Converts the daily dose of the current opioid to oral morphine equivalents and suggests a starting dose of the new drug. Do not convert methadone with this tool.

Current opioidTotal daily dose (or µg per hour for a patch)New opioid (optional)

Reduction for incomplete cross-tolerance25%33%50%Usually 25 to 50%; reduce more in older adults, renal impairment or controlled pain.

This calculator needs JavaScript; the formula and its interpretation are in the text of this page.

An aid for clinicians; it does not replace clinical judgement, local protocols or the drug label. Double-check every result before prescribing.

Conversion factors

Conversion factor to oral morphine mg per day

Opioid	Factor
Oral morphine	1
IV or subcutaneous morphine	3 (oral to IV ratio 2–3 to 1) ^[2]
Oxycodone	1.5 ^[1]
Oral hydromorphone	5 ^[1]
Tapentadol	0.4 ^[1]
Tramadol	0.2 ^[1]
Codeine	0.15 ^[1]
Pethidine (meperidine)	0.1 ^[1]
Fentanyl patch (µg per hour)	2.4 ^[1]

Do not convert methadone with a fixed factor; its ratio changes with dose, and switching to it should be supervised by a pain or palliative care specialist.

How to convert

1
Add up the total 24-hour dose
The regular opioid plus all rescue doses of the previous day.
2
Convert to oral morphine equivalents
Use the factor in the table ^[1].
3
Reduce by 25–50%
For incomplete cross-tolerance; reduce more in older adults, renal or hepatic impairment, or when pain is controlled.
4
Divide and prescribe rescue doses
Divide the daily dose into regular doses and prescribe a short-acting opioid of about 10–20% of the daily dose for breakthrough pain; adjust the regular dose every 24–48 hours based on rescue use ^[2].

Caution

Fentanyl patches are only for opioid-tolerant patients (at least 60 mg oral morphine per day) with stable pain; the effect starts 12–24 hours after application.
In renal impairment morphine, codeine, tramadol and pethidine have accumulating metabolites; pethidine is not recommended for chronic cancer pain ^[2].
The CDC factors were written for risk assessment in non-cancer pain and the CDC guideline excludes cancer pain; in cancer pain they are only a starting estimate ^[1].

References

2 references

Show all referencesClose the reference list

Numbers in the text, such as ^[1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.

1
CDC Clinical Practice Guideline for Prescribing Opioids for Pain - United States, 2022Dowell D, Ragan KR, Jones CM, et al · MMWR Recomm Rep · 2022;71:1-95
DOI PubMed Back to text: 1 2 3 4 5 6 7 8 9
2
Management of cancer pain in adult patients: ESMO Clinical Practice GuidelinesFallon M, Giusti R, Aielli F, et al · Ann Oncol · 2018;29:iv166-iv191
DOI PubMed Back to text: 1 2 3

This page is based on reputable scientific sources and was last updated on 27 October 2026. The content of this website is for educational and informational purposes only and does not replace consultation, diagnosis or treatment by a specialist physician. Consult your treating physician about any treatment decision.

Printed from the website; the full and up-to-date version: https://drdabiri.com/en/tools/opioid-conversion-calculator/

Opioid Conversion Calculator (Morphine Equivalents)

Conversion factors

How to convert

Add up the total 24-hour dose

Convert to oral morphine equivalents

Reduce by 25–50%

Divide and prescribe rescue doses

References

Related pages