How much weight do people lose on average?

In trials, semaglutide averaged about 15% of body weight and tirzepatide about 20%, over roughly 68 weeks. Individuals vary widely.

Is this a prediction of my results?

No. It applies trial averages to your numbers. Your actual loss depends on dose, adherence, lifestyle, and biology.

Why does the loss level off?

Weight loss on these drugs tends to slow and plateau over many months, which the 16-month ramp reflects.

Can I use this to decide on medication?

No. It is informational only. Decisions about GLP-1 medications must be made with a qualified prescriber.

What's the difference between the two drugs?

They are different medications with different average results and side-effect profiles. A clinician can advise on suitability.

Can I share a calculation?

Yes. Use Share to copy a link that reopens the calculator with the same inputs.

GLP-1 weight loss calculator

Enter your starting weight, choose semaglutide or tirzepatide, and set the months on treatment. The calculator projects a weight using the average loss seen in trials. It is informational only — your real results will differ and treatment must be supervised.

Use it to see roughly how trial-average GLP-1 weight loss could look over time — never as medical advice.

Projected weight

92.5 kg

Weight lost: 7.5 kg
Loss percentage: 7.5%

The result updates as you type. The headline is the projected weight; the others show the weight lost and the loss as a percentage of your start weight.

How does it work?

These are averages from clinical trials, not a personal prediction. Real results depend on dose, diet, activity, and individual response. Always follow a prescriber — this tool is informational only.

GLP-1 weight-loss projection

\text{loss}\% = \text{target} \times \min\!\left(1, \tfrac{m}{16}\right)

loss%: Projected loss as a percentage of start weight.
target: Average plateau loss: 15% semaglutide, 20% tirzepatide.
m: Months on treatment (ramps over ~16).

At 100 kg on semaglutide for 8 months: 15% × (8/16) = 7.5%, about 7.5 kg lost, projecting 92.5 kg.

Method & sources

Average plateau loss: about 15% on semaglutide, 20% on tirzepatide. Loss ramps roughly linearly toward the plateau over about 16 months. These are trial averages, not a personal prediction.

Sources

Where this method comes from — use these references to understand the formula, assumptions, and limits.

Prescription medications to treat overweight and obesity — U.S. National Institute of Diabetes and Digestive and Kidney Diseases, verified 2026-06-10

How we calculate

Average plateau loss: about 15% on semaglutide, 20% on tirzepatide.
Loss ramps roughly linearly toward the plateau over about 16 months.
These are trial averages, not a personal prediction.
Informational only — treatment must be guided by a prescriber.

Rounding

Weights are shown to one decimal. The calculation uses full precision.

What this calculator does

GLP-1 medications like semaglutide and tirzepatide produced substantial average weight loss in clinical trials. This calculator scales those averages by your time on treatment to project a weight. It is a rough illustration of the trial averages, not a forecast for any individual.

How to use it

Enter your starting weight.
Choose the medication.
Set how many months you've been (or will be) on treatment.
Read the projected weight and loss.

A worked example

At 100 kg on semaglutide for 8 months, the model applies 15% × (8/16) = 7.5%, about 7.5 kg lost, projecting 92.5 kg. By 16 months it approaches the full 15% average.

Why your results will differ

Trial averages hide a wide range. Dose, how long you stay on treatment, diet, activity, and individual biology all shape the real outcome. Some people lose much more, others much less.

Important safety note

These medications are prescription-only and have risks and side effects. This tool does not give medical advice or dosing. Any treatment must be started and supervised by a qualified prescriber.

When it's useful

For a rough sense of the scale of average GLP-1 weight loss over time — as background for a conversation with a clinician, not a personal plan.

FAQ

How much weight do people lose on average?: In trials, semaglutide averaged about 15% of body weight and tirzepatide about 20%, over roughly 68 weeks. Individuals vary widely.
Is this a prediction of my results?: No. It applies trial averages to your numbers. Your actual loss depends on dose, adherence, lifestyle, and biology.
Why does the loss level off?: Weight loss on these drugs tends to slow and plateau over many months, which the 16-month ramp reflects.
Can I use this to decide on medication?: No. It is informational only. Decisions about GLP-1 medications must be made with a qualified prescriber.
What's the difference between the two drugs?: They are different medications with different average results and side-effect profiles. A clinician can advise on suitability.
Can I share a calculation?: Yes. Use Share to copy a link that reopens the calculator with the same inputs.

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<p>Calculator from <a href="https://wisecalcs.com/en/health/glp1-weight-loss-calculator">WiseCalcs</a></p>