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
How Height and Weight Affect Your BMI
Your height and weight together determine your BMI (body mass index), which is a screening tool used by the NHS to assess whether you're in a healthy weight range. BMI is calculated by dividing your weight in kilograms by your height in metres squared. Understanding how these two measurements work together helps you make sense of your health and whether you fall into a healthy BMI range for your age and background.
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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.
BMI Formula and NHS Categories
The BMI formula is straightforward: weight (kg) ÷ height (m)². For example, someone who is 1.73m tall weighing 70kg would have a BMI of approximately 23.4, which falls in the healthy range. The NHS uses these BMI categories UK: below 18.5 is underweight, 18.5–24.9 is healthy weight, 25–29.9 is overweight, 30–34.9 is obese class I, 35–39.9 is obese class II, and 40+ is severely obese. However, these thresholds differ for adults of South Asian, Chinese, Black African, or Black Caribbean heritage — the healthy BMI range for these groups starts at 18.5 and extends only to 22.9, reflecting higher health risks at standard weights. Use our free BMI calculator above to determine your personal BMI instantly based on your exact height and weight.
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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.
Understanding BMI Limitations and Context
While the BMI formula is useful, it has significant limitations. BMI does not distinguish between muscle and fat — an athlete with high muscle mass may have a high bmi range uk but low body fat. Similarly, BMI doesn't account for where fat is stored; bmi limitations mean it's not a complete health picture. The NHS recommends checking your waist circumference alongside BMI: over 94cm (37 inches) for men or 80cm (31.5 inches) for women indicates increased health risk. Your GP can discuss your personal health context and whether BMI is the right measure for you.
- 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 is the BMI formula and how do I calculate it?
BMI equals your weight in kilograms divided by your height in metres squared. For example: if you weigh 65kg and are 1.65m tall, your BMI is 65 ÷ (1.65 × 1.65) = 23.9. Use our free BMI calculator above for gradual improvement — it handles the maths for you automatically.
What is the healthy BMI range according to the NHS?
The NHS defines a healthy BMI as 18.5 to 24.9 for most adults. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is 18.5 to 22.9 due to higher health risks at standard weights. Your GP can advise what's healthy for your individual circumstances.
Does a high BMI always mean you're unhealthy?
Not necessarily. BMI has important limitations — it doesn't distinguish muscle from fat, so very muscular individuals may have a high BMI but excellent health. BMI also doesn't account for age, bone density, or where fat is stored. Always discuss your personal health with your GP rather than relying on BMI alone.
How does height affect BMI if weight stays the same?
Height has a squared effect on BMI, so small height differences significantly impact results. For example, 70kg at 1.60m gives a BMI of 27.3 (overweight), but 70kg at 1.75m gives a BMI of 22.9 (healthy). Taller individuals can carry more weight while maintaining a healthy BMI range.
What should I do if my BMI falls outside the healthy range?
If your BMI is outside the healthy range, discuss this with your GP. They can assess your overall health, medical history, and individual circumstances. The NHS offers support through weight management services, which may include behaviour change programmes, dietary advice, and in some cases prescription treatment or specialist referral.
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.