GLP-1 Weight Loss Calculator
The average weight loss reported in the clinical trials, matched to your starting weight. Every figure is cited.
GLP-1 Weight Loss Calculator
See the average weight loss reported in the clinical trials for semaglutide, tirzepatide and other GLP-1 medications, matched to your starting weight.
Decimals are fine — 250.4 works
Optional — adds BMI to the results
Grouped by brand. Each one links to the trial that studied it.
Selecting a dose shows what that dose produced in its own clinical trial. It is not a suggestion to take it. Your prescriber determines your dose.
Read this first
These curves are population averages from clinical trials in specific study populations. They are not a personalised medical prediction. Individual results vary substantially — in these trials some participants lost more than 30% of their body weight and some lost none. All trials paired the medication with a reduced-calorie diet and increased physical activity. Consult a healthcare provider for personal guidance.
Average loss in STEP-1 by week 68
14.9%
Equivalent for your starting weight
187.2lbs
Down from 220 — a loss of 32.8 lbs
Trajectory over the trial
Dots mark timepoints the trial published. The line between them is modelled.
Milestones
| Week | Average change | Weight |
|---|---|---|
| 12 | -6.2% | 206.4 lbs |
| 24 | -10.0% | 198.1 lbs |
| 36 | -12.3% | 193 lbs |
| 52 | -14.0% | 189.2 lbs |
| 68 | -14.9%trial data | 187.2 lbs |
How results were spread at week 68
The average above hides a wide range. This is the share of trial participants who reached each level of weight loss.
Where these numbers come from
STEP-1 · Adults with BMI >= 30, or >= 27 with at least one weight-related coexisting condition, WITHOUT type 2 diabetes. · n=1961 · participants started at an average of 232.1 lbs, BMI 37.9.
- European Medicines Agency. Wegovy (semaglutide) EPAR Public Assessment Report, EMA/112307/2022, 11 November 2021. Baseline demographics Table 20 (p.90); STEP 4 run-in week-20 weight loss (p.93); sex subgroup findings (p.123-124).
- ClinicalTrials.gov posted results, NCT03548987 (STEP 4).
- Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384(11):989-1002.
Weight loss in these trials was always alongside a reduced-calorie diet and increased physical activity.
Want the trial data for the other medications?
We send a plain-English breakdown of what the GLP-1 trials actually measured, plus updates when new results are published.
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What this calculator does
Most weight-loss calculators ask you to guess a weekly rate and then multiply it out. This one works the other way round. You pick a medication and dose, and it applies the result that dose actually produced in its clinical trial to your starting weight.
The figures come from the trials themselves — STEP 1 for semaglutide (Wegovy), SURMOUNT-1 for tirzepatide (Zepbound), and the corresponding trials for the other medications listed. Where a trial published an intermediate timepoint, the chart marks it. Where a number had to be worked out from other published figures, the calculator says so. The chart never runs past the period a trial actually studied.
Why the averages look lower than the stories you have read
A 14.9% average over 68 weeks works out to roughly 0.2% of body weight per week. Weight loss in these trials was fastest in the first few months and flattened later, so the weekly figure at the start is higher than the average across the whole trial. The responder breakdown on this page shows the spread behind the average: in SURMOUNT-1, about 63% of participants on 15 mg reached 20% or more, while others lost far less.
What it cannot tell you
It cannot tell you what will happen to you. Trial averages describe a group of people who met specific entry criteria, took the medication under supervision, and followed a reduced-calorie diet and an exercise plan. Individual results in these trials ranged from no weight loss at all to more than 30% of body weight. Talk to a healthcare provider about your own treatment. This page does not give medical advice and does not recommend or adjust doses.