Expected weight loss calculator: Mounjaro vs Wegovy

Our Expected Weight Loss Calculator uses average results from landmark clinical trials to project how much weight you may lose on Mounjaro (tirzepatide) or Wegovy (semaglutide) over your chosen timeframe, based on your starting weight. Enter your details above to generate a personalised estimate in seconds. These figures are averages drawn from trial data and individual results will vary, but the calculator can help you set realistic, evidence-based expectations before or during treatment.

How the Expected Weight Loss Calculator works

The Expected Weight Loss Calculator draws on percentage body weight loss data published in two pivotal trials: the SURMOUNT-1 trial for Mounjaro (tirzepatide 15 mg) and the STEP 1 trial for Wegovy (semaglutide 2.4 mg). In SURMOUNT-1, participants lost an average of approximately 20.9% of their body weight over 72 weeks, while STEP 1 participants lost an average of around 14.9% over 68 weeks. The calculator applies these weekly average rates proportionally to your starting weight and your chosen treatment duration to produce a projected figure.

It is important to understand that these percentages represent mean outcomes from tightly controlled clinical trials conducted in adults with obesity or overweight plus at least one weight-related condition. Real-world results depend on many individual factors, including adherence to the recommended dose escalation schedule, dietary habits, physical activity levels, and underlying health conditions. The calculator gives you a useful ballpark — not a guarantee.

Factors that affect your expected weight loss results

While the Expected Weight Loss Calculator provides a data-driven projection, a number of personal and lifestyle factors mean your actual progress may be faster or slower than the average. Understanding these variables can help you interpret your estimate more accurately and work with your prescriber to optimise your treatment plan.

• Starting weight and BMI — people with a higher starting BMI often see greater absolute weight loss in kilograms, even if the percentage is similar.
• Dose and escalation — both Mounjaro and Wegovy are titrated gradually; spending longer at lower doses due to tolerability may affect early progress.
• Diet and calorie intake — clinical trials pair medication with a reduced-calorie diet; following dietary guidance significantly improves outcomes.
• Physical activity — regular exercise supports fat loss, preserves lean muscle mass, and can enhance the medication's effect.
• Metabolic health — conditions such as type 2 diabetes, hypothyroidism, or polycystic ovary syndrome (PCOS) can influence how quickly weight responds to treatment.
• Medication adherence — missing doses or discontinuing treatment early will reduce overall weight loss compared with trial averages.
• Biological sex and age — hormonal differences and age-related metabolic changes can affect the rate and extent of weight loss.
• Gut microbiome and genetics — emerging research suggests individual biological variation plays a meaningful role in GLP-1 receptor agonist response.

What your Expected Weight Loss Calculator result actually means

Once the Expected Weight Loss Calculator has generated your projection, it is worth taking a moment to understand what that number represents in practical health terms — and what it does not tell you.

Interpreting your projected weight and health milestones

Even a modest reduction of 5–10% of starting body weight is associated with clinically meaningful improvements in blood pressure, blood glucose regulation, cholesterol levels, and joint health, according to NICE guidance on obesity management. If your calculator result falls in this range over a shorter duration, that still represents a significant health benefit — not a disappointing outcome. Framing progress around health markers, rather than purely a number on the scales, tends to support better long-term motivation.

For longer durations, the calculator may project losses of 15% or more of body weight. Research published in journals such as The New England Journal of Medicine suggests that losses of this magnitude are associated with remission of type 2 diabetes in some patients, substantial reductions in cardiovascular risk, and improvements in obstructive sleep apnoea. Your GP or prescriber can help you understand which specific health goals are most relevant to your situation and how to track progress beyond the scales — for example, through waist circumference measurements, HbA1c readings, or blood pressure monitoring.

Using your Expected Weight Loss Calculator estimate to plan next steps

Your Expected Weight Loss Calculator projection is a starting point for an informed conversation with a healthcare professional — not a standalone treatment plan. If you are not yet on a weight loss medication and the estimate suggests meaningful potential benefit, speaking to a GPhC-registered online pharmacy or your GP about eligibility for Mounjaro or Wegovy is a sensible next step. NICE guidance (TA875 for tirzepatide and TA875 predecessor guidance for semaglutide) sets out the criteria for NHS and private prescribing, including BMI thresholds and the requirement for specialist weight management support.

If you are already taking one of these medications and your actual progress is significantly below the projected average, do not be discouraged without first reviewing the full picture. Plateaus are common, particularly around weeks 12–20, and may respond to dose escalation, dietary adjustment, or increased physical activity. Cured Pharmacy's clinical team can discuss your progress and whether your current treatment plan is optimised. Equally, if you are losing weight faster than projected, it is still important to maintain regular check-ins to monitor for any nutritional deficiencies or other considerations that can accompany rapid weight loss.

Frequently Asked Questions

Sources

1. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1) The New England Journal of Medicine [accessed 26 August 2026]
2. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1) The New England Journal of Medicine [accessed 26 August 2026]
3. NICE Technology Appraisal TA875: Tirzepatide for managing overweight and obesity National Institute for Health and Care Excellence (NICE) [accessed 26 August 2026]
4. NICE Technology Appraisal TA664: Semaglutide for managing overweight and obesity National Institute for Health and Care Excellence (NICE) [accessed 26 August 2026]
5. Obesity: identification, assessment and management (Clinical Guideline CG189) National Institute for Health and Care Excellence (NICE) [accessed 26 August 2026]
6. Weight management: BMI and waist circumference thresholds NHS England [accessed 26 August 2026]
7. Cardiovascular, mortality, and kidney outcomes with GLP-1 receptor agonists in patients with type 2 diabetes The Lancet Diabetes & Endocrinology [accessed 26 August 2026]
8. Association of bodyweight changes with mortality in patients with obesity PubMed / National Library of Medicine [accessed 26 August 2026]
9. Weight management services for adults: commissioning guide NHS England [accessed 26 August 2026]
10. Obesity and weight management — overview British Nutrition Foundation [accessed 26 August 2026]

This calculator provides an estimate for general informational purposes only and is not medical advice. Always consult a qualified healthcare professional before making changes to your diet or starting any weight loss treatment.