GLP-1 Weight-Loss Calculator: Project Your Results

Few questions matter more to someone considering a GLP-1 medication than the simplest one: how much weight will I lose? The honest answer is that no one can tell you your number in advance. What can be said, and said with real evidence behind it, is what people lost on average in the large randomized trials that brought these drugs to market. Those averages are a far better anchor than the transformation stories that circulate online, which are selected precisely because they are unusual.

How to use this calculator

In the tool above, enter your starting weight and choose a medication. The calculator applies that drug's average trial result to your weight and returns a projected total loss, a target weight, and an illustrative trajectory across the first several months. Switch between metric and imperial units with the toggle. Treat the output as a grounded estimate, not a promise, for reasons the rest of this page makes clear.

Where the numbers come from

The projections are built on the pivotal phase 3 trials. For semaglutide 2.4 mg, marketed as Wegovy, the STEP 1 trial recorded an average total body-weight loss of about 14.9 percent over 68 weeks. For tirzepatide, marketed as Zepbound and Mounjaro, the SURMOUNT-1 trial recorded about 20.9 percent at the 15 mg dose over 72 weeks. Liraglutide, an earlier daily GLP-1 sold as Saxenda, averaged closer to 8 percent. When the two leading drugs were compared directly in the SURMOUNT-5 trial, tirzepatide came out ahead, roughly 20 percent against 14 percent. The fuller picture, drug by drug, is laid out in our breakdown of weight-loss results by drug, and the two leaders are compared in semaglutide versus tirzepatide.

Why your result will not be the average

An average conceals an enormous spread. In the semaglutide trial, some participants lost more than a quarter of their body weight while others lost very little, and the same wide scatter appeared for tirzepatide. Several things move an individual along that range: the maintenance dose actually reached, since results climb with dose; how consistently the medication is taken; and the diet and activity changes made alongside it, because the drug lowers appetite but does not choose your food. Starting weight matters too, as the percentage is applied to a larger or smaller base. A sober framing of what to expect for yourself is offered in our guide to realistic weight-loss goals on a GLP-1.

Weight loss is a slope, not a switch

The trajectory matters as much as the endpoint. Weight does not drop the day you start; it comes off over many months as the dose is titrated upward and appetite settles into a lower set point. In the trials, the steepest decline occurred in the first several months, gradually flattening toward a plateau somewhere between roughly twelve and seventeen months in. The interim milestones the calculator shows are an illustration of that shape rather than exact per-drug figures, because the published data report the endpoint far more precisely than the month-by-month path. The real pace, and what to expect at each stage, is mapped in our GLP-1 weight-loss timeline.

The number the calculator cannot show: what happens after

A projection of loss is only half the story. Because these medications work by suppressing appetite rather than permanently resetting the body's weight regulation, stopping them is typically followed by partial regain, a pattern seen clearly when trials extended past the point of discontinuation. That does not make the loss meaningless; it means the durable outcome depends on either continued treatment or the habits, especially around food and muscle-preserving protein, built while on the drug. It also underscores why the mechanism, not just the headline percentage, is worth understanding before starting, a theme we take up in GLP-1 versus traditional weight loss.

A tool, not a prescription

Use this calculator to replace fantasy with a realistic range, and to see that even the average result is clinically significant: a 15 to 20 percent loss is far beyond what diet and exercise alone typically sustain, and enough to shift blood pressure, blood sugar, and joint load. But the figure it produces is a starting point for a conversation with a clinician who knows your history, not a plan in itself. What you do with the appetite window the medication opens is what turns a projection into a result.