Weight Loss Projection Calculator: Predict Your GLP-1 Results
Enter your current weight, goal, and medication to see a month-by-month projection grounded in published Phase 3 trial data from STEP, SURMOUNT, and ATTAIN. Updated April 2026, medically reviewed by Dr. A. Goher, MD.
Your details
All calculations run locally in your browser — nothing is stored or sent.
FDA-approved specifically for chronic weight management.
Month-by-month projection
Shaded band = realistic range (low to high estimate). Line = expected outcome.
Based on your goals, Mounjaro / Zepbound is your best match
You're aiming to lose 50 lbs (21.7% of your body weight). Dual GIP/GLP-1 agonist — highest average weight loss on the market. Clinical trials show 20-22% average loss, which fits your target.
How this calculator works
Each medication has a documented average weight-loss range from its largest Phase 3 trial: Ozempic 8-14%, Wegovy 15-17%, Mounjaro/Zepbound 20-22%, Foundayo 11-14%, and compounded semaglutide 15-17% (mirroring Wegovy). The calculator averages the low and high ends to create an "expected" line, then plots the full range as a shaded band.
We apply an exponential decay curve — the standard shape observed in real trial data — so most of the loss lands in the first 6-12 months before plateauing. Your diet and exercise selection multiplies the total outcome by 0.85x (minimal), 1.0x (moderate), or 1.15x (high). The "time to goal" figure comes from the first month the expected curve crosses your target weight.
This model is deliberately conservative. Some users will hit their goal faster, and some will not reach it at all — especially if genetics, dose titration, or side effects limit their response. Recent 23andMe research suggests the gap between high and low responders can be 5x.
Frequently asked questions
How accurate is this GLP-1 weight loss calculator?▾
The calculator uses average weight loss percentages from published Phase 3 clinical trials (STEP, SURMOUNT, ATTAIN) and models a realistic plateau curve. It's a useful directional tool, but individual results vary dramatically — anywhere from 0% to 30%+ of body weight — based on genetics, dose, adherence, and lifestyle.
Why does the weight loss curve flatten after 12 months?▾
Clinical data shows most GLP-1 weight loss happens in the first 6-12 months, then plateaus as the body adjusts. Wegovy's STEP 1 trial saw most of the ~15% average loss by month 68. This calculator uses exponential decay to mimic that real-world pattern instead of a straight line.
Which GLP-1 drug gives the most weight loss?▾
Tirzepatide (Mounjaro / Zepbound) currently leads with 20-22% average weight loss in the SURMOUNT trials. Semaglutide (Wegovy, compounded) averages 15-17%. Ozempic, dosed for diabetes, averages 8-14%. Oral orforglipron (Foundayo) averages 11-14% in ATTAIN-1.
Do diet and exercise actually change my projection?▾
Yes. Studies show lifestyle factors can shift total weight loss by 15-30% either direction. High-effort diet and exercise plus a GLP-1 typically outperforms medication alone, while sedentary users may see below-average results. The calculator uses a 0.85x / 1.0x / 1.15x multiplier to reflect this.
What if I stop the medication?▾
Research shows roughly two-thirds of lost weight returns within one year of stopping a GLP-1 without lifestyle intervention. This calculator projects results assuming you stay on the medication and build sustainable habits.
Ready to start losing weight?
See which of the 32 GLP-1 providers we track is the best match for your budget, goals, and medication preference.