Weight loss calculator · trial averages
GLP-1 Weight Loss Calculator: Trial Averages
Apply average weight changes from FDA label trials to a starting weight. See each medicine next to its own placebo arm, with the share of people reaching several weight loss thresholds.
Last updated Medical review in progress
These are averages from clinical trials, not a prediction for you. Many people lost more or less. Your prescriber decides whether a medicine fits you and at what dose.
Trial average estimator
Start with your weight
Enter a starting weight to apply each label reported average to your weight. The math uses the same starting weight for every arm so the trial results are easy to read side by side.
Enter a weight from 88.2 lb to 771.6 lb (40 kg to 350 kg). Enter a starting weight to see the trial averages.
How to read this page
The primary trial labels report results for all randomized participants, using each label's own method for missing data. The populations were adults with obesity, or adults with overweight with at least one weight-related condition, without type 2 diabetes for the main trials. They ran for 68 weeks, 64 weeks, 72 weeks, 72 weeks.
The calculator applies each label reported mean percentage change to the starting weight you enter. It does not rewrite your input while you type. Switching units shows the converted value, with pounds as whole numbers and kilograms to one decimal place, while keeping the exact weight for calculations. Average losses are displayed in whole pounds or to one decimal kilogram. Threshold amounts are shown to one decimal place with “about.”
Trials differ in who took part, how long they ran and how they were analyzed, so compare a medicine with its own placebo, not with other trials.
The Foundayo label says the trials used an investigational orforglipron formulation, shown as equivalent Foundayo dosages. The table uses the label dose names.
Trials with type 2 diabetes
These separate label trials had smaller average changes. They are shown for context and are not used by the calculator above.
| Medicine and study | Length | Arm | Mean change | N |
|---|---|---|---|---|
| Wegovy injection Study 3, STEP 2 | 68 weeks | Wegovy 2.4 mg once weekly injection | −9.6% | 404 |
| Placebo | −3.4% | 403 | ||
| Zepbound Study 2, SURMOUNT-2 | 72 weeks | Zepbound 10 mg once weekly | −12.8% | 312 |
| Zepbound 15 mg once weekly | −14.7% | 311 | ||
| Placebo | −3.2% | 315 | ||
| Foundayo Trial 2 | 72 weeks | Foundayo 5.5 mg once daily | −5.1% | 329 |
| Foundayo 9 mg once daily | −7% | 332 | ||
| Foundayo 17.2 mg once daily | −9.6% | 322 | ||
| Placebo | −2.5% | 630 |
Mean change is the label reported average for each arm. The placebo rows are included so you can read each trial in context.
What the spread means
The trial tables also show the share of people who lost at least 5%, 10%, 15% or 20% of body weight. The calculator turns those thresholds into amounts for your starting weight. For example, the 83.5% in the Study 2 table means that share of people reached at least 5% loss in that trial arm.
Common questions
How much weight will I lose on semaglutide?
You cannot know in advance. In the 68 week STEP 1 trial, the Wegovy injection average was −14.9% of starting weight. Many people lost more or less. Talk with your prescriber about whether it fits you.
Does the calculator predict my weight loss?
No. It applies a trial average to the starting weight you enter. It does not predict what will happen to you. Your result may be higher or lower, and your prescriber decides whether a medicine fits you.
Sources: Wegovy (semaglutide) US Prescribing Information, Zepbound (tirzepatide) US Prescribing Information, Foundayo (orforglipron) US Prescribing Information
Why does the page show placebo?
The placebo arm helps you read the trial in context. Compare each medicine with its own placebo because the trials differed in who took part, how long they ran and how they were analyzed.
Sources: Wegovy (semaglutide) US Prescribing Information, Zepbound (tirzepatide) US Prescribing Information, Foundayo (orforglipron) US Prescribing Information
Why are the trial lengths different?
The primary trials ran for 68 weeks, 64 weeks, 72 weeks, 72 weeks. Results from different trials are not head to head results.
Sources: Wegovy (semaglutide) US Prescribing Information, Zepbound (tirzepatide) US Prescribing Information, Foundayo (orforglipron) US Prescribing Information
What should I do with these numbers?
Use them as a way to understand the label tables, not as a treatment plan. Your prescriber decides whether a medicine fits you and at what dose.
Sources: Wegovy (semaglutide) US Prescribing Information, Zepbound (tirzepatide) US Prescribing Information, Foundayo (orforglipron) US Prescribing Information
Keep learning
Read the dose calculators and label-based math pages.
Sources
The medical and device facts on this page come from these sources. Each entry shows the date we accessed it.
- 01 Wegovy (semaglutide) US Prescribing Information · Novo Nordisk, 06/2026. Accessed 2026-09-28.
- 02 Zepbound (tirzepatide) US Prescribing Information · Eli Lilly, 08/2026. Accessed 2026-09-28.
- 03 Foundayo (orforglipron) US Prescribing Information · Eli Lilly, 07/2026. Accessed 2026-10-01.