Opioid Conversion Calculator: Morphine Equivalents (MME)
Convert between the common oral and IV opioids through oral morphine equivalents, with the incomplete cross-tolerance reduction applied and shown, the per-dose amounts spelled out, and a breakthrough dose suggested.
Equianalgesic tables disagree with each other, patients differ, and published factors are population averages. Every result on this page already includes a reduction for incomplete cross-tolerance, and it is still only a starting point. Reassess the patient after the first doses. This is educational content, not medical advice; institutional protocol and current references govern.
The conversion table this calculator uses
Everything runs through oral morphine milligram equivalents as the hub. These factors are the widely published equianalgesic values; they are printed here so you can check the arithmetic by hand, which you should.
| Drug and route | Oral MME per mg | Typical IR interval |
|---|---|---|
| Morphine, oral | 1 | every 4 hours |
| Morphine, IV | 3 | every 4 hours |
| Oxycodone, oral | 1.5 | every 4 to 6 hours |
| Hydrocodone, oral | 1 | every 6 hours |
| Hydromorphone, oral | 4 | every 4 hours |
| Hydromorphone, IV | 20 | every 4 hours |
| Oxymorphone, oral | 3 | every 6 hours |
| Codeine, oral | 0.15 | every 6 hours |
| Tramadol, oral | 0.1 | every 6 hours |
| Methadone | refused | specialist only |
| Buprenorphine | refused | specialist only |
| Fentanyl patch | not included | own conversion table |
Why methadone and buprenorphine are refused
Methadone's potency relative to morphine is not a constant: it climbs steeply and nonlinearly with the morphine dose you are converting from, its half-life is long and variable, and it prolongs the QT interval. A factor that is safe at 60 MME is dangerous at 300. Buprenorphine is a partial agonist with its own ceiling effects and precipitated-withdrawal behavior. Converting either drug with a fixed ratio is exactly how patients get hurt, so this calculator will not print a number for them. Involve pain medicine or palliative care.
Why the oral to IV ratio differs by drug
First-pass metabolism. Oral morphine loses roughly two thirds of itself to the liver before reaching the circulation, so 30 mg by mouth does what 10 mg does IV. Hydromorphone is hit even harder, which is why its IV form is so much more potent per milligram than its oral form. Oxycodone, by contrast, has high oral bioavailability, which is part of why it needs no IV counterpart on most formularies. When you switch a patient between routes and forget this, the error runs three to five fold in whichever direction you got wrong.
Renal and hepatic adjustment
Morphine's metabolites are renally cleared and neurotoxic when they accumulate: in kidney failure they cause myoclonus, sedation and delirium, so morphine is the wrong opioid in advanced CKD. Hydromorphone and fentanyl are the usual choices there, at reduced doses and extended intervals. In cirrhosis, first-pass metabolism falls and half-lives stretch, so start lower and dose less often. In both populations, the sedation you cause today arrives tomorrow: metabolite accumulation is delayed, which is why the overdose call so often comes on hospital day three. The overnight response to that call is covered in common night calls.
When to rotate rather than escalate
If a patient is on escalating doses with worsening pain control, or is comfortable but toxic (sedated, confused, myoclonic), rotation often beats escalation. Incomplete cross-tolerance means the new drug is more effective per equivalent milligram than the math predicts, which is precisely why the reduction this calculator applies exists, and why skipping it is the classic rotation error. Opioid-induced sedation and delirium overlap heavily with the confusion workup in the ICU delirium guide; check the medication list before you order the head CT.
How to write a taper
Decide the timeline out loud with the patient, then write it as explicit dated steps, not "wean as tolerated," which no one ever executes. A common shape: reduce the total daily dose by 10 to 25 percent per step, with steps every one to four weeks depending on how long the patient has been on opioids; slower at the end than the beginning. Convert the plan into specific orders: the dose at each step, the stop date, and what to do about withdrawal symptoms. Document the plan and the conversation, because a taper that lives only in your head is a refill request waiting to happen.