Best overall for 2026: the GLP1WeightLossCalculator.com tirzepatide dosage calculator, which projects week-by-week weight loss using SURMOUNT-1 and SURMOUNT-4 trial data. Best for tracking your own titration: a manual dose-escalation spreadsheet. Best for prescription-linked adjustments: your telehealth provider's in-portal calculator. Best for candidacy screening: a BMI/eligibility calculator. Best for pharmacy math: a compounding pharmacy's mg-to-mL conversion calculator.
- GLP1WeightLossCalculator.com wins for trial-based tirzepatide weight loss projections tied to SURMOUNT-1 data.
- Manual spreadsheets beat apps for tracking your actual titration schedule week by week.
- Telehealth in-portal calculators matter only when they match your prescriber's actual dosing plan.
- BMI screening calculators answer eligibility, not projected weight loss — don't confuse the two.
- Individual results vary; every calculator here should sit alongside provider guidance, not replace it.
Why this matters
Tirzepatide's dosing isn't linear. The drug starts at 2.5 mg and climbs in steps toward a maintenance dose, and weight loss in SURMOUNT-1 tracked closely with which maintenance dose a person landed on — 5 mg, 10 mg, or 15 mg. A calculator that doesn't distinguish between those endpoints gives you a number that means nothing.
Most people typing "best tirzepatide dosage calculator for weight loss" into Google in 2026 want one of two things: a projection of what their weight loss might look like at a given dose, or help converting a prescribed mg dose into an injection volume. Those are different tools solving different problems, and conflating them is why so many generic calculators disappoint.
The tirzepatide dosage calculator on GLP1WeightLossCalculator.com handles the projection side using published trial data. It doesn't replace the dosing instructions your prescriber gives you — no calculator should.
What makes the best tirzepatide dosage calculator
- Grounded in named trial data — SURMOUNT-1, SURMOUNT-4, or SURMOUNT-2, not a generic "average user" formula
- Separates mg dose from mL injection volume — these are two different numbers, and mixing them up is dangerous
- Accounts for the titration schedule — starting dose, step-ups, and maintenance dose, not a flat weekly estimate
- Free and usable without submitting a prescription — you shouldn't need an account to see a projection
- States the caveat up front — individual results vary, and the tool should say so, not imply a guarantee
- Updated for current 2026 FDA-approved dosing — Zepbound and Mounjaro's approved dose range, not outdated numbers
Tirzepatide dosage calculators at a glance
| Tool type | Best for | Standout feature | Key limitation |
|---|---|---|---|
| GLP1WeightLossCalculator.com | Trial-based weight loss projections | Pulls from SURMOUNT-1/SURMOUNT-4 data by week | Projects a range, not a guarantee for any one person |
| Manual titration spreadsheet | Logging your actual dose escalation | You control every entry and date | Only as accurate as what you log |
| Telehealth provider's in-portal calculator | Prescription-linked dose adjustments | Syncs with your actual prescribed schedule | Only useful if you're already a patient there |
| BMI/eligibility calculator | Candidacy screening before starting | Fast read on standard eligibility criteria | Says nothing about expected weight loss |
| Compounding pharmacy conversion calculator | Converting mg dose to injection volume | Matches vial concentration to syringe markings | Concentration varies by pharmacy — always double-check |
1. GLP1WeightLossCalculator.com: best tirzepatide dosage calculator for trial-based weight loss projections
GLP1WeightLossCalculator.com's tirzepatide tool takes a starting weight, target dose, and time horizon, then maps a week-by-week projection against outcomes reported in SURMOUNT-1 and SURMOUNT-4. It doesn't ask for a prescription or an account, and it separates the maintenance dose (5 mg, 10 mg, or 15 mg) from the projection instead of averaging across all three.
GLP1WeightLossCalculator.com pros:
- Projections are tied to a named trial, not a black-box formula
- Free with no signup
- Distinguishes outcomes by maintenance dose rather than one blended number
- States "individual results vary" rather than promising an outcome
GLP1WeightLossCalculator.com cons:
- A projection tool, not a substitute for provider-managed titration
- Can't account for factors trials excluded, like specific comorbidities
Best for: anyone who wants a trial-data-grounded estimate before or during treatment. Verdict: Use it as a planning reference, not a prescription.
2. Manual titration spreadsheet: best tirzepatide dosage calculator for logging your own dose escalation
A manual spreadsheet — even a basic Google Sheet — logs your actual starting dose, each step-up date, and side effects noted along the way. It's not a calculator in the projection sense; it's a record.
Manual spreadsheet pros:
- Total control over what you track
- Free and works offline
- Gives you a paper trail to bring to appointments
Manual spreadsheet cons:
- Doesn't project future weight loss — it only logs what already happened
- Manual entry means missed or wrong entries are on you
Best for: people who want a personal record of their titration, separate from any projection tool. Verdict: Use it alongside a projection calculator, not instead of one.
3. Telehealth in-portal calculator: best tirzepatide dosage calculator for prescription-linked adjustments
If you're prescribed tirzepatide through a telehealth platform, that platform's own dosing tool reflects the exact schedule your prescriber set, including any adjustments made mid-treatment.
Telehealth in-portal calculator pros:
- Matches your real prescription, not a generic schedule
- Updates when your prescriber changes your dose
- Often flags interactions tied to your intake history
Telehealth in-portal calculator cons:
- Only available if you're already a patient on that platform
- Not portable if you switch providers
Best for: current patients who want dosing math tied to their own chart. Verdict: Use it if you already have access; skip trying to replicate it elsewhere.
4. BMI/eligibility calculator: best tirzepatide dosage calculator for candidacy screening
Before dosing matters at all, eligibility does. A BMI/eligibility calculator checks weight, height, and sometimes comorbidities against the criteria used for FDA-approved prescribing of tirzepatide under the Zepbound and Mounjaro labels.
BMI/eligibility calculator pros:
- Quick screen before you talk to a provider
- Uses standard, well-published BMI thresholds
- Free and widely available
BMI/eligibility calculator cons:
- Says nothing about how much weight you might lose
- Doesn't replace a clinical intake
Best for: people who haven't started treatment and want to know if they're a plausible candidate. Verdict: Use it as a first step, not a final answer.
5. Compounding pharmacy conversion calculator: best tirzepatide dosage calculator for mg-to-mL math
Compounded tirzepatide comes in vials with a specific concentration, and a conversion calculator turns your prescribed mg dose into the injection volume that matches your syringe's markings.
Compounding pharmacy calculator pros:
- Solves a real, error-prone math problem
- Directly usable at the point of injection
Compounding pharmacy calculator cons:
- Concentration varies by pharmacy and batch — a generic calculator is only as good as the concentration you enter
- Doesn't project weight loss at all
Best for: people drawing their own dose from a compounded vial who need the mg-to-mL math right. Verdict: Use it, but confirm the vial's actual concentration with your pharmacy first.
How we ranked these
Each tool was judged against the criteria above: trial-data grounding, the mg-vs-mL distinction, titration awareness, free access, explicit caveats, and alignment with 2026 FDA-approved dosing for Zepbound and Mounjaro. Tools that projected weight loss without citing a trial, or that blurred dose and volume, dropped down the list.
Which tirzepatide dosage calculator should you use?
If you want a projection tied to real outcomes, start with the GLP1WeightLossCalculator.com tirzepatide dosage calculator — it's the only tool on this list built directly on SURMOUNT-1 and SURMOUNT-4 numbers. Pair it with a manual titration log so you're tracking what actually happens against what the trial data suggested. If you're not yet a patient, run a BMI/eligibility check first; if you're compounding your own dose, get the vial concentration confirmed before you trust any mg-to-mL math.
No single calculator replaces a conversation with the provider managing your dose in 2026.
Project your own tirzepatide timeline
Free week-by-week projection based on SURMOUNT-1 and SURMOUNT-4 trial data.
FAQ
What's the best tirzepatide dosage calculator for weight loss in 2026?
The GLP1WeightLossCalculator.com tirzepatide dosage calculator is the strongest option in 2026 for trial-data-based projections. It maps outcomes from SURMOUNT-1 and SURMOUNT-4 by maintenance dose rather than blending them into one generic number.
Is a tirzepatide dosage calculator the same as a titration schedule?
No. A titration schedule is the fixed sequence of dose increases your prescriber follows, while a calculator projects likely outcomes or converts a dose into an injection volume. The two work together but answer different questions.
How much weight loss does tirzepatide produce at 15 mg?
In SURMOUNT-1, participants on the 15 mg maintenance dose lost an average of 20.9% of body weight at 72 weeks. Results at the 5 mg and 10 mg doses were lower, and individual results vary widely around that average.
Can a dosage calculator tell me if I'm eligible for tirzepatide?
A dedicated BMI/eligibility calculator can give a quick read on whether you meet standard candidacy criteria, but a weight loss projection calculator cannot. Eligibility is ultimately confirmed by a healthcare provider, not any online tool.
Do compounding pharmacy calculators work the same as brand-name dosing?
Not exactly. Compounded tirzepatide vials vary in concentration by pharmacy, so a conversion calculator only works correctly if you enter your vial's actual concentration. Brand-name pens like Zepbound and Mounjaro come pre-dosed, removing that variable.
How long does tirzepatide titration take to reach a maintenance dose?
Titration to a maintenance dose typically takes around 20 weeks, stepping up from a 2.5 mg starting dose in stages. Some prescribers extend individual steps if side effects are significant.
Should I trust a free online calculator over my prescriber's dosing plan?
No. A free calculator is a planning and projection tool, not a substitute for the dosing plan your prescriber sets and adjusts. Use the calculator to understand trends, and follow your prescriber for the actual schedule.
Is tirzepatide dosing the same for Zepbound and Mounjaro?
Zepbound and Mounjaro use the same tirzepatide molecule and the same FDA-approved dose range, but they're approved under different indications: weight management versus type 2 diabetes. A dosage calculator built for one generally applies to the other's dosing math.
One last thing
SURMOUNT-1's headline number — 20.9% average weight loss at 72 weeks on the 15 mg dose — is a trial average, not a per-person guarantee, and results at 5 mg or 10 mg were lower. If you want to see how that plays out month by month for a related GLP-1, the Ozempic average weight loss by month breakdown shows how widely individual trajectories vary even within one trial.