Weight Loss Provider Guide · Calculator
GLP-1 Weight Loss Calculator
Estimate how much weight you could lose on Wegovy, Zepbound, Ozempic, Mounjaro, or compounded semaglutide at 3, 6, 12, or 18 months — projections anchored to STEP and SURMOUNT clinical trial data, not guesswork.
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By WPG Research Team · Last updated: · Last verified: · Next review: August 2026
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FDA-approved for chronic weight management
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6
medications
18
month chart
FDA
trial data
Trajectory
Weight over 18 months on Wegovy
Month 1
6 lbs
appetite shifts
Month 3
16 lbs
first clothing size
Month 6
24 lbs
BMI category shift
Month 12
30 lbs
approaching maintenance
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What this GLP-1 weight loss calculator actually tells you
This calculator answers the question most people are typing when they look for a GLP-1 weight loss calculator: if I start this medication at my weight, how much could I realistically lose? It does that by anchoring the projection to the mean percentage body weight loss observed in the pivotal Phase 3 trials for each medication — not to a guessed calorie deficit, not to before-and-after marketing photos, and not to a single user's anecdotal result.
The projection model treats weight loss as a logarithmic approach to the trial endpoint. In plain language: most of the loss happens in the first six months, the curve flattens through months 9 to 12, and almost everyone reaches a maintenance plateau between months 14 and 18. That matches the trajectory observed in the STEP and SURMOUNT extension data, which is why a 12-month projection and an 18-month projection on the same dose are usually only a few pounds apart.
The eligibility verdict in the result panel reflects the most common prescribing thresholds used by U.S. clinicians: a BMI of 30 or higher, or a BMI of 27 or higher with a weight-related condition such as high blood pressure, high cholesterol, sleep apnea, or type 2 diabetes. That is a screening framework, not a diagnosis. A licensed clinician must confirm whether a GLP-1 medication is appropriate for you based on your full health history.
Everything runs in your browser. No weight, height, BMI, or health input is sent to a server, written to a database, or stored in a cookie. The next-step quiz only sees a small set of bucketed (non-exact) inputs in your browser session — and only if you choose to use it.
How this calculator is built
1. Trial-anchored loss percentages
Each drug-and-dose combination is anchored to a specific Phase 3 trial result for mean percentage weight loss in the trial population at the trial endpoint. Wegovy 2.4 mg uses STEP 1 (68 weeks, ~14.9% mean loss). Wegovy 7.2 mg uses STEP UP (~19%). Zepbound uses SURMOUNT-1 at 72 weeks (15.0% / 19.5% / 20.9% mean loss at 5, 10, and 15 mg). Ozempic uses SUSTAIN trial averages at 1 mg and 2 mg. Mounjaro uses SURPASS / SURMOUNT-2 averages at 10 mg and 15 mg, where mean loss is lower because the trial population had type 2 diabetes. Compounded semaglutide and compounded tirzepatide are extrapolated from the corresponding branded molecule's trial data with a wider responder range to reflect real-world dosing variability across compounding pharmacies.
2. Time-distributed projection curve
The projection at any month is computed as progress(weeks) = 1 − exp(−3 × weeks ÷ plateauWeeks), calibrated so that approximately 95% of the expected loss is reached at the trial's reported plateau time. Each dose carries its own plateauWeeks value drawn from the corresponding extension trial. This produces the rapid-early, plateau-later trajectory clinicians and trial investigators routinely report.
3. Trial responder range, not a single point
For each dose we also publish a low-end and high-end loss percentage. The low end is roughly the result at the bottom of the trial responder distribution; the high end is roughly the top-quartile completer result. The shaded range on the trajectory chart is that band applied to your starting weight at each point in time. Approximately 10–15% of trial participants did not achieve at least 5% weight loss; do not assume the mean line is your line.
4. Placebo benchmark
The placebo arm of SURMOUNT-1 lost on average 2.4% of body weight over 72 weeks. That benchmark — lifestyle counseling alone, no medication — is the cleanest comparison for the additional weight loss attributable to the medication itself. We display it on the result panel as a contrast number, not as a target.
5. Eligibility framing
The eligibility verdict uses common U.S. prescribing criteria: BMI ≥30, or BMI ≥27 with a weight-related condition. We use the language "may fall within common screening criteria" deliberately — not "you qualify" or "you are eligible". Eligibility for any medication is a clinical determination, not a calculator output. This is a Your Money or Your Life category of content and we treat it that way.
6. Editorial accountability
All trial percentages and methodology choices are reviewed by the Weight Loss Provider Guide research team on a quarterly cadence and within 30 days of any new Phase 3 publication or FDA action affecting an in-scope drug. Corrections are tracked publicly on our Corrections Policy page. If you spot an error in a trial figure or a dose tier, please email [email protected].
Last data review: by the Weight Loss Provider Guide research team. Reviewer attributions for individual medical pages are listed on each respective page; this calculator is published under team byline.
Mean weight loss by drug and dose (Phase 3 trials)
Every percentage in this table is a published mean from the named trial, applied at the trial's primary endpoint. The dose column lists the maintenance dose used in that trial arm.
| Medication | Maintenance dose | Mean loss | Trial | Indication |
|---|---|---|---|---|
| Wegovy (semaglutide) | 2.4 mg | 14.9% | STEP 1 (68 wks) | FDA-approved — weight management |
| Wegovy (semaglutide) | 7.2 mg HD | ~19% | STEP UP | FDA-approved — weight management |
| Zepbound (tirzepatide) | 5 mg | 15.0% | SURMOUNT-1 (72 wks) | FDA-approved — weight management |
| Zepbound (tirzepatide) | 10 mg | 19.5% | SURMOUNT-1 (72 wks) | FDA-approved — weight management |
| Zepbound (tirzepatide) | 15 mg | 20.9% | SURMOUNT-1 (72 wks) | FDA-approved — weight management |
| Ozempic (semaglutide) | 1 mg | ~6% | SUSTAIN trials | FDA-approved — type 2 diabetes (off-label for weight loss) |
| Ozempic (semaglutide) | 2 mg | ~7% | SUSTAIN FORTE | FDA-approved — type 2 diabetes (off-label for weight loss) |
| Mounjaro (tirzepatide) | 10 mg | ~9% | SURPASS / SURMOUNT-2 | FDA-approved — type 2 diabetes (off-label for weight loss) |
| Mounjaro (tirzepatide) | 15 mg | ~12% | SURMOUNT-2 | FDA-approved — type 2 diabetes (off-label for weight loss) |
| Compounded semaglutide | Typical protocol | ~13% (extrapolated) | Extrapolated from STEP 1 | Not FDA-approved as compounded |
| Compounded tirzepatide | Typical protocol | ~18% (extrapolated) | Extrapolated from SURMOUNT-1 | Not FDA-approved as compounded |
Compare Wegovy, Zepbound, Ozempic, and Mounjaro side by side
Frequently asked questions
The questions readers most often ask after running a GLP-1 weight loss projection.
How accurate is a GLP-1 weight loss calculator?
A GLP-1 weight loss calculator gives a directional estimate based on the average percentage body weight loss observed in pivotal clinical trials (STEP 1, STEP UP, SURMOUNT-1, SURMOUNT-2, SUSTAIN, SURPASS), applied to your starting weight and a logarithmic time-distribution curve. Real-world results vary widely depending on adherence, dose escalation, side effects, lifestyle, and how long you stay on the medication. Roughly 10–15% of trial participants did not achieve at least 5% weight loss. Treat this projection as a planning estimate, not a guarantee.
How much weight can I lose on Wegovy in 12 months?
In the STEP 1 trial, adults without type 2 diabetes lost on average 14.9% of starting body weight at 68 weeks on Wegovy 2.4 mg. For a 220 lb starting weight, that is roughly 33 lb at maintenance dose. Results published from the STEP UP trial of Wegovy 7.2 mg show even higher mean loss (~19%). The calculator on this page projects your individual estimate based on your starting weight and the dose you select.
How much weight can I lose on Zepbound (tirzepatide)?
In SURMOUNT-1, adults without type 2 diabetes lost on average 15.0%, 19.5%, and 20.9% of body weight at 72 weeks on Zepbound 5 mg, 10 mg, and 15 mg respectively (mean values; trial-published numbers also include the 22.5% top-dose result for completers). For a 220 lb starting weight at the 15 mg top dose, that is roughly 46 lb of mean expected loss.
Why is weight loss lower on Ozempic and Mounjaro than on Wegovy and Zepbound?
Ozempic (semaglutide) and Mounjaro (tirzepatide) are FDA-approved for type 2 diabetes, not weight management, and their approved dosing tops out lower than the weight-management versions (Wegovy and Zepbound). They use the same active molecules but the trial endpoints, doses, and study populations differed. People with type 2 diabetes also tend to lose less weight on GLP-1 medications than people without diabetes — a finding observed across both the STEP and SURMOUNT programs.
Does weight loss on GLP-1 medications plateau?
Yes. Across the STEP and SURMOUNT trial programs, the rate of loss is fastest in the first three to six months and slows substantially by month 12, with most patients reaching a maintenance plateau by months 14–18. The trajectory chart on this calculator uses a logarithmic curve calibrated to the plateau timing observed in extension trials, which is why projected loss at 18 months is only modestly higher than at 12 months for most doses.
What happens if I stop taking my GLP-1 medication?
In the STEP 4 extension trial, participants who stopped semaglutide regained roughly two-thirds of their lost weight within one year. Tirzepatide showed a similar pattern in the SURMOUNT-4 withdrawal study. GLP-1 medications are typically used as long-term maintenance therapy, not short courses. Stopping or changing a GLP-1 medication should always be done with a clinician.
Do I qualify for a GLP-1 medication for weight loss?
Common prescribing criteria for FDA-approved weight-management GLP-1 medications (Wegovy, Zepbound) are a BMI of 30 or higher, or a BMI of 27 or higher with at least one weight-related condition such as high blood pressure, high cholesterol, sleep apnea, or type 2 diabetes. The eligibility verdict in this calculator reflects those common screening criteria but is not a medical determination — only a licensed clinician can confirm whether a GLP-1 medication is appropriate for you based on your full health history.
Are compounded semaglutide and compounded tirzepatide the same as Wegovy or Zepbound?
No. Compounded semaglutide and compounded tirzepatide are prepared by licensed compounding pharmacies. They are not FDA-approved finished drug products and are not the same as FDA-approved generics. Composition, dosing instructions, sterility, and quality vary by pharmacy. The FDA declared the semaglutide and tirzepatide shortages resolved in 2025, ending the enforcement-discretion period that had allowed broad compounding of these molecules. If you consider a compounded path, verify the prescribing clinician, the pharmacy license, the pricing transparency, and the current legal availability.
How does the calculator handle goal weight?
If you enter a goal weight, the calculator computes the percentage of starting body weight you would need to lose, compares that to the mean expected loss for your selected drug and dose, and estimates how many months on average it would take to reach your goal. If your goal exceeds the mean expected loss for the drug you selected, the calculator suggests a higher-efficacy path (for example, escalating from semaglutide to tirzepatide) for you to discuss with a clinician — it does not change the projection itself.
Does the calculator store any of my information?
No. All calculations run in your browser. Nothing about your weight, height, BMI, diabetes status, or goal weight is sent to a server, written to a database, or stored in a cookie or in browser local storage. If you choose to take the next-step quiz, a small set of bucketed (non-exact) inputs is passed in the browser session only and is cleared when you close the tab. We never store exact health values.
How is this projection different from a TDEE or calorie calculator?
A TDEE (Total Daily Energy Expenditure) or calorie-deficit calculator estimates weight change based on energy balance — calories in versus calories out. This GLP-1 calculator instead anchors to the percentage body weight loss observed in randomized clinical trials of each medication. GLP-1 medications work primarily by reducing appetite and food intake, but the published trial outcomes already incorporate that mechanism, lifestyle counseling, dose escalation, and dropout. Anchoring to trial data is the more honest reference point for someone considering medication.
How often is the calculator updated?
The trial percentages, dose tiers, and methodology on this page are reviewed by the Weight Loss Provider Guide research team on a quarterly cadence and within 30 days of any newly published Phase 3 trial result, FDA approval, or label change for an in-scope drug. The "Last verified" date at the top of this page reflects the most recent review.
Why is the placebo arm shown alongside my projection?
In the SURMOUNT-1 placebo arm, participants who received a placebo injection plus the same lifestyle counseling lost on average 2.4% of body weight over 72 weeks. Showing that benchmark next to the medication projection is the cleanest way to illustrate the additional weight loss attributable to the medication itself, separate from the lifestyle program every trial participant received.
What should I do after using the calculator?
If your projection looks reasonable and you fall within common screening criteria, the next step is matching with a clinician-led GLP-1 telehealth program that fits your goals, budget, and preferences. The "Find My Path" quiz at the end of this calculator does that match in about 60 seconds with no signup required. If your situation needs clinician review first (BMI under 27, type 2 diabetes, or any complex health history), use the projection to prepare questions for that visit — do not start, stop, or change any medication based on calculator output.
Important — please read
Educational estimates only. This calculator provides projections based on clinical trial averages and a logarithmic interpolation model. Individual results vary significantly based on adherence, dose escalation, lifestyle, side effects, medical history, and clinician-directed treatment changes. Approximately 10–15% of trial participants do not achieve 5% weight loss.
Not medical advice. This tool does not replace consultation with a licensed healthcare provider. It does not diagnose eligibility, prescribe medication, or guarantee results. Do not start, stop, or change any medication based on calculator output.
FDA indication notes. Wegovy and Zepbound are FDA-approved for chronic weight management. Ozempic and Mounjaro are FDA-approved for type 2 diabetes; use for weight loss is off-label. Compounded semaglutide and tirzepatide are prepared by licensed compounding pharmacies and are not FDA-approved as compounded products; they are not the same as FDA-approved generics. Composition, dosing, and quality vary by pharmacy. Always verify the prescriber, pharmacy license, and current legal status before starting a compounded medication.
Affiliate disclosure. Weight Loss Provider Guide may receive compensation from telehealth providers featured in our quiz and elsewhere on this site. This does not affect calculator output, which is anchored to independent clinical trial data. Our provider rankings are based on published methodology, not commission rates.
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