Semaglutide vs Tirzepatide Weight Loss Estimator
Enter your current weight and treatment duration to estimate predicted weight loss for semaglutide (Ozempic/Wegovy) and tirzepatide (Mounjaro/Zepbound). Results are based on published randomized controlled trial averages.
Based on STEP 1 (NEJM 2021) trial averages at 68-week endpoint. Individual results vary.
Based on SURMOUNT-1 (NEJM 2022) trial averages at 72-week endpoint. Individual results vary.
Estimates are based on published randomized controlled trial data in adults with obesity or overweight. Results vary significantly based on diet, exercise, individual metabolism, and medication adherence. This is not medical advice. Consult a healthcare provider before starting any weight-loss medication.
How this calculator works
Weight loss predictions are modeled using an exponential saturation curve calibrated to match trial-average outcomes at each published endpoint (68 weeks for semaglutide, 72 weeks for tirzepatide).
The curve is calibrated so approximately 63% of the maximum average loss is reached at one-quarter of the trial duration, and ~98% at the full trial duration — consistent with observed trial trajectories in which most weight loss occurs in the first 36 weeks.
Maximum loss percentages are taken from the primary endpoints of STEP 1 (semaglutide, NEJM 2021) and SURMOUNT-1 (tirzepatide, NEJM 2022), the landmark phase 3 trials for each drug in adults with obesity or overweight without type 2 diabetes.
GLP-1 Weight Loss FAQ
How accurate is this GLP-1 weight loss calculator?
The calculator uses average outcomes from the STEP 1 (semaglutide) and SURMOUNT-1 (tirzepatide) randomized controlled trials published in the New England Journal of Medicine. Individual results vary widely — some participants lost significantly more or less than the trial average. Diet, exercise, baseline metabolic health, and medication adherence all affect outcomes.
What is the difference between semaglutide and tirzepatide?
Semaglutide (Ozempic, Wegovy) is a GLP-1 receptor agonist that mimics the incretin hormone GLP-1 to suppress appetite and slow gastric emptying. Tirzepatide (Mounjaro, Zepbound) is a dual GIP/GLP-1 receptor agonist — it activates both GLP-1 and GIP pathways. Clinical trials show tirzepatide produces modestly greater average weight loss than semaglutide, particularly at higher doses.
How long does it take to see results on a GLP-1 medication?
Most people notice appetite suppression within the first 1–2 weeks. Meaningful weight loss (1–3% of body weight) is typically visible by weeks 4–8 as doses are titrated upward. The majority of total weight loss occurs in the first 36 weeks, with a gradual plateau thereafter as the body reaches a new set point.
Do I need a prescription for semaglutide or tirzepatide?
Yes. Both semaglutide (Wegovy for weight loss, Ozempic for type 2 diabetes) and tirzepatide (Zepbound for weight loss, Mounjaro for type 2 diabetes) require a prescription from a licensed healthcare provider. Telehealth platforms can prescribe these medications after an online consultation.
What happens if I stop taking the medication?
Clinical trial extension data shows that most patients regain a significant portion of lost weight after discontinuing GLP-1 medications. Weight regain typically begins within weeks of stopping and can reach pre-treatment levels within 1–2 years without continued use or significant lifestyle changes.