What this calculator estimates
This tool projects your potential weight loss on each GLP-1 by applying that drug’s average clinical-trial result to your current weight. It’s the fastest way to see the difference between the medications in real pounds rather than abstract percentages, and to set a realistic expectation before you start.
The key word is average. Every number here comes from a large clinical trial, and in those trials some people lost dramatically more than the average while others lost relatively little.
That is why the calculator no longer shows a single “range most people fall in”. It used to, and the range was not real: its two ends were the average results of two different dose groups, which says nothing about how widely individuals varied. What the trials do publish is a responder table, so the calculator now shows that instead. In SURMOUNT-1, 91% of people on 15 mg tirzepatide lost at least 5% of their body weight and 84% lost at least 10%. Those are counts of actual participants, and they are a far better answer to “what might I get” than any band we could draw.
The trial numbers behind it
Each medication’s estimate is anchored to its main study:
| Medication | Average loss | Trial |
| Drug | Lost on the drug | Lost on placebo | Difference the drug made | Trial |
|---|---|---|---|---|
| Zepbound (tirzepatide 15 mg) | 20.9% | 3.1% | 17.8 points | SURMOUNT-1, 72 weeks |
| Wegovy injection (semaglutide 2.4 mg) | 14.9% | 2.4% | 12.5 points | STEP 1, 68 weeks |
| Foundayo (orforglipron 17.2 mg) | 11.1% | 2.1% | 9.0 points | label Trial 1, 72 weeks |
| Saxenda (liraglutide 3 mg) | 7.4% | 3.0% | 4.4 points | label Study 1, 56 weeks |
Read the middle column before the first one. Everyone in these trials got diet and exercise support, and the placebo groups still lost 2 to 3 per cent. The last column is what the drug itself added. Both numbers are true, and quoting only the first makes every one of these drugs look stronger than it is.
These are four separate trials in different populations, not a head-to-head. Ranking drugs across them is an indirect comparison, so treat small gaps as noise.
The diabetes-approved GLP-1s are not in this table on purpose. Ozempic and Rybelsus report weight change in kilograms rather than as a percentage of body weight, and our evidence base carries no weight-loss figure at all for Victoza or Trulicity. Rather than convert or estimate, the calculator says so and declines to forecast them.
* Mounjaro, Ozempic, Rybelsus, Victoza, and Trulicity are FDA-approved for type 2 diabetes, not weight loss, and the calculator gives a figure for none of them. Mounjaro used to borrow Zepbound’s SURMOUNT-1 result, a trial that excluded people with diabetes. Weight loss is consistently smaller in people who have type 2 diabetes, so that number would have flattered the drug for the people actually taking it.
Two things stand out. First, tirzepatide leads, and its 17.8-point advantage over placebo is territory that used to require surgery. Second, the same molecule can behave very differently by product and dose: Wegovy and Ozempic are both semaglutide, but they were studied at different doses in different populations, which is why only one of them appears above.
Why your real result will differ
A calculator can’t know your biology, so treat the output as a reasonable expectation, not a promise. The biggest factors that move you within (or beyond) the range:
- Dose reached. The trial averages assume you titrate up to and stay at the studied maintenance dose. People who stop climbing early tend to lose less.
- Time. These results unfold over 12–18 months, not weeks. The early months are dose-ramp months.
- Diet, protein, activity, and sleep. The trials paired the drug with lifestyle support for a reason. The medication works best as a floor for your appetite, not a replacement for the basics. Protecting muscle with enough protein also shapes how good the loss looks and feels.
- Consistency and staying on it. Trial extensions show much of the weight returns after stopping, so durability depends on maintenance.
Using it well
Use this to compare medications and set expectations, then track reality against it with the weight-loss percentage calculator once you start. If the numbers make a GLP-1 feel worth exploring, the next questions are whether you qualify and how to get one. A licensed provider decides what’s appropriate for you. This tool is educational and not medical advice.