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
Am I Obese? Find Out Your BMI Category
If you're concerned about whether you're obese, the NHS defines obesity using BMI (Body Mass Index) — a simple calculation based on your height and weight. An obese BMI is 30 or above according to NHS guidelines, though lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Use our free BMI calculator above to check your personal BMI instantly and see which NHS category you fall into. Your result will tell you whether you're in the healthy weight, overweight, or obese range — and what that means for your health.
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 — Overweight vs Obese
The NHS defines weight categories using BMI ranges. Understanding where you sit helps you make informed health decisions:
- Healthy weight: BMI 18.5–24.9
- Overweight: BMI 25.0–29.9
- Obese (Class I): BMI 30.0–34.9
- Obese (Class II): BMI 35.0–39.9
- Severely obese (Class III): BMI 40.0 and above
However, if you're of South Asian, Chinese, Black African, or Black Caribbean background, the NHS recommends lower thresholds because these groups face higher health risks at the same BMI. For you, an overweight BMI starts at 23.0, and obese begins at 27.5. This doesn't mean you're at greater risk — it reflects that health outcomes differ across populations. The weight converter on this page can help you understand your weight in both metric and imperial measurements.
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.
Waist Measurement — Another Important Check
BMI is useful but doesn't tell the whole story. Waist measurement matters too — where your body stores fat affects your health risk. The NHS also uses waist circumference as a health indicator:
- Men: Over 94cm (37in) = increased risk; over 102cm (40in) = high risk
- Women: Over 80cm (31.5in) = increased risk; over 88cm (34.5in) = high risk
Even if your BMI is in a healthy range, excess abdominal fat can increase cardiovascular risk. Measure your waist at its narrowest point while standing relaxed. If your BMI is in the obese category, or your waist measurement is elevated, speaking to your GP is a sensible next step. They can assess your individual health and discuss options including lifestyle changes, weight management programmes, or in some cases, prescription weight loss support.
- 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 BMI counts as obese in the UK?
According to NHS guidelines, a BMI of 30 or above is classified as obese. However, lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage — for these groups, obese begins at BMI 27.5. Our free BMI calculator above will show you your exact category.
Is BMI overweight the same as obese?
No. Overweight is BMI 25.0–29.9, while obese is BMI 30.0 and above. An overweight BMI means you're above the healthy range but not yet in the obese category. The NHS distinguishes between these because health risks increase at different thresholds.
Can I be obese if I feel healthy?
BMI is a screening tool, not a measure of overall fitness. You might feel well but have an obese BMI. However, obesity is linked to increased risks of type 2 diabetes, heart disease, and other conditions — often without obvious symptoms. Your GP can assess your individual health picture beyond just BMI.
What should I do if my BMI is in the obese range?
Start by discussing your health with your GP. They can assess whether lifestyle changes (diet, activity), NHS weight management programmes, or in some cases prescription medication might help. The NHS offers free support through tier 3 weight management services in many areas. Even a 5–clinically studied weight loss can have real health benefits.
Does waist measurement matter if I know my BMI?
Yes. Waist measurement shows where you carry fat, which affects your health risk independently of BMI. Someone with an obese BMI but healthy waist distribution faces different risks than someone with the same BMI but central obesity. Check both for a complete picture of your health risk.
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.