GLP-1 Weight Loss Calculator
Estimate your possible weight-loss progress over time based on clinical trial data. View projected ranges and milestones for semaglutide, tirzepatide, and retatrutide.
Projections based on published clinical trial ranges. Individual results vary significantly.
Enter your starting weight and click "Calculate Projection" to see your results.
What These Estimates Mean
The projections shown in this calculator are based on average outcomes from published clinical trials. They are not guarantees and should not be interpreted as personalized medical predictions. Individual results can differ substantially due to numerous factors.
The three scenarios — conservative, average, and optimistic — reflect the range of outcomes observed in clinical trials. The "conservative" result typically represents the lower quartile of outcomes, while "optimistic" represents the upper quartile.
Factors that affect your actual results include: medication adherence, speed of dose escalation, diet quality (particularly protein intake), physical activity level, starting weight, metabolic health, sleep quality, and individual biological variation.
For the most accurate personal results, we recommend comparing your actual weight loss to these projections after the first 4–8 weeks, then adjusting your expectations accordingly. The projections become less reliable at very long timelines (beyond 48–52 weeks) because most clinical trials don't extend beyond this duration.
Clinical-Trial Ranges vs Real-World Outcomes
Clinical trials are conducted under controlled conditions — participants receive regular counseling, nutritional support, and close follow-up. This typically produces higher average weight-loss outcomes than real-world practice.
In real-world settings, results vary more widely. Factors like inconsistent medication use, less stringent dietary changes, and lack of professional support can reduce outcomes. Conversely, people who exercise consistently and maintain a high-protein diet sometimes exceed trial averages.
The trial ranges used in this calculator correspond to intention-to-treat outcomes (all randomized participants, including those who dropped out), which are more conservative than treatment-completer results.
| Source | Semaglutide | Tirzepatide | Retatrutide |
|---|---|---|---|
| Clinical trial (average) | ~15% | ~21% | ~24% (Phase 2) |
| Real-world range | 8–17% | 12–25% | Limited data |
Projection Model: Exponential decay model that accounts for the dose-escalation ramp-up phase of GLP-1 therapy.
Semaglutide: STEP 1-4 trials (Wilding et al., NEJM 2021). 2.4 mg dose, 68 weeks.
Tirzepatide: SURMOUNT-1 (Jastreboff et al., NEJM 2022). 5/10/15 mg doses, 72 weeks.
Retatrutide: Phase 2 trial (Jastreboff et al., NEJM 2023). Up to 12 mg dose, 48 weeks.
Limitations: This model significantly simplifies weight-loss dynamics. Actual weight loss is non-linear, influenced by dose titration, and varies considerably between individuals.
Frequently Asked Questions
Common questions about GLP-1 weight loss projections.
This calculator provides estimates based on average clinical trial results. Individual results vary significantly based on factors including adherence to medication, diet quality, exercise habits, metabolic health, and dose titration. The projected range (conservative to optimistic) accounts for some of this variability.
In the STEP clinical trials, participants using semaglutide 2.4 mg lost an average of approximately 15% of body weight over 68 weeks. Results ranged from about 10% to 17% depending on the trial and population.
Yes. In the SURMOUNT trials, tirzepatide showed greater average weight loss than semaglutide — approximately 21% at the highest dose over 72 weeks, compared to approximately 15% for semaglutide. Tirzepatide is a dual GIP/GLP-1 agonist, while semaglutide targets only GLP-1.
Because weight loss outcomes vary widely between individuals. Showing a range (conservative, average, optimistic) is more honest and useful than a single number. The range is based on the spread of outcomes observed in clinical trials.
Key factors include: medication adherence, dose titration speed, diet quality (especially protein intake), physical activity level, starting weight, metabolic health, sleep quality, and individual biological response to the medication.
Yes, we include emerging retatrutide data from Phase 2 clinical trials. In these trials, participants on the highest dose achieved up to approximately 24% mean body weight loss at 48 weeks. Phase 3 trials are ongoing, and final data may differ.
Related Tools
Explore our other free GLP-1 calculators and planning tools.
Calculate daily protein and hydration targets for GLP-1 medication users.
Plan your injection schedule with reminders and dose escalation tracking.