GLP-1 Weight Loss Calculator: Wegovy, Zepbound, Mounjaro

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Formula at a glance

GLP-1 Weight Loss Calculator: Expected weight — start × (1 − trial average % × progress by week). Example: 100 kg on tirzepatide 15 mg for 52 weeks → Average expected weight after 52 weeks: 79.9 kg — How the GLP-1 Weight Loss Calculator works: Expected weight — start × (1 − trial average % × progress by week)

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📘 About the GLP

GLP-1 medicines reduce appetite. In their main trials, people on semaglutide 2.4 mg lost 14.9% of body weight on average after 68 weeks, and people on tirzepatide 15 mg lost 20.9% after 72 weeks. Most of the loss happens in the first year, then it levels off.

This tool applies those average curves to your starting weight. Real results vary widely — some lose much more, some much less — and depend on diet, activity and dose. It is educational only and cannot tell you which medicine or dose is right; that is a decision for your doctor.

🧮 Formula

Expected weight

start × (1 − trial average % × progress by week)

✏️ Worked examples

100 kg on tirzepatide 15 mg for 52 weeks

You enter
Units	Metric (kg, cm)
Starting weight	100
Height (optional, for BMI)	170
Medication (trial)	Tirzepatide 15 mg (Zepbound / Mounjaro)
Weeks on treatment	52 weeks

You get
Average expected weight after 52 weeks	79.9 kg
Average loss	20.1 kg (20.1%)
Trial result	20.9% average loss at week 72
Based on	Tirzepatide 15 mg weekly (Zepbound/Mounjaro) — SURMOUNT-1
BMI	34.6 → 27.6

79.9 kg on average.

250 lb on semaglutide 2.4 mg for 68 weeks

You enter
Units	Imperial (lb, inches)
Starting weight	250
Height (optional, for BMI)	66
Medication (trial)	Semaglutide 2.4 mg weekly (Wegovy)
Weeks on treatment	68 weeks

You get
Average expected weight after 68 weeks	212.8 lb
Average loss	37.3 lb (14.9%)
Trial result	14.9% average loss at week 68
Based on	Semaglutide 2.4 mg weekly (Wegovy) — STEP 1 trial
BMI	40.4 → 34.3

212.8 lb on average.

🧭 How to use this calculator

What you enter

Units
Starting weight
Height (optional, for BMI)
Medication (trial)
Weeks on treatment (weeks)

What you get

Average expected weight after 52 weeks
Average loss
Trial result
Based on
BMI

❓ Frequently asked questions

How much weight can you lose on Wegovy?

In the STEP 1 trial, an average of 14.9% of body weight over 68 weeks, alongside diet and exercise advice.

How much weight can you lose on Zepbound or Mounjaro?

In SURMOUNT-1, an average of 15% (5 mg), 19.5% (10 mg) and 20.9% (15 mg) over 72 weeks.

How fast does GLP-1 weight loss happen?

Gradually: doses start low and increase over months; loss is fastest in the first 6–9 months and plateaus around a year to 18 months.

What happens when you stop?

Trials show most people regain a large part of the weight within a year of stopping.

📉 GLP-1 Weight Loss Calculator (Wegovy, Zepbound, Mounjaro)