GLP-1 Weight Loss Calculator

See a personalized, month-by-month estimate of weight loss on semaglutide (Ozempic, Wegovy) or tirzepatide (Mounjaro, Zepbound), based on the average outcomes reported in the STEP 1 and SURMOUNT-1 clinical trials.

Medical Disclaimer

This calculator is for educational and informational purposes only and does not provide medical advice, diagnose any condition, recommend or prescribe treatment, or guarantee results. Estimates are based on information you provide and published clinical-trial averages. Individual results can vary significantly.

Estimates are based on average outcomes reported in the STEP 1 (semaglutide) and SURMOUNT-1 (tirzepatide) clinical trials. Individual results can vary significantly and are influenced by factors such as dosage, diet, and adherence.

Do not start, stop, or change any medication based on the results of this calculator. Always consult a qualified healthcare professional regarding medications, treatment options, risks, side effects, and your individual health needs.

How this calculator works

You enter your gender, age, current weight, goal weight and the medication you are curious about. The calculator then draws a month-by-month curve from your starting weight toward your goal. The curve rises quickly at first and flattens, the way weight loss did in the trials, and it levels off at the trial average: about 14.9% of starting weight for semaglutide (STEP 1, 68 weeks) and about 20.9% for tirzepatide at the highest dose (SURMOUNT-1, 72 weeks). If your goal is beyond those averages, it says so instead of inventing a date. See how the calculator works for the method and its limits.

What the trials found

Medication	Average loss	Placebo	Length
Wegovy (semaglutide 2.4 mg)	14.9%	2.4%	68 weeks
Zepbound (tirzepatide, 15 mg)	20.9%	3.1%	72 weeks

Those are group averages in adults with obesity or overweight, with diet and activity counseling for everyone. About 83.5% of people on Wegovy and 90.9% on the top Zepbound dose lost at least 5%, so a minority lost less. In SURMOUNT-5, which compared the two directly, tirzepatide averaged 20.2% against 13.7% for semaglutide. Read do GLP-1s work? and semaglutide vs. tirzepatide for the details.

Ozempic, Wegovy, Mounjaro and Zepbound

Semaglutide is the active drug in Ozempic and Wegovy. Wegovy is approved for weight management. Ozempic is approved for type 2 diabetes.
Tirzepatide is the active drug in Zepbound and Mounjaro. Zepbound is approved for weight management. Mounjaro is approved for type 2 diabetes.

See Ozempic vs. Wegovy and Mounjaro vs. Zepbound, or try the semaglutide calculator or the tirzepatide calculator.

Common questions

How long until I see results?

Loss is fastest early and slows toward a plateau. In an analysis of the SURMOUNT-1 tirzepatide trial, the median person reached a plateau at roughly 24 to 36 weeks, depending on starting BMI. See the plateau guide.

Is the calculator accurate?

It applies published group averages to your numbers, so it shows what is typical, not what will happen to you. Dose, diet, activity and staying on treatment all change real results.

Do I need a prescription?

Yes. These are prescription medicines. The FDA advises getting a prescription from your doctor and filling it at a state-licensed pharmacy, and warns about unapproved and compounded versions. See weight loss injections and who the labels cover.

What happens if I stop?

Weight tends to return. In the STEP 1 extension, people regained about two-thirds of what they had lost within a year of stopping. See what happens when you stop a GLP-1.

Popular guides

About this site

The calculator and guides are published by Health Matters USA. Facts come from FDA prescribing information and published trials, which we link on each page. We may receive compensation if you contact or become a customer of a partner referenced on this site, and it does not change the price you pay. Read the about and editorial policy.

Sources