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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What is 8.4 kg in Stone?
8.4 kilograms is equal to 1 stone and 5.9 pounds (or approximately 1st 6lbs). This conversion uses the standard kilogram to stone conversion rate, where one stone equals 6.35029 kilograms. If you're tracking your weight or comparing measurements across different systems, understanding how to convert kilograms to stone is useful in the UK, where stone remains the preferred unit for body weight on bathroom scales and in everyday conversations. Our free weight converter above makes it simple to check conversions instantly between kg, stone, and pounds.
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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.
Nearby Weight Conversions and Reference Table
To help you understand 8.4kg in context, here are weight conversions for nearby values using the standard kg to stone conversion formula:
- 7.9 kg = 1st 3.6lbs (12.4 lbs)
- 8.1 kg = 1st 4.8lbs (12.8 lbs)
- 8.4 kg = 1st 5.9lbs (13.2 lbs)
- 8.7 kg = 1st 7.1lbs (13.6 lbs)
- 8.9 kg = 1st 8.3lbs (14.0 lbs)
The conversion formula is simple: divide kilograms by 6.35029 to get stone, or multiply by 0.157473. This weight range (around 8–9 kg) is typical for newborns, infants, or small animals, not adult body weight. At average UK adult heights, this weight would result in a significantly underweight BMI reading.
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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 and Healthy Weight Context at 8.4 kg
At 8.4 kg, an individual would be severely underweight according to NHS BMI guidelines, regardless of height. For context, an adult of 1.70m (5ft 7in) at 8.4kg would have a BMI of 2.9, which is far below the NHS healthy weight range of 18.5–24.9. This weight is not typical for adults and may indicate a serious health concern. If you or someone you know is significantly underweight or losing weight unintentionally, it's important to speak with your GP. Use our free BMI calculator above to check your personal BMI and understand your healthy weight range at your own height.
- 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 conversion of 8.4kg to stone and pounds?
8.4 kg equals 1 stone and 5.9 pounds (1st 5.9lbs). This uses the standard stone to kg conversion where 1 stone = 6.35029 kg. You can also express this as approximately 18.5 pounds total, or 1.32 stone.
How do I convert kilos to stone myself?
To convert kilogram to stone conversion, divide the kilogram amount by 6.35029. For 8.4kg: 8.4 ÷ 6.35029 = 1.32 stone. If you need stone and pounds format, multiply the decimal portion by 14 (the number of pounds in one stone).
Is 8.4 kg a healthy weight for an adult?
No, 8.4 kg is not a healthy weight for an adult. This weight would result in a BMI well below 18.5 (underweight) at any adult height. If you're concerned about being underweight or unintentional weight loss, please consult your GP for advice and support.
What is the weight in stone for nearby kilogram values?
Common conversions near 8.4kg: 8.0kg = 1st 4.3lbs, 8.5kg = 1st 6.3lbs, 9.0kg = 1st 8.2lbs, 9.5kg = 1st 10.2lbs. Use our free weight converter on this page to check any kilogram value instantly between kg, stone, and pounds.
Why does the UK still use stone for weight?
Stone has been used in Britain for centuries and remains culturally embedded in UK health and fitness contexts. The NHS uses kilograms clinically, but most UK adults still weigh themselves in stone on bathroom scales. Understanding both systems is useful for health tracking and medical conversations.
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.