioid doses. Every opioid dose is converted to the equivalent amount of oral morphine it would take to produce the same analgesic effect. OME is used to compare opioid loads across different drugs and routes, assess total daily opioid burden and guide safe rotation between opioids.
Opioid tolerance is partially opioid-specific. When you rotate to a different opioid, the patient doesn't have full tolerance to the new drug even if they're tolerant to the original. Giving a full equianalgesic dose risks overdose. The 25-50% reduction creates a safety margin. Pain can be titrated up if inadequate, but an overdose cannot be easily reversed.
Common indications include: intolerable side effects with the current opioid, inadequate analgesia despite dose escalation, renal or hepatic impairment affecting drug clearance, change in route of administration (e.g. oral to subcutaneous in end-of-life care), drug availability issues and specific clinical situations requiring a particular opioid's properties.