GLP-1 weight loss calculator
See what the average person in the big trials lost, applied to your starting weight, and whether you’re ahead of or behind that average.
Short answer
In the main trials, people lost on average 14.9% of their starting weight on semaglutide 2.4 mg (Wegovy) over 68 weeks and 15–21% on tirzepatide (Mounjaro, Zepbound) over 72 weeks, depending on dose. Enter your starting weight to see what that average looks like for you at 12, 26 and 52 weeks. It’s an average, not a prediction.
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Where the numbers come from
| Trial | Medicine and dose | Average weight lost | At week |
|---|---|---|---|
| STEP 1 (2021) | Semaglutide 2.4 mg (Wegovy) | 14.9% | 68 |
| SURMOUNT-1 (2022) | Tirzepatide 5 mg | 15.0% | 72 |
| SURMOUNT-1 | Tirzepatide 10 mg | 19.5% | 72 |
| SURMOUNT-1 | Tirzepatide 15 mg | 20.9% | 72 |
| Both | Placebo | 2.4–3.1% | 68–72 |
Averages are for adults with obesity or overweight without diabetes, who also had diet and activity counselling. Ozempic’s approved doses for type 2 diabetes go up to 2 mg, and people with diabetes tend to lose less. The curve between the start and the trial end is our approximation of the published curves, which fall fastest in the first 20–30 weeks and flatten after about a year.
The part the scale doesn’t show
In DXA substudies, roughly 25–40% of the weight lost was lean mass, not fat. Strength training and enough protein are the two things most clinicians mention. The scale can’t tell you which you’re losing; your waist next to your arm and shoulder measurements, and matched photos, can. ProgressLens was built for this: its AI report includes a muscle-loss signal. See the GLP-1 progress tracker.
See also: Ozempic, Mounjaro, Zepbound: fat or muscle? · GLP-1 progress month by month · Mounjaro progress tracker
FAQ
Frequently asked questions
How much weight will I lose on Ozempic?
At the 2.4 mg dose (Wegovy) the STEP 1 trial average was 14.9% of starting weight at 68 weeks. With lower diabetes doses (Ozempic), people usually lose less. Your result can be very different from the average.
How much weight do you lose on Mounjaro in a month?
In SURMOUNT-1 the average was roughly 2–3% of bodyweight a month in the first few months, slowing after that. Enter your starting weight to see the curve.
Is Mounjaro better than Ozempic for weight loss?
In trials, tirzepatide led to more average weight loss than semaglutide; the SURMOUNT-5 head-to-head trial (2025) found about 20% vs 14% at 72 weeks. Which suits you is a question for your prescriber.
Why am I losing less than the average?
In STEP 1, about a third of people on semaglutide lost less than 10%. Dose, time on the full dose, diet and other medicines all matter. Talk to your prescriber; don’t change your dose yourself.
Will I lose muscle on a GLP-1?
Some lean mass loss is expected with any large weight loss. Strength training 2–3 times a week and enough protein reduce it. Track it with the fat vs muscle calculator.