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 is 21.8kg in Stone?
21.8kg is equal to 3 stone and 6.4 pounds (3st 6.4lbs). This is a straightforward kg to stone conversion using the standard UK measurement system. At this weight, your health context depends significantly on your height — the same weight can represent very different BMI values for different adults. Use our free weight converter above to check conversions between kilograms, stone, and pounds instantly, and then use our BMI calculator to see where this weight sits for your specific height and age.
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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.
21.8kg to Stone Conversion Chart
To convert kilograms to stone, divide the kilogram value by 6.35029. For 21.8kg: 21.8 ÷ 6.35029 = 3.43 stone, which equals 3 stone and 6.4 pounds. This conversion formula works for any weight in stone and pounds.
Here's a reference table showing 21.8kg alongside nearby weight values:
- 19kg = 2st 13.2lbs
- 20kg = 3st 2.1lbs
- 21kg = 3st 5.1lbs
- 21.8kg = 3st 6.4lbs
- 22kg = 3st 7lbs
- 23kg = 3st 9.9lbs
- 24kg = 3st 12.8lbs
For quick reference: 1 kilogram equals 0.157473 stone, and 1 stone equals exactly 14 pounds.
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.
Is 21.8kg a Healthy Weight?
Whether 21.8kg is healthy depends entirely on your height, age, and body composition. At this weight, you would be classified as significantly underweight according to NHS guidelines for most adults. A healthy BMI sits between 18.5 and 24.9 for the general population, though lower thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage.
For example, at an average UK adult height of 170cm (5ft 7in), a weight of 21.8kg would result in a BMI of approximately 7.5 — well below healthy range. If you're concerned about being underweight, your GP can assess your individual health and offer appropriate guidance. Use our BMI calculator on this page to find your personal BMI instantly.
- 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.
How do I convert 21.8kg to stone and pounds?
Divide 21.8 by 6.35029 to get 3.43 stone. Multiply 0.43 by 14 to get 6.4 pounds. So 21.8kg = 3 stone 6.4 pounds. Our free weight converter above can do this instantly for any weight value.
What is 21.8kg in just pounds?
21.8kg equals approximately 48 pounds (21.8 × 2.20462 = 48.02 lbs). This is useful if you need the pound-only measurement without stone conversion.
Is 21.8kg underweight?
At 21.8kg, you would be significantly underweight for virtually any adult height according to NHS guidelines. Healthy weight depends on height — use our BMI calculator to check your personal BMI. If concerned about your weight, speak to your GP.
Can I use this conversion for children's weight?
This conversion formula works for any weight value, but remember that healthy weight ranges are very different for children. Children use age and sex-specific growth charts, not adult BMI categories. Always consult your health visitor or GP for children's weight guidance.
Why do UK people use stone and pounds?
Stone is a traditional UK and Irish measurement unit. Most UK adults are familiar with stone for body weight, even though NHS clinical records use kilograms. Both systems are equally valid — conversion tools like ours help bridge between them.
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.