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
Track Your Body Measurements in Centimetres
A CM tracker helps you monitor body measurements like waist, chest, and hip circumference — often a better indicator of progress than weight alone. Many people find that measuring centimetres reveals real changes that the scales don't show, especially when combined with exercise. Our free progress tracker on MyWeightCheck lets you log measurements over time and spot trends. This is particularly useful if you're following a weight management plan, whether through lifestyle changes or prescription medication like Mounjaro or Wegovy.
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.
Why Measure in Centimetres Instead of Just Weight?
Weight alone doesn't tell the full story. Two people at the same weight can look and feel completely different depending on muscle mass, fat distribution, and where weight sits on the body. Waist circumference is especially important because fat stored around the stomach carries greater health risks than fat elsewhere.
According to NHS guidance, healthy waist measurements are:
- Men: under 94cm (37 inches) — increased risk above this
- Women: under 80cm (31.5 inches) — increased risk above this
When you're following a weight loss programme or taking weight management medication, centimetre measurements often change faster than weight. This is because you may be building muscle while losing fat — the scale stays flat, but your measurements shrink. Tracking both weight and measurements gives you a complete picture of real progress and helps maintain motivation.
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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.
How to Measure Accurately and Track Progress
For consistent measurements, measure at the same time of day (mornings are best), in the same clothing (or minimal clothing), and using the same tape measure. Key measurements to track include:
- Waist: at belly button level, relaxed (not sucked in)
- Chest: at the fullest point, across the nipples
- Hips: at the widest point around the buttocks
- Thigh: mid-thigh, above the knee
Our free progress tracker lets you log these measurements weekly or monthly, compare changes over time, and celebrate non-scale victories. Combined with your BMI using our free BMI calculator, measurement tracking gives you a comprehensive view of your health progress.
- 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.
What's the difference between measuring weight and measuring centimetres?
Weight shows total body mass but doesn't distinguish between muscle, fat, and water. Centimetre measurements track fat loss specifically and show where your body is changing. Someone losing fat while building muscle may see stable weight but shrinking measurements — a sign of real progress.
Why do some people measure progress in cm instead of kg?
Measurements can change faster than weight, especially when exercising. If you're building muscle, you might lose fat (shrinking measurements) while weight stays the same. This helps people stay motivated and see results that scales don't reflect.
Is waist measurement really important for health?
Yes. NHS guidance emphasises waist circumference because excess belly fat increases risk of type 2 diabetes and heart disease, even in people with a healthy BMI. Measuring waist is a simple health check alongside weight and BMI.
How often should I measure myself?
Weekly or monthly is ideal — any more frequently and natural daily fluctuations can be discouraging. Aim for the same day and time each week, in similar conditions, to get comparable measurements.
Can I track measurements alongside weight loss medication?
Absolutely. If you're taking Mounjaro, Wegovy, or following any weight loss plan, tracking measurements alongside weight gives you a fuller picture of progress. Use our free progress tracker to log both.
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.