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 Stone in Kilograms?
21 stone is equivalent to approximately 133.2 kg. If you're looking to understand your weight in metric measurements or check where this falls on NHS health guidance, this UK health guide provides the conversion, BMI context, and practical next steps. Whether you're tracking your weight or exploring weight management options, knowing both your stone and kilogram measurements helps you access the full range of NHS health information and resources available to UK adults.
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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.
Converting 21 Stone to Kilograms and Understanding Health Context
21 stone = 133.2 kg (or 133 kg rounded)
To convert stone to kilograms, multiply the stone weight by 6.35029. So 21 × 6.35029 = 133.2 kg. This conversion applies to all weight measurements — whether you're checking your own weight or understanding health data.
At 21 stone (133.2 kg), your health context depends on your height. Use our free BMI calculator above to check your personal BMI instantly — this will show you where your weight sits on NHS guidelines. If you're 5ft 8in (173cm), a weight of 21 stone gives a BMI of approximately 44.9, which falls in the severely obese category. If you're taller, your BMI will be lower; if shorter, it will be higher.
Important: BMI is a useful screening tool but doesn't account for muscle mass or where fat is stored. Your GP can provide personalised health advice based on your individual circumstances.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Weight Management and Next Steps
If you're at 21 stone and concerned about your health, speaking with your GP is a positive first step. Depending on your age, health conditions, and personal goals, your GP may discuss lifestyle changes, referral to NHS weight management services, or in some cases, prescription weight management options.
The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable results. Even a 5–10% reduction in body weight can bring meaningful health benefits, including improved blood pressure, better blood sugar control, and reduced joint strain.
Our free weight converter above lets you track your weight in both stone and kilograms, and our progress tracker helps you log your journey if you decide to make changes. For detailed healthy weight ranges for your height, use the BMI calculator on this page.
- 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 stone to kilograms?
Multiply 21 by 6.35029 to get 133.2 kg. Alternatively, use our free weight converter above — it converts stone to kg instantly for any weight. This metric conversion is the same regardless of your health context.
What does 21 stone mean for my BMI?
Your BMI at 21 stone depends on your height. Use our free BMI calculator above to enter your height and get your exact BMI. If you're around 5ft 8in, you'd have a BMI of roughly 45, which falls in the severely obese NHS category. Your GP can explain what this means for your health.
Is 21 stone overweight?
Yes. According to NHS guidelines, healthy adult weight falls within a BMI of 18.5 to 24.9. At 21 stone, you're above the healthy weight range for all adult heights. Your GP can discuss personalised health advice and whether weight management support would be beneficial for you.
What are my weight management options at 21 stone?
Options range from lifestyle changes (diet and activity) through NHS tier 1–3 weight management services to prescription medication in some cases. Speak with your GP about your circumstances — they can discuss what's right for you. Our progress tracker can help you log changes if you decide to make them.
How much weight would I need to lose to reach a healthy BMI from 21 stone?
It depends on your height. Use our BMI calculator to enter your height and see the healthy weight range for you — this shows exactly how much loss would reach a healthy BMI. The NHS recommends losing 0.5–1 kg per week. Your GP can provide personalised guidance.
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.