The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
Free Health Calculators for UK Adults
MyWeightCheck provides free, easy-to-use health calculators designed specifically for UK measurements and NHS guidelines. Whether you need to convert your weight between kg and stone, calculate your BMI, explore potential weight loss outcomes with GLP-1 medication, or track your progress over time, our suite of tools gives you instant, personalised health information. All calculators are based on evidence-based NHS guidance and updated clinical data. No registration required — simply enter your details and get your results immediately.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
What Health Calculators Are Available on MyWeightCheck?
MyWeightCheck offers four core free calculators to support your health and weight management journey:
- BMI Calculator — Calculate your Body Mass Index and see where you fall on the NHS healthy weight scale. Includes ethnicity-adjusted thresholds for South Asian, Chinese, Black African, and Black Caribbean adults, who have different health risk profiles at the same BMI.
- Weight Converter — Convert between kilograms, stone, and pounds instantly. UK adults often prefer stone, so our converter makes switching between metric and imperial measurements seamless.
- GLP-1 Weight Loss Calculator — If you're considering or taking prescription weight loss medication such as Mounjaro or Wegovy, this calculator helps estimate potential weight loss outcomes based on clinical trial data. Results vary between individuals.
- Progress Tracker — Log your weight regularly and visualise your progress over weeks and months. Tracking supports motivation and helps identify trends in your weight management journey.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Why Use Evidence-Based Health Calculators?
Self-assessment tools are most helpful when they reflect real NHS guidelines and clinical evidence. Our calculators use established NHS thresholds for healthy weight ranges, STEP and SURMOUNT clinical trial data for GLP-1 projections, and UK-specific measurements (stone and pounds) that match how most British adults think about weight. This means results are immediately relevant and actionable. Using a personalised health guide — whether that's understanding your BMI, exploring weight loss options with your GP, or simply tracking your progress — helps you make informed decisions about your health without relying on guesswork or generic online tools.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Are MyWeightCheck calculators accurate?
Yes. All calculators use evidence-based formulas aligned with NHS guidelines and published clinical trial data. BMI uses the standard World Health Organization formula; GLP-1 projections are based on STEP (Wegovy) and SURMOUNT (Mounjaro) trial outcomes. Individual results vary, so use calculators as guides, not assures. For personalised advice, consult your GP.
Do I need to create an account to use the calculators?
No. All MyWeightCheck calculators are completely free and require no registration, login, or email. Simply visit the page, enter your details, and get gradual improvement. Your data is not stored or shared.
What's the difference between BMI and body composition?
BMI measures weight relative to height and is a useful screening tool. However, it doesn't distinguish between muscle and fat — athletes may have high BMI but low body fat. Body composition analysis looks at actual muscle versus fat percentage, which is more detailed but requires specialist equipment like DEXA scans.
Can the GLP-1 weight loss calculator predict my exact weight loss?
No. The calculator shows average outcomes from clinical trials, but individual results vary significantly based on genetics, lifestyle, dose adherence, diet, and exercise. Clinical trials showed average weight loss of 15–21% with Mounjaro and approximately 15% with Wegovy, but your personal outcome depends on many factors.
Should I use these calculators instead of seeing my GP?
No. These calculators are informational tools to help you understand your health better, not replacements for professional medical advice. Always consult your GP if you're concerned about your weight, have health conditions, or are considering prescription weight loss medication.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.