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 in Stone — NHS UK Weight Categories Explained
BMI (Body Mass Index) is a screening tool that uses your weight in stone and your height to assess whether you're in a healthy weight range according to NHS guidelines. Understanding your BMI is important because it helps identify health risks associated with excess weight. This guide explains how BMI works in stone, what the NHS considers a healthy BMI, and how to interpret your personal BMI result using UK measurements and NHS thresholds.
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 BMI range divides adults into five categories based on their BMI score. A healthy BMI is between 18.5 and 24.9 — this range indicates a lower risk of weight-related health problems. If your weight in stone places you at a BMI of 25 to 29.9, you fall into the overweight category. A BMI of 30 or above is classified as obese, and the NHS BMI categories break this further into three classes: Class I (30–34.9), Class II (35–39.9), and Class III (40 and above).
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds because these groups face higher cardiovascular and diabetes risks at the same BMI. Their healthy range is 18.5 to 22.9, and overweight begins at 23. Use our free BMI calculator above to instantly check your personal BMI and see which category applies to you.
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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 and When to Seek Help
The NHS weight management pathway has four tiers. Tier 1 includes self-help and digital tools — like our free weight converter and progress tracker — to help you manage weight independently. Tier 2 involves primary care-based support from your GP, including behaviour change programmes. Tier 3 is specialist multidisciplinary weight management services, where prescription weight loss treatment may be considered. Tier 4 is bariatric surgery for severe obesity with significant health complications.
Your GP can advise which tier suits you and refer you onward if needed. Even modest weight loss of 5–10% can improve blood pressure, blood sugar control, and reduce joint strain. The NHS emphasises sustainable approaches combining dietary changes with increased physical activity.
- 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.
How do I convert my weight in kg to stone and then calculate BMI?
Convert kg to stone by dividing by 6.35 — for example, 70kg ÷ 6.35 = 11 stone. Then use the BMI formula: weight (kg) ÷ height (m)². Our free weight converter and BMI calculator do this instantly for you using UK measurements, so you can see both your weight in stone and your BMI result in seconds.
What BMI is considered healthy according to NHS guidelines?
The NHS defines a healthy BMI as 18.5 to 24.9 for most UK adults. For South Asian, Chinese, Black African, or Black Caribbean adults, the threshold is slightly lower: 18.5 to 22.9. Your GP can tell you whether you're in the healthy range and discuss any health implications of your personal BMI.
Why does the NHS have different BMI thresholds for certain ethnic groups?
Research shows that people of South Asian, Chinese, Black African, and Black Caribbean heritage develop type 2 diabetes and cardiovascular disease at lower BMI levels than European populations. The NHS adjusted thresholds to reflect this increased risk, ensuring fairer and more accurate health screening across all ethnic groups in the UK.
What are the limitations of BMI as a health measure?
BMI limitations include that it doesn't distinguish muscle from fat — athletes may have high BMI but low body fat. BMI also ignores where fat is stored and doesn't account for age-related muscle loss or pregnancy. Your GP may assess waist circumference and other factors alongside BMI for a fuller health picture.
Should I contact my GP if my BMI falls into the overweight or obese category?
Yes. If your BMI is 25 or above (or 23 or above for South Asian/Black African/Caribbean/Chinese adults), it's worth discussing with your GP. They can assess your individual health, identify any weight-related conditions, and recommend appropriate support — which might include lifestyle changes, tier 2 programmes, or referral to specialist services.
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.