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
BMI Calculator — Understanding Your Healthy Weight Range
A BMI calculator helps you understand whether your weight is in a healthy range according to NHS guidance. BMI (body mass index) is a simple screening tool that uses your height and weight to assess your health risk. The NHS uses standardised BMI categories to help you and your GP determine if you're at increased risk from weight-related health conditions. Our free BMI calculator above gives you an gradual improvement, but understanding what your BMI means — and its limitations — is just as important as the number itself.
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.
NHS BMI Categories and Healthy Weight Ranges
The NHS recommends a healthy BMI range of 18.5 to 24.9 for most UK adults. Your BMI is calculated by dividing your weight in kilograms by your height in metres squared — this is the standard BMI formula used across the UK health system. The NHS BMI categories are:
- Below 18.5: Underweight
- 18.5–24.9: Healthy weight
- 25.0–29.9: Overweight — associated with increased health risks
- 30.0–34.9: Obese (Class I)
- 35.0–39.9: Obese (Class II)
- 40.0 and above: Severely obese (Class III)
However, if you are of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — a healthy BMI range of 18.5 to 22.9 applies to you, because these communities face higher health risks at lower BMI levels. Use our free BMI calculator above to find your personal BMI instantly.
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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.
NHS Weight Management Pathway — When to Seek Help
If your BMI falls outside the healthy range, the NHS offers a structured weight management pathway with four tiers of support. Tier 1 includes self-help digital tools and community programmes; Tier 2 involves your GP and behaviour change support; Tier 3 is specialist multidisciplinary weight management services where prescription medications like Mounjaro or Wegovy may be prescribed; and Tier 4 is bariatric surgery for severe obesity. Your GP can assess whether you qualify for specialist support based on your BMI and any weight-related health conditions like type 2 diabetes or high blood pressure. Remember, BMI has limitations — it doesn't account for muscle mass, where fat is stored, or individual differences — so your GP will consider your overall health picture, not just your BMI number.
- 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 healthy BMI range according to the NHS?
The NHS recommends a healthy BMI of 18.5 to 24.9 for most UK adults. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, the recommended range is 18.5 to 22.9, because these communities have higher cardiovascular and diabetes risk at lower BMI levels.
How do I calculate my BMI?
BMI = weight (kg) ÷ height (metres)². For example, if you weigh 70kg and are 1.73m tall, your BMI = 70 ÷ (1.73 × 1.73) = 23.4. Our free BMI calculator above does this instantly — just enter your weight and height.
What should I do if my BMI is outside the healthy range?
Contact your GP for a health assessment. They can discuss your individual circumstances, check for weight-related health conditions, and refer you to the appropriate NHS support. This might include Tier 2 behaviour change programmes or Tier 3 specialist weight management services depending on your BMI and health.
Why does the NHS have different BMI thresholds for some ethnicities?
Research shows that South Asian, Chinese, Black African, and Black Caribbean populations face higher risks of type 2 diabetes and heart disease at lower BMI levels compared to European populations. The NHS uses ethnicity-adjusted thresholds to ensure fair and accurate health risk assessment across all communities.
What are the limitations of BMI?
BMI doesn't distinguish between muscle and fat — athletes may have a high BMI but low body fat. It also doesn't account for where fat is stored (belly fat is riskier than other areas) or age-related muscle loss. Your GP will consider BMI alongside waist circumference, blood pressure, and other health markers for a complete picture.
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.