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
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How to Calculate BMI Using Kg and Cm
BMI (Body Mass Index) is calculated using a simple formula: your weight in kilograms divided by your height in metres squared. This metric-based approach is the standard used by the NHS and healthcare professionals across the UK. Understanding how to calculate your BMI using kg and cm helps you determine whether your weight falls within a healthy range for your height. Our free BMI calculator above can instantly calculate this for you, but it's useful to understand the maths behind it and what your result means for your health.
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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 Calculation Using Metric Measurements
The BMI formula using kg and cm is straightforward: BMI = weight (kg) ÷ height (m)². To use this correctly, you must first convert your height from centimetres to metres by dividing by 100. For example, if you are 170cm tall, that equals 1.70 metres. If you weigh 75kg, your BMI calculation is: 75 ÷ (1.70 × 1.70) = 75 ÷ 2.89 = 26.0.
Once you have your BMI number, you can compare it against the NHS BMI categories, which apply to most UK adults:
- Below 18.5 = Underweight
- 18.5 to 24.9 = Healthy weight
- 25.0 to 29.9 = Overweight
- 30.0 to 34.9 = Obese (Class I)
- 35.0 to 39.9 = Obese (Class II)
- 40.0 and above = Severely obese (Class III)
These thresholds are based on NHS guidance and represent established health risk levels for the general UK population.
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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 Limitations and What Else Matters
While BMI is a useful screening tool, it has important limitations. It does not distinguish between muscle and fat — so athletes or people with high muscle mass may have a high BMI despite low body fat. BMI also ignores where fat is stored; waist circumference is equally important for assessing health risk. The NHS recommends measuring waist circumference alongside BMI: men over 94cm face increased cardiovascular risk, and women over 80cm face similar increases.
Additionally, if you are of South Asian, Chinese, Black African, or Black Caribbean heritage, your health risk at the same BMI is higher. The NHS recommends lower thresholds for these groups: healthy weight is 18.5 to 22.9 rather than 18.5 to 24.9. Your GP can provide personalised guidance about what your BMI and measurements mean for your individual health.
- 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 exact BMI formula using kg and cm?
The formula is BMI = weight (kg) ÷ height (m)². Convert your height from centimetres to metres by dividing by 100, then square that figure and divide your weight by it. For example, 75kg at 1.70m = 75 ÷ 2.89 = BMI of 26.0.
What BMI range is considered healthy according to the NHS?
The NHS defines healthy BMI as between 18.5 and 24.9 for most UK adults. However, 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 higher BMI levels.
Can I use the BMI formula with just metric measurements?
Yes, the metric BMI formula (kg and metres) is the standard used by the NHS and most healthcare professionals. It's simpler than imperial conversions. Use our free BMI calculator above to compute your result instantly without a UK pharmacy calculations.
What does a BMI of 27 mean in UK health terms?
A BMI of 27 falls in the overweight category (25.0–29.9) according to NHS guidelines. While not yet in the obese range, the NHS recommends lifestyle changes to prevent further weight gain and reduce health risks. Your GP can advise on personalised steps.
Is BMI alone enough to assess my health?
No. BMI should be used alongside waist circumference measurement and other health markers. A high BMI combined with a large waist circumference indicates greater health risk. Your GP can assess your overall health picture and recommend appropriate support or monitoring.
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.