GLP-1 Weight Loss Calculator
Predict your weight loss journey with Ozempic, Mounjaro, or Zepbound. Estimates based on clinical trial data.
Your Information
Results are estimates only — consult your healthcare provider before making medical decisions.
BMI Change
Detailed Progress Table
| Month | Date | Weight | BMI | Total Lost | % Lost |
|---|---|---|---|---|---|
| Start | Mar 2026 | 220 lbs | 33.5 | — | — |
| 1 | Apr 2026 | 214.7 lbs | 32.7 | -5.3 lbs | 2.4% |
| 2 | May 2026 | 210.3 lbs | 32 | -9.7 lbs | 4.4% |
| 3 | Jun 2026 | 206.6 lbs | 31.4 | -13.4 lbs | 6.1% |
| 6 | Sep 2026 | 198.7 lbs | 30.2 | -21.3 lbs | 9.7% |
| 9 | Dec 2026 | 193.9 lbs | 29.5 | -26.1 lbs | 11.8% |
| 12 | Mar 2027 | 191.1 lbs | 29.1 | -28.9 lbs | 13.1% |
How This Calculator Works
This calculator uses a logarithmic prediction model based on published clinical trial results. Weight loss with GLP-1 medications is typically faster in the early months and gradually plateaus over time.
- Ozempic ~15%: Based on STEP-1 trial data (semaglutide 2.4mg). Actual results with Ozempic (max 2.0mg) may vary.
- Mounjaro / Zepbound (tirzepatide): Average ~22.5% body weight loss over 72 weeks (SURMOUNT-1 trial)
- Diet & exercise only: Estimated ~5% with consistent effort
Individual results vary significantly based on diet, exercise, dosage titration, adherence, and other factors.
How We Predict Your Weight Loss: The Clinical Model
This GLP-1 weight loss calculator uses a logarithmic decay model based on published clinical trial data. Weight loss with GLP-1 medications follows a characteristic curve: rapid reduction in the first 3–6 months that gradually plateaus as the body reaches a new metabolic set point.
The model formula is: Weight(week) = StartWeight × (1 − MaxLoss% × (1 − e−rate × week)). This exponential saturation function closely matches observed trial outcomes and is more accurate than simple linear projections.
Clinical Trial Data: By Medication
| Medication | Trial | Duration | Avg Weight Loss | Top Dose Responders |
|---|---|---|---|---|
| Ozempic (semaglutide 2.0mg) | STEP-1 (2021) | 68 weeks | ~14.9% | Up to 20%+ in some patients |
| Wegovy (semaglutide 2.4mg) | STEP-1 (2021) | 68 weeks | ~15.3% | ~1 in 3 lost 20%+ |
| Mounjaro (tirzepatide 15mg) | SURMOUNT-1 (2022) | 72 weeks | ~22.5% | ~57% lost 20%+ |
| Zepbound (tirzepatide 15mg) | SURMOUNT-1 (2022) | 72 weeks | ~22.5% | ~57% lost 20%+ |
Note: Ozempic's max approved dose is 2.0mg. STEP-1 used 2.4mg (Wegovy dose). Results with Ozempic may be slightly lower than the trial average shown. All figures represent averages; individual results vary significantly.
Why Mounjaro Outperforms Ozempic
Ozempic and Wegovy target only the GLP-1 receptor. Mounjaro and Zepbound (tirzepatide) are dual GIP/GLP-1 receptor agonists — they activate both the glucose-dependent insulinotropic polypeptide (GIP) receptor and the GLP-1 receptor simultaneously. This dual action produces significantly stronger appetite suppression, better glycemic control, and greater total weight loss in head-to-head comparisons.
A 2023 NEJM study (SURMOUNT-4) demonstrated that participants continuing tirzepatide maintained their weight loss, while those switched to placebo regained ~14% of body weight within 52 weeks — confirming the importance of long-term treatment continuity.
Factors That Affect Your Individual Results
Clinical trial averages include a wide range of responders. The following factors can significantly influence how much weight you lose on GLP-1 medications:
- Starting BMI: People with higher starting BMI tend to lose more absolute pounds but similar percentages. Those with BMI 35+ often see the strongest responses.
- Dosage titration: Patients who reach the maximum dose (2.0mg for Ozempic, 15mg for Mounjaro) generally achieve better outcomes. Some cannot tolerate higher doses due to GI side effects.
- Diet quality: GLP-1 medications suppress appetite but don't change food choices. Users who follow a high-protein, lower-carb diet tend to preserve more muscle and lose more fat.
- Exercise (especially resistance training): Adding strength training 2–3x per week significantly improves the fat-to-muscle loss ratio, improving body composition even at the same scale weight.
- Medication adherence: Missed doses reduce efficacy. Weekly injections require consistent scheduling.
- Metabolic factors: Insulin resistance, sleep quality, stress levels, and gut microbiome composition all modulate response.
- Age and sex: Older adults and women on average lose slightly less weight in trials, though absolute benefits remain significant.
- Concomitant medications: Certain antidepressants (SSRIs), corticosteroids, and antipsychotics can blunt weight loss response.
What to Expect Month by Month
GLP-1 weight loss is not linear. Most users experience:
- Month 1–2: Modest loss of 3–7 lbs as the body adjusts. GI side effects (nausea) are most common in this phase.
- Month 3–6: The fastest rate of loss. Most users lose 5–10% of body weight in this window as they reach therapeutic dosing.
- Month 6–12: Loss continues but slows as the body adapts. Emphasis shifts to sustaining the deficit through diet and exercise.
- Month 12+: Many users reach a new plateau. Some require dose adjustments or transition to maintenance strategies.