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
How to Calculate BMI in kg and cm
BMI (Body Mass Index) is a simple measure of body weight relative to height, calculated using kilograms and centimetres. The standard BMI formula divides your weight in kg by your height in metres squared. In the UK, the NHS uses this metric-based BMI calculation as the primary screening tool for healthy weight ranges. Understanding your BMI in kg and cm is the first step towards assessing your health status and deciding whether you might benefit from lifestyle changes or weight management support.
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 Ranges
The NHS recognises five main BMI categories for UK adults, based on your weight in kilograms and height in centimetres:
- Underweight: BMI below 18.5
- Healthy weight: BMI 18.5 to 24.9
- Overweight: BMI 25.0 to 29.9
- Obese (Class I): BMI 30.0 to 34.9
- Obese (Class II): BMI 35.0 to 39.9
- Severely obese (Class III): BMI 40.0 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 health risks at the same BMI level. A healthy BMI range for these populations is 18.5 to 22.9, with overweight starting at 23.0. You can use our free BMI calculator above to check your personal BMI instantly by entering your weight in kg and height in cm.
Clinically BackedWeight Loss
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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
If your BMI falls outside the healthy range, the NHS offers a structured pathway to support. Your GP can discuss your weight, check for weight-related health conditions, and refer you to appropriate services. The NHS recommends losing weight gradually at 0.5 to 1 kg per week for sustainable results. Tier 1 support includes digital tools and community programmes; Tier 2 includes primary care-based behaviour change support; Tier 3 involves specialist weight management services where medication may be considered. Don't wait for symptoms—early action on excess weight can prevent serious health conditions including type 2 diabetes, heart disease, and certain cancers.
- 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 (metres)². First convert your height from cm to metres by dividing by 100. For example, if you're 170cm tall, convert to 1.70m. Then divide your weight in kg by 1.70 squared. Use our free BMI calculator for gradual improvement without a UK pharmacy calculation.
Is BMI the only measure of healthy weight?
No. The NHS also recommends measuring waist circumference because where fat is stored matters for health. Men over 94cm (increased risk) or 102cm (high risk) waist, and women over 80cm (increased risk) or 88cm (high risk) should discuss health with their GP. BMI doesn't distinguish muscle from fat, so it's one tool among several.
Why does the NHS use different BMI thresholds for some ethnic groups?
Research shows that South Asian, Chinese, Black African, and Black Caribbean populations have higher risk of type 2 diabetes and cardiovascular disease at lower BMI levels. The NHS lowered these thresholds—healthy BMI for these groups starts at 18.5 and overweight at 23.0—to ensure earlier intervention and better health outcomes for high-risk populations.
Should I aim for the lowest BMI in the healthy range?
Not necessarily. A healthy BMI range is 18.5 to 24.9, and anywhere within this range is appropriate for most adults. Your ideal weight depends on factors including age, muscle mass, bone density, and overall fitness. Your GP can advise on a realistic target weight based on your individual health profile.
What should I do if my BMI is in the overweight or obese range?
Contact your GP for a health conversation. They can assess weight-related conditions, discuss lifestyle changes, and if appropriate, refer you to NHS weight management services. Even losing 5 to 10% of your body weight can significantly improve health markers like blood pressure and blood sugar.
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.