# GLP-1 Weight Loss Calculator — Full Content > A free, clinical-trial-backed calculator that projects personalized week-by-week weight loss for GLP-1 medications including Ozempic, Wegovy, Mounjaro, Zepbound, semaglutide, and tirzepatide. Website: https://www.glp1weightlosscalculator.com --- ## What Are GLP-1 Medications for Weight Loss? GLP-1 receptor agonists (glucagon-like peptide-1 receptor agonists) are a class of prescription medications originally developed for type 2 diabetes that have shown remarkable effectiveness for weight management. These include semaglutide (marketed as Ozempic and Wegovy) and tirzepatide (marketed as Mounjaro and Zepbound). GLP-1 medications work by mimicking a natural gut hormone that regulates appetite. They act on receptors in the brain to reduce hunger and increase feelings of fullness, while also slowing gastric emptying. Tirzepatide is a dual-action drug that targets both the GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors. Retatrutide goes further as a triple agonist, additionally targeting the glucagon receptor, which may contribute to its even greater weight loss efficacy by increasing energy expenditure and fat oxidation. These medications are FDA-approved for chronic weight management in adults with a BMI of 30 or greater (obesity) or a BMI of 27 or greater (overweight) with at least one weight-related health condition such as hypertension, type 2 diabetes, or high cholesterol. --- ## Supported Medications ### Ozempic (Semaglutide) - Type: GLP-1 receptor agonist - Average weight loss: ~12% of body weight - Maximum dose: 2.0 mg per week - Titration schedule: 0.25 mg (weeks 1-4) → 0.5 mg (weeks 5-8) → 1.0 mg (weeks 9-12) → 2.0 mg (week 13+) - Note: Primarily approved for type 2 diabetes; widely used off-label for weight management ### Wegovy (Semaglutide) - Type: GLP-1 receptor agonist - Average weight loss: ~15% of body weight - Maximum dose: 2.4 mg per week - Titration schedule: 0.25 mg (weeks 1-4) → 0.5 mg (weeks 5-8) → 1.0 mg (weeks 9-12) → 1.7 mg (weeks 13-16) → 2.4 mg (week 17+) - FDA-approved specifically for chronic weight management ### Mounjaro (Tirzepatide) - Type: Dual GIP/GLP-1 receptor agonist - Average weight loss: ~22% of body weight - Maximum dose: 15 mg per week - Titration schedule: 2.5 mg (weeks 1-4) → 5.0 mg (weeks 5-8) → 7.5 mg (weeks 9-12) → 10.0 mg (weeks 13-16) → 12.5 mg (weeks 17-20) → 15.0 mg (week 21+) ### Zepbound (Tirzepatide) - Type: Dual GIP/GLP-1 receptor agonist - Average weight loss: ~20% of body weight - Maximum dose: 15 mg per week - Titration schedule: Same as Mounjaro - FDA-approved specifically for chronic weight management ### Generic Semaglutide - Same active ingredient and dosing as Wegovy - Average weight loss: ~15% of body weight ### Generic Tirzepatide - Same active ingredient and dosing as Mounjaro - Average weight loss: ~22% of body weight ### Retatrutide (Investigational) - Type: Triple GIP/GLP-1/Glucagon receptor agonist - Average weight loss: ~24% of body weight (phase 2 trial, 48 weeks) - Maximum dose: 12 mg per week - Titration schedule: 2 mg (weeks 1-4) → 4 mg (weeks 5-8) → 8 mg (weeks 9-12) → 12 mg (week 13+) - Status: Phase 3 trials (TRIUMPH program) currently underway - Developer: Eli Lilly --- ## Clinical Trial Evidence ### STEP-1 Trial — Semaglutide Published in the New England Journal of Medicine in 2021, the STEP-1 trial enrolled 1,961 adults with overweight or obesity. Participants receiving semaglutide 2.4 mg weekly achieved an average weight loss of 14.9% of body weight over 68 weeks, compared to just 2.4% with placebo. - Reference: Wilding JPH, Batterham RL, Calanna S, et al. N Engl J Med. 2021;384(11):989-1002. PMID: 33567185 - URL: https://pubmed.ncbi.nlm.nih.gov/33567185/ ### STEP-1 Extension — Weight Regain After Stopping A follow-up extension study found that participants regained approximately two-thirds of lost weight within one year of stopping treatment, highlighting the importance of sustained therapy. - Reference: Wilding JPH, Batterham RL, Davies M, et al. Diabetes Obes Metab. 2022;24(8):1553-1564. PMID: 35441470 - URL: https://pubmed.ncbi.nlm.nih.gov/35441470/ ### SURMOUNT-1 Trial — Tirzepatide Published in the New England Journal of Medicine in 2022, the SURMOUNT-1 trial demonstrated that tirzepatide at the 15 mg dose produced an average weight loss of 22.5% of body weight over 72 weeks — approaching results typically seen with bariatric surgery. - Reference: Jastreboff AM, Aronne LJ, Ahmad NN, et al. N Engl J Med. 2022;387(3):205-216. PMID: 35658024 - URL: https://pubmed.ncbi.nlm.nih.gov/35658024/ ### SELECT Trial — Cardiovascular Benefits The SELECT cardiovascular outcomes trial showed that semaglutide 2.4 mg significantly reduced major adverse cardiovascular events (heart attack, stroke, and cardiovascular death) in patients with established cardiovascular disease and overweight or obesity, even without type 2 diabetes. A 2026 analysis projected a 1.9-year gain in life expectancy with semaglutide treatment. - Reference: van Sloten TT, et al. Endocr Connect. 2026. PMID: 41800807 - URL: https://pubmed.ncbi.nlm.nih.gov/41800807/ ### Retatrutide Phase 2 Trial — Triple Agonist Published in the New England Journal of Medicine in 2023, this phase 2 trial enrolled 338 adults with obesity. Participants receiving retatrutide 12 mg weekly achieved an average weight loss of 24.2% of body weight at 48 weeks — the largest weight reduction recorded for any anti-obesity medication. At this dose, 100% of participants lost at least 5%, and 83% lost at least 15%. - Reference: Jastreboff AM, Kaplan LM, Frías JP, et al. N Engl J Med. 2023;389(6):514-526. PMID: 37366315 - URL: https://pubmed.ncbi.nlm.nih.gov/37366315/ ### 2026 Meta-Analysis — GLP-1 Agonists for Weight Loss A 2026 systematic review and meta-analysis of randomized controlled trials confirmed that GLP-1 receptor agonists produce clinically meaningful weight loss across diverse patient populations. - Reference: Ahmad H, et al. Medicine. 2026. PMID: 41824845 - URL: https://pubmed.ncbi.nlm.nih.gov/41824845/ ### SURMOUNT-1-4 Nutritional Analysis A post hoc analysis examined nutritional status with tirzepatide in obesity across the SURMOUNT-1-4 randomized clinical trials. - Reference: Almandoz JP, et al. Obesity Pillars. 2026. PMID: 41640675 - URL: https://pubmed.ncbi.nlm.nih.gov/41640675/ --- ## How the Calculator Works 1. **Select Your Medication**: Choose from Ozempic, Wegovy, Mounjaro, Zepbound, or generic semaglutide/tirzepatide. Each medication has a different titration schedule and expected weight loss profile based on clinical trial data. 2. **Enter Your Details**: Input your current weight (lbs or kg), height (ft/in or cm), age, gender, and target weight. The calculator uses these factors alongside published dose-response curves from the STEP and SURMOUNT trial programs. 3. **Get Your Projection**: Receive a week-by-week weight loss chart showing expected progress through each dosing phase, an estimated timeline to reach your goal, the medication's dosing schedule, and personalized calorie, protein, and activity recommendations. --- ## GLP-1 Medication Comparison Table | Medication | Active Ingredient | Mechanism | Avg. Weight Loss | Max Dose | Titration Period | |---|---|---|---|---|---| | Ozempic | Semaglutide | GLP-1 agonist | ~12% | 2.0 mg/week | ~16 weeks | | Wegovy | Semaglutide | GLP-1 agonist | ~15% | 2.4 mg/week | ~16 weeks | | Mounjaro | Tirzepatide | Dual GIP/GLP-1 | ~22% | 15 mg/week | ~20 weeks | | Zepbound | Tirzepatide | Dual GIP/GLP-1 | ~20% | 15 mg/week | ~20 weeks | | Retatrutide | Retatrutide | Triple GIP/GLP-1/Glucagon | ~24% | 12 mg/week | ~12 weeks | --- ## Frequently Asked Questions ### How much weight can you lose on Ozempic (semaglutide)? In the landmark STEP-1 clinical trial, participants receiving semaglutide 2.4 mg once weekly lost an average of 14.9% of their body weight over 68 weeks, compared to 2.4% with placebo. For a 220 lb person, that translates to roughly 33 lbs of weight loss. Individual results vary based on starting weight, adherence, diet, and exercise. (Wilding et al., NEJM, 2021, PMID: 33567185) ### How much weight can you lose on Mounjaro or Zepbound (tirzepatide)? The SURMOUNT-1 trial showed that participants receiving the highest dose of tirzepatide (15 mg) lost an average of 22.5% of their body weight over 72 weeks. This makes tirzepatide-based medications among the most effective weight loss therapies currently available. (Jastreboff et al., NEJM, 2022, PMID: 35658024) ### What is Retatrutide and how much weight loss does it produce? Retatrutide is an investigational triple-action medication that targets the GIP, GLP-1, and glucagon receptors simultaneously. In a phase 2 clinical trial published in the New England Journal of Medicine, participants receiving the 12 mg dose lost an average of 24.2% of their body weight over 48 weeks — the highest weight loss ever recorded for a pharmaceutical agent in clinical trials. Phase 3 trials (the TRIUMPH program) are currently underway. (Jastreboff et al., NEJM, 2023, PMID: 37366315) ### What is the difference between semaglutide and tirzepatide? Semaglutide (Ozempic/Wegovy) is a GLP-1 receptor agonist, while tirzepatide (Mounjaro/Zepbound) is a dual GIP/GLP-1 receptor agonist. Both are administered as once-weekly injections. Clinical trials suggest tirzepatide produces greater average weight loss (up to 22.5%) compared to semaglutide (up to 14.9%), though individual responses vary and both medications are considered highly effective. ### How does the GLP-1 weight loss calculator work? The calculator uses weight loss curves derived from the STEP-1 and SURMOUNT-1 clinical trials combined with your personal data (current weight, height, age, and target weight) to project a personalized week-by-week weight loss timeline. It accounts for the medication's titration schedule to show realistic progress at each dosing stage. ### Are GLP-1 medications safe for weight loss? GLP-1 medications are FDA-approved for chronic weight management. Common side effects include nausea, vomiting, diarrhea, and constipation, which typically improve as the dose is gradually increased. The SELECT cardiovascular outcomes trial also demonstrated that semaglutide reduces the risk of heart attack, stroke, and cardiovascular death in people with obesity and established cardiovascular disease. Always consult your healthcare provider before starting any medication. ### How long does it take to see weight loss results on GLP-1 medications? Most people begin to notice weight loss within the first 4 weeks of treatment. However, significant results typically appear after 3 to 6 months as the medication dose is gradually increased through the titration schedule. Clinical trials show weight loss continues progressively over 12 to 18 months before reaching a plateau at the maintenance dose. ### What happens if I stop taking GLP-1 medication? Research from the STEP-1 trial extension showed that participants regained approximately two-thirds of their lost weight within one year of stopping semaglutide. This underscores the importance of long-term treatment planning and building sustainable lifestyle changes alongside medication use. (Wilding et al., 2022, PMID: 35441470) --- ## Semaglutide (Wegovy) Dosing Schedule - Weeks 1-4: 0.25 mg per week - Weeks 5-8: 0.5 mg per week - Weeks 9-12: 1.0 mg per week - Weeks 13-16: 1.7 mg per week - Week 17+: 2.4 mg per week (maintenance dose) ## Tirzepatide (Mounjaro / Zepbound) Dosing Schedule - Weeks 1-4: 2.5 mg per week - Weeks 5-8: 5.0 mg per week - Weeks 9-12: 7.5 mg per week - Weeks 13-16: 10.0 mg per week - Weeks 17-20: 12.5 mg per week - Week 21+: 15.0 mg per week (maintenance dose) ## Retatrutide (Investigational) Dosing Schedule - Weeks 1-4: 2.0 mg per week - Weeks 5-8: 4.0 mg per week - Weeks 9-12: 8.0 mg per week - Week 13+: 12.0 mg per week (maintenance dose) - Note: Investigational — from phase 2 trial protocol. Phase 3 dosing may differ. --- ## Medical Disclaimer This calculator is intended for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. The weight loss projections are estimates based on average results from published clinical trials and may not reflect your individual experience. GLP-1 medications are prescription drugs that should only be used under the supervision of a qualified healthcare provider. Always consult your doctor before starting, stopping, or changing any medication. --- ## Contact Website: https://www.glp1weightlosscalculator.com