GLP-1 weight loss calculator
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See what the average person's weight did, week by week, in the main trials, applied to your starting weight.
Enter your numbers
Weeks are the trial's visits. Values are read from regulators' published charts and rounded to whole percents. This is not medical advice.
How it works
- Choose a trial and dose. The tool has the average percent change at each trial visit.
- Your starting weight × that percent gives the same change on your weight.
- The placebo line shows what happened without the medicine in the same trial.
What these numbers are
- Who was in the trials. Adults with obesity or overweight, without diabetes, who also had diet and activity support.
- Doses went up in steps. SURMOUNT-1 reached 5, 10 and 15 mg at weeks 4, 12 and 20. STEP 1 reached 2.4 mg at week 16.
- Tirzepatide curve. It counts people while they stayed on treatment, so it runs higher than the main trial result. The main result, counting everyone, was −15.0%, −19.5% and −20.9% at week 72.
- Semaglutide curve. It uses observed data during the trial. The main result, with missing data estimated, was −14.9% at week 68.
Do not use this tool to compare the two medicines. The curves were measured differently and the trials were separate.
How much people varied
| Group | Lost under 5% | Lost 15% or more | Lost 20% or more |
|---|---|---|---|
| Tirzepatide 5 mg | 14.9% | 48.0% | 30.0% |
| Tirzepatide 10 mg | 11.1% | 66.6% | 50.1% |
| Tirzepatide 15 mg | 9.1% | 70.6% | 56.7% |
| Placebo, SURMOUNT-1 | 65.5% | 8.8% | 3.1% |
| Semaglutide 2.4 mg | 16.5% | 47.9% | 30.2% |
| Placebo, STEP 1 | 68.9% | 4.8% | 1.7% |
At the trial's end, counting everyone randomised, from the Zepbound and Wegovy labels. Tirzepatide at week 72 and semaglutide at week 68.
Frequently asked questions
Will I lose this much?
Nobody can say. These are averages, and the table above shows how widely people varied.
Why does the curve flatten?
Weight loss slowed in the trials. FDA reviewers describe a plateau around week 60 on both medicines. EMA reviewers say tirzepatide's higher doses seemed to continue through week 72.
Why is retatrutide not here?
As of 2 November 2026 we found no approval from any regulator, so we keep it out of this tool. See the retatrutide page.
Why are these numbers different from other calculators?
Trials report several versions of the same result, depending on how they count people who stopped. We say which one each curve uses.
- Tirzepatide weekly values: read from Figure 11 of the EMA Mounjaro assessment report. Week 72 matches the figures printed there.
- Semaglutide weekly values: read from Figure 9 of the FDA Wegovy clinical review, to about ±0.2 points. Week 68 matches ClinicalTrials.gov.
- Main results and shares: Zepbound and Wegovy labels on DailyMed. Checked 2 November 2026.
Related pages
See your own curve instead
Reko charts your real weight beside your doses, so you can see what is actually happening to you.