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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Convert 8st 9lbs to Kilograms
8 stone 9 pounds (8st 9lbs) converts to approximately 55 kilograms (kg) using the standard UK to metric conversion. Stone and pounds remain the most common way UK adults discuss body weight, whilst kilograms are used in NHS health measurements and clinical settings. Understanding both measurements helps you access NHS guidance, track your health using the weight converter on this page, and communicate effectively with your GP about your weight and health goals.
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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.
How to Convert 8st 9lbs to Kilograms
To convert 8 stone 9 pounds to kilograms, use this straightforward calculation: multiply the stone weight by 6.35029, then add the pounds converted to kilograms (pounds × 0.453592). For 8st 9lbs: (8 × 6.35029) + (9 × 0.453592) = 50.80 + 4.08 = approximately 55 kg.
The exact conversion is 54.98 kg, commonly rounded to 55 kg in health and NHS contexts. This conversion matters because NHS health assessments, clinical guidelines, and many UK weight management services use kilograms as the standard measurement. Use our free weight converter above to switch between stone, pounds, and kilograms instantly for any weight value.
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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.
Is 8st 9lbs a Healthy Weight in the UK?
Whether 55 kg is a healthy weight depends on your height, age, sex, and ethnic background. The NHS uses BMI (body mass index) to assess healthy weight ranges. At 55 kg, your BMI varies significantly by height: for example, someone 160cm tall would have a BMI of around 21.5 (healthy range), whilst someone 175cm tall would have a BMI around 18 (also healthy). Use our free BMI calculator on this page to check your personal BMI and see where you fall within NHS guidelines. If you have concerns about your weight or health, your GP can provide personalised advice based on your individual circumstances and medical history.
- 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 8st 9lbs in kilograms exactly?
8 stone 9 pounds equals 54.98 kg, which rounds to 55 kg in NHS and health contexts. The conversion uses: (8 × 6.35029) + (9 × 0.453592) = 55 kg approximately.
Is 55 kg a healthy weight?
Healthy weight depends on height, age, and sex. Use our BMI calculator to find your personal BMI. At 55 kg, adults of average UK height (around 170cm) typically fall within or near the NHS healthy weight range of 18.5–24.9 BMI. Your GP can advise on what's healthy for you.
Why does the NHS use kilograms instead of stone?
Kilograms are the international standard measurement used in medical records, clinical trials, and NHS health guidelines. Stone remains common in everyday UK conversation, but healthcare professionals use kg for accuracy and consistency across health systems.
How do I convert other weights from stone to kilograms?
Divide the total weight in pounds by 2.20462 to get kg, or use the formula: (stone × 6.35029) + (pounds × 0.453592) = kg. Our free weight converter on this page converts any weight instantly between stone, pounds, and kilograms.
Can I use this conversion for health tracking?
Yes, understanding your weight in both stone and kilograms helps you track progress and communicate with your GP. If you're managing your weight, use our free progress tracker to log your weight in either measurement, and our BMI calculator to monitor your health context alongside the numbers.
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.