💊

Opioid conversion calculator

Clinical Use Only Free

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
Opioid conversion result
Export:

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. The CDC Clinical Practice Guideline for Prescribing Opioids for Pain provides the current standard for opioid dosing and monitoring thresholds.

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. DURAGESIC's FDA prescribing information specifically warns that its own conversion tables must not be used in reverse, converting a patch dose back to another opioid with the same table overestimates the new opioid's dose and can cause fatal overdose, so patch-to-oral conversions deserve extra caution regardless of which formula is used.

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, which is a common reason to rotate away from methadone in the first place, use our Renal Dose Adjustment Calculator.

Confirming the tablet before you convert

An equianalgesic conversion is only as accurate as the identity and strength of the source medication. Confirming an unfamiliar or unlabeled opioid tablet before performing a conversion is a critical safety step, opioids from illicit sources can be counterfeit or contain fentanyl analogues far more potent than the imprint suggests. Use our Pill Identifier by Imprint to verify the specific product and strength first.

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.