Opioid Conversion Calculator: Equianalgesic Dose Conversion

Convert Doses — Opioid Conversion Calculator

How to Use Opioid Conversion Calculator: Equianalgesic Dose Conversion

1. Step 1: Choose source medication

   Select the current opioid and enter either the total daily dose (mg/day) or the per‑dose amount with doses/day. For fentanyl patches, use the mcg/hr strength.

2. Step 2: Check source MME/day

   The tool converts the source regimen to morphine milligram equivalents (MME/day). This is an exposure estimate, not a prescribing rule.

3. Step 3: Apply cross‑tolerance reduction

   Pick a reduction (commonly 25–50%) to account for incomplete cross‑tolerance when switching opioids.

4. Step 4: Select target medication

   Choose the target opioid. Optionally add target doses/day to see an estimated per‑dose amount.

5. Step 5: Review rounding guidance

   Review mg/day or mcg/hr results and optional rounding suggestions to common strengths. Confirm details in a trusted reference.

Key Features

• Drug-to-drug conversion capabilities
• Comprehensive equianalgesic tables
• Stepwise dose conversion workflow
• Integrated safety checkpoints

Understanding Results

Formula

The conversion follows a three‑step workflow. 1) Convert the source regimen to morphine milligram equivalents (MME/day) using an equianalgesic factor. For example, oxycodone has a factor of 1.5, so 20 mg/day is 30 MME/day. Certain drugs have special rules: fentanyl patches use mcg/hr × 2.4 ≈ MME/day, while methadone is non‑linear and depends on the total daily methadone dose. 2) Apply a cross‑tolerance reduction (commonly 25–50%) to reduce the new opioid’s starting dose. 3) Convert the adjusted MME/day to the target drug by dividing by the target factor. If you enter target doses/day, the calculator also displays an approximate per‑dose amount for quick review.

Reference Ranges & Interpretation

Many organizations flag daily MME ranges to help contextualize exposure. While not a prescribing rule, totals around 50 MME/day often prompt additional caution, and totals around 90 MME/day are commonly considered high exposure. These markers are shown only to support education and safety reviews. Final clinical decisions require a full patient assessment including indication, prior response, co‑medications, and monitoring plans.

Assumptions & Limitations

Equianalgesic tables are averages from limited data and can vary by source. Formulation (IR vs ER), patient factors (age, renal/hepatic function), and drug interactions can meaningfully change response. Methadone and transdermal fentanyl have complex kinetics and conversion nuance; the calculator uses common educational factors, not clinical protocols. Buprenorphine is intentionally excluded from MME‑based conversions. Always confirm results in a trusted reference and use professional judgment.

Complete Guide: Opioid Conversion Calculator: Equianalgesic Dose Conversion

Use the opioid conversion calculator to convert between opioids, estimate MME/day, apply cross‑tolerance reduction, and review clear results for education.

What the calculator solves

Switching between opioids requires translating the current regimen into an estimated equianalgesic dose of the new medication. Doing this by hand involves several steps: calculating total daily intake, consulting equianalgesic factors, applying a cross‑tolerance reduction, and then translating the result into practical dosing. The process is error‑prone when rushed. This tool streamlines those steps so you can review an evidence‑based estimate in seconds, keep assumptions visible, and avoid mental arithmetic while you focus on clinical context.

The goal is transparency, not automation. The output highlights conversions and assumptions so you can verify each part against a trusted reference. You can also pair the conversion with theMorphine Equivalent Calculatorwhen you want to review a patient’s total MME exposure more broadly.

How the opioid conversion calculator works

The calculator converts the source regimen to morphine milligram equivalents (MME/day) using published factors. For example, 10 mg of oxycodone has an MME of 15; a fentanyl patch rated 25 mcg/hr counts as about 60 MME/day. After conversion, you select a cross‑tolerance reduction (commonly 25–50%). The tool reduces the MME accordingly, then divides by the target drug’s factor to estimate the target daily dose. If you provide a target frequency, it shows an estimated per‑dose amount for quick planning.

Equianalgesic factors differ by source and context. The factors in this tool reflect common educational tables and are intended for learning, not prescribing. Always cross‑check with a trusted reference and align with local protocols before making clinical decisions.

MME: what it is and isn’t

MME is a way to express total opioid exposure in “morphine‑equivalent” terms so that different drugs can be compared on a common scale. It is not a potency guarantee, a toxicity prediction for an individual, or a dosing rule. People metabolize and respond to opioids differently; comorbidities and co‑medications also matter. Educational thresholds (for example, extra caution around 50 MME/day and high exposure at 90 MME/day) are signals to slow down, reassess, and apply careful judgment, not hard lines.

For a total‑exposure review, you can compute all concurrent opioids with theMME calculator, then use this page to translate that exposure into a specific target agent if a switch is being considered.

Cross‑tolerance: why reduce the target dose

Tolerance to the current opioid does not fully transfer to a different opioid. To lower risk during a switch, many references recommend starting the new opioid at a reduced equianalgesic dose (often 25–50% lower). That reduction is a pivotal safety step and is built into this calculator. The exact reduction depends on the patient’s status, the clinical setting, and the specific agents involved. Choosing a higher reduction provides a more conservative starting point, with room for careful titration.

Special cases: methadone and fentanyl

Methadone has non‑linear equianalgesic relationships: its conversion factor increases as the daily methadone dose rises. For education, this calculator applies bracketed factors (for example, 1–20 mg/day ≈ ×4, 21–40 mg/day ≈ ×8, 41–60 mg/day ≈ ×10, ≥61 mg/day ≈ ×12). When converting to methadone from an MME value, the inversion uses the bracket that best matches the estimated result. This is only a rough guide; clinical conversions may require experienced oversight and slower titration.

Transdermal fentanyl is expressed in mcg/hr. A commonly cited educational approximation is 1 mcg/hr ≈ 2.4 MME/day. The tool uses that factor for both directions (patch ↔ MME). Factors vary across sources and situations; always verify with a reference.

Input details: per‑dose vs per‑day

You can enter either a total daily dose or a per‑dose amount with the number of doses per day. For transdermal fentanyl, enter the patch strength (mcg/hr). For the target agent, specifying doses per day lets the calculator estimate an approximate per‑dose amount. This is useful when comparing immediate‑release schedules (for example, four doses per day) or when planning the first few administrations during a switch.

If you need to design a full schedule or translate mg into mL or tablets, theDosage Calculatorcan help with per‑dose vs per‑day math, maximums, and practical units. For pediatrics, use thePediatric Dose Calculator.

Rounding and practical strengths

Results include optional rounding suggestions to common strengths (for example, 5, 7.5, 10, 15 mg tablets; 12, 25, 50 mcg/hr patches). Rounding is not a recommendation. It is there to save time when you are matching a plan to available products or checking plausibility. Always confirm that rounded values are reasonable, that the formulation matches your intent (IR vs ER), and that product labeling supports splitting or administration method.

Safety checks and patient factors

A safe switch considers more than equianalgesic math. Evaluate renal and hepatic function, drug interactions (for example, CYP inhibitors/inducers), age, frailty, sleep‑disordered breathing, and concomitant sedatives. If reduction or titration is needed, consider a slower approach with closer follow‑up. For renal dosing questions, theeGFR Calculatorhelps quantify kidney function. For timing and accumulation considerations, see theDrug Half‑Life Calculator.

Pain is subjective and dynamic. If you are tracking symptoms, thePain Scale Calculatorcan help standardize documentation alongside functional goals.

Worked examples

Example A — oxycodone to morphine: A patient takes oxycodone 10 mg three times daily. Daily mg = 30 mg. MME = 30 × 1.5 = 45. Apply a 25% reduction → 33.75 MME. Morphine factor is 1, so target ≈ 33.75 mg/day. If planning four daily doses, per dose ≈ 8.4 mg. A practical rounded start might be 7.5–10 mg per dose depending on clinical judgment and monitoring.

Example B — morphine to fentanyl patch: A patient takes morphine 60 mg/day. MME = 60. Apply a 25% reduction → 45 MME. Fentanyl patches use ≈ 2.4 MME/day per mcg/hr, so 45 ÷ 2.4 ≈ 18.75 mcg/hr. The nearest common strength is 12 or 25 mcg/hr; in many contexts, starting at 12 mcg/hr with reassessment is more conservative, but clinical guidance and individual factors govern.

Example C — converting to methadone: Suppose the adjusted MME is 120. Using bracketed inversion, 120 ÷ 10 ≈ 12 mg/day would fall within the 41–60 mg/day methadone bracket (factor ≈10). Because methadone builds and has variable kinetics, a cautious plan with close follow‑up is essential; the number shown is an educational estimate rather than a directive.

Related tools

• Morphine Equivalent Calculator — review total MME exposure.
• Dosage Calculator — translate mg into mL/tablets with caps.
• Pediatric Dose Calculator — child‑specific dose math.
• Drug Half‑Life Calculator — consider accumulation and timing.
• eGFR Calculator — support renal adjustments.
• Pain Scale Calculator — track symptoms and function.

Browse the full calculators index or see more tools in theClinical & Medications category.

References and further reading

For educational context on MME and safe opioid practices, see:

• Centers for Disease Control and Prevention (CDC) — guidance on morphine milligram equivalents and caution thresholds.cdc.gov
• U.S. National Library of Medicine (NIH/MedlinePlus) — general opioid information and safety topics.NIDA — Opioids

Disclaimer: This article and the calculator are for education only and do not constitute medical advice. Conversions are estimates based on common equianalgesic factors; clinical care requires individualized assessment, monitoring, and consultation with authoritative references.

Frequently Asked Questions