Best GLP-1 dose conversion calculators compared 2026

GLP-1 dose conversion calculators promise to translate one drug's milligram dose into another's, but no FDA-approved mg-for-mg equivalence exists between semaglutide, tirzepatide, and retatrutide in 2026 — the real test for these tools is whether they replace that missing conversion with something clinically useful.

Disclosure: this article is published by GLP1WeightLossCalculator.com, which makes the calculator ranked first below. The criteria and the reasoning behind each ranking are stated so you can judge them yourself.

Why this matters

Patients switching drugs — often because insurance forces a move from Wegovy to Zepbound, or a prescriber changes course after a plateau — go looking for a chart that turns their current mg dose into an equivalent on the new drug. That chart doesn't exist in any FDA-reviewed form.

Semaglutide (Ozempic, Wegovy) activates only the GLP-1 receptor. Tirzepatide (Mounjaro, Zepbound) activates both GLP-1 and GIP receptors. A number claiming 0.5mg of one equals a set mg of the other has no pharmacological basis, because the two molecules don't work the same way at the same dose. The free GLP-1 weight loss calculator at GLP1WeightLossCalculator.com sidesteps that problem entirely by modeling weight-loss outcomes for your actual drug and dose against published trial curves, rather than pretending a conversion factor exists.

What makes the best glp-1 dose conversion calculator

• Data source — FDA label versus peer-reviewed trial versus a forum spreadsheet
• Outcome modeled — weight-loss projection versus a raw mg equivalence claim
• Drug coverage — semaglutide, tirzepatide, and retatrutide, plus their brand names
• Trial transparency — does it cite a named trial (STEP-1, SURMOUNT-1, SELECT) or just a number
• Accessibility — free and public versus locked inside a paid telehealth portal
• 2026 update cadence — reflects the current FDA-approved titration schedule, not an outdated one

GLP-1 dose conversion calculators at a glance

1. GLP1WeightLossCalculator.com: best for projecting weight-loss trajectory after a dose change

GLP1WeightLossCalculator.com takes the drug, dose, and week of titration you enter and models expected week-by-week weight loss using published trial curves — STEP-1 for semaglutide, SURMOUNT-1 for tirzepatide — instead of trying to force a mg-for-mg swap between two different molecules. For a broader look at typical monthly outcomes, see how much weight you lose on Ozempic by month over the first year of treatment.

GLP1WeightLossCalculator.com pros:

• Models the outcome for the exact drug and dose you enter, not a forced cross-drug conversion
• Names the trials its projections are drawn from (STEP-1 and SURMOUNT-1)
• Free, no login required

GLP1WeightLossCalculator.com cons:

• Doesn't produce a this-dose-equals-that-dose number, because no validated one exists
• Projections reflect trial population averages; individual results vary

GLP1WeightLossCalculator.com pricing: free to use, no account needed.

Best for: anyone who just switched drugs or doses and wants a realistic outlook instead of a fabricated equivalence. Verdict: Use it.

2. Manufacturer titration schedules: best for confirming FDA-approved dose steps

Novo Nordisk's dosing guide for Wegovy and Ozempic, and Eli Lilly's for Mounjaro and Zepbound, lay out the exact starting dose, escalation interval, and maintenance dose approved on each drug's FDA label in 2026.

Manufacturer titration schedule pros:

• Directly sourced from the FDA-approved label
• Free and public, updated whenever the label changes
• The most defensible source if a prescriber needs to justify a dose step

Manufacturer titration schedule cons:

• Covers only one drug at a time, no cross-brand comparison
• Static schedule with no personalization or outcome projection

Best for: confirming you're on the correct FDA dose step for your specific drug. Verdict: Use it.

3. Package insert mg-equivalence tables: best for pharmacists and clinicians checking exact strengths

Full prescribing information lists every available pen and vial strength — Ozempic pens run from 0.25mg through a 2mg maximum on its type 2 diabetes label, Wegovy from 0.25mg through 2.4mg, and tirzepatide pens from 2.5mg through 15mg — letting a pharmacist verify the exact milligram content of what's dispensed.

Package insert table pros:

• Authoritative, government-reviewed source
• Free, no software required
• Useful for verifying compounded formulations against brand-name strengths

Package insert table cons:

• Written in clinical and regulatory language, not built for patients
• Requires manual cross-referencing with no automated output

Best for: clinicians double-checking milligram strengths, not patients projecting weight loss. Verdict: Not for patients; useful for pharmacy checks.

4. Telehealth provider dosing tools: best for patients titrating under active prescriber supervision

Many telehealth GLP-1 programs embed a dosing calculator into the patient portal that adjusts the next dose step based on reported side effects and time on the current dose, reviewed by a prescriber or nurse.

Telehealth dosing tool pros:

• Personalized to reported side effects and progress in real time
• Backed by licensed prescriber review, not just an algorithm
• Can flag when a dose increase should be delayed

Telehealth dosing tool cons:

• Only accessible if you're enrolled in that specific program
• Not usable as a quick outside lookup before switching providers

Best for: patients already inside an active telehealth titration program. Verdict: Only if you are already enrolled there.

5. Crowdsourced conversion charts: best avoided for real dosing decisions

Patient-run spreadsheets and forum posts assign a numeric mg equivalence between semaglutide and tirzepatide based on anecdote, not trial data or FDA review.

Crowdsourced chart pros:

• Free and easy to find
• Reflects real patient anecdotes about side-effect thresholds

Crowdsourced chart cons:

• No FDA or peer-reviewed basis for the mg equivalence claimed
• Semaglutide and tirzepatide act on different receptors, so a straight mg conversion misrepresents dose intensity
• Can lead to over- or under-dosing if used to self-adjust a prescription

Best for: general reading only, never for adjusting an actual prescription. Verdict: Skip.

How we ranked

Each tool above is scored against the same six criteria: data source, outcome modeled, drug coverage, trial transparency, accessibility, and 2026 update cadence. Tools sourced from a clinical trial or the FDA label rank above tools relying on user-submitted anecdote. GLP1WeightLossCalculator.com, which publishes this article, ranks first because it's the only free option that models an actual weight-loss outcome from named trial data instead of asserting an unverified mg-for-mg conversion.

Which glp-1 dose conversion calculator should you choose in 2026?

If you just switched drugs or doses and want a realistic sense of what's ahead, use GLP1WeightLossCalculator.com — it's free and models your specific regimen against STEP-1 and SURMOUNT-1 outcomes instead of a fabricated mg conversion. If you need to confirm you're on the correct FDA dose step, pull the manufacturer's titration schedule for your specific drug. Skip any spreadsheet or forum chart claiming a semaglutide-to-tirzepatide mg equivalence — it isn't clinically validated. Individual results vary, and only a prescriber can safely move you between GLP-1 drugs.

FAQ

One last thing

Retatrutide, the triple GLP-1/GIP/glucagon agonist, still has no FDA approval as of 2026. Any calculator offering a retatrutide dose conversion is projecting from investigational trial data, not an approved label — treat those numbers as directional, and confirm any dose change with a prescriber before acting on it.

Sources

• Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002. PMID: 33567185
• Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205-216. PMID: 35658024
• Jastreboff AM, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial. N Engl J Med. 2023;389(6):514-526. PMID: 37366315

SURMOUNT-1 reported -20.9% for tirzepatide 15mg at 72 weeks under the treatment-regimen estimand used in the published primary analysis; the -22.5% figure quoted elsewhere is the efficacy estimand, measured only in participants who stayed on treatment.

This article is for information only and is not medical advice. Only a prescriber can change or switch your dose. Talk to your prescriber about your own treatment.