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
What Measurement Unit Is BMI? UK Explained
BMI (Body Mass Index) is measured as kilograms per square metre, written as kg/m². This is the standard measurement unit used by the NHS and health services worldwide. BMI is calculated by dividing your weight in kilograms by your height in metres squared. Understanding the BMI measurement unit and how it works helps you interpret your personal BMI result and what it means for your health according to UK guidelines.
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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.
How BMI Is Calculated and Measured
BMI is always measured in kg/m² — kilograms per square metre — regardless of whether you use metric or imperial measurements in everyday life. The BMI formula is simple: weight (kg) ÷ height (m)². For example, if you weigh 70kg and are 1.75 metres tall, your BMI would be 70 ÷ (1.75 × 1.75) = 22.9 kg/m².
The NHS uses this standardised measurement unit so doctors and healthcare professionals can compare your result consistently. Even if you prefer to think about your weight in stone and pounds, your healthy BMI range remains the same: 18.5 to 24.9 kg/m² for most UK adults. Use our free BMI calculator above to find your personal BMI instantly — it converts between units automatically and shows you where you fall within the NHS bmi categories uk.
Different ethnic groups have adjusted BMI range UK thresholds. South Asian, Chinese, Black African, and Black Caribbean adults should use lower thresholds: 18.5 to 22.9 kg/m² for healthy weight, reflecting higher health risks at higher BMI levels within these communities.
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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.
BMI Measurement Limitations and Complementary Measures
While BMI limitations are important to understand, BMI remains a useful screening tool. BMI does not distinguish between muscle and fat — athletes may have a high kg/m² result but low body fat percentage. It also ignores where fat is stored, yet abdominal fat carries greater health risks than fat stored elsewhere.
The NHS recommends using BMI alongside other measurements for a complete picture: waist circumference (over 94cm in men or 80cm in women suggests increased risk), and overall lifestyle factors. Use our free weight converter and bmi calculator together to understand your weight in both metric and imperial units, then discuss your individual health with your GP, who can assess whether your BMI measurement and your overall health profile require any action or monitoring.
- 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 does kg/m² mean in BMI measurement?
kg/m² (kilograms per square metre) is the standard unit for BMI used globally by the NHS and health organisations. It represents your weight in kilograms divided by your height in metres squared. This standardised measurement allows doctors to compare health risks consistently across populations.
Why does the NHS use kg/m² instead of other units?
The kg/m² unit is the international standard because it accounts for both weight and height proportionally. It's used by the WHO, NHS, and health systems worldwide, making it easy to compare health data across countries and populations reliably.
Does BMI measurement change if I use stone instead of kilograms?
No. Your BMI result in kg/m² is the same regardless of whether your weight is recorded in kilograms, stone, or pounds. The measurement unit (kg/m²) never changes — only your weight input format changes. Your health category remains identical.
Is BMI measurement accurate for everyone?
BMI is a useful screening tool but has limitations. It doesn't distinguish muscle from fat, so athletes may have a high BMI despite low body fat. It also ignores where fat is stored and may be less accurate for elderly people or very tall/short individuals.
What's the healthy BMI measurement range according to the NHS?
For most UK adults, healthy BMI is 18.5 to 24.9 kg/m². For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower range: 18.5 to 22.9 kg/m². Your GP can advise on your individual healthy target based on your medical history.
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.