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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21.3 Stone In Kg — What Does This Weight Mean For Your Health?
21.3 stone is equal to approximately 135.2 kilograms. Whether this weight is healthy for you depends entirely on your height, age, and individual circumstances. The NHS uses BMI (Body Mass Index) to assess weight health, and at the same weight, someone who is 5ft 4in might fall into the obese category, whilst someone who is 6ft 3in might fall into the overweight category. Use our free BMI calculator above to find out where your personal weight sits on the NHS health scale.
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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.
Healthy Weight Ranges At Different Heights
At 21.3 stone (135.2kg), whether you're in a healthy weight range depends on your height. Here are three realistic examples showing how the same weight translates to very different health assessments:
- At 5ft 4in (163cm): 135.2kg gives a BMI of 45.4 — this falls into the severely obese category. The healthy range at this height is 47–63kg (7st 6lbs to 9st 13lbs).
- At 5ft 10in (178cm): 135.2kg gives a BMI of 19.4 — this falls into the healthy weight range. The healthy range at this height is 54–72kg (8st 6lbs to 11st 5lbs).
- At 6ft 2in (188cm): 135.2kg gives a BMI of 18.2 — this is well within the healthy range. The healthy range at this height is 57–77kg (8st 13lbs to 12st 2lbs).
To convert kilograms to stone and find your healthy weight range instantly, use the weight converter and BMI calculator on this page.
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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 Guidance: Waist Measurement Also Matters
BMI is a useful screening tool, but the NHS also recommends checking your waist circumference, as this indicates where fat is stored — and abdominal fat carries greater health risks. Healthy waist measurements: men under 94cm (37in), women under 80cm (31.5in). If your BMI falls outside the healthy range or your waist measurement is high, your GP can offer personalised advice. Weight management through sustainable dietary changes and increased physical activity is recommended by the NHS. If you're concerned about your weight or health, speak to your GP — they can assess your individual circumstances and discuss whether additional support, such as a structured weight management programme, might help.
- 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 21.3 stone in kilograms?
21.3 stone equals approximately 135.2 kilograms. To convert stone to kilogram to stone accurately, use the standard conversion: one stone equals 6.35kg. You can also use our free weight converter above to switch between stone, pounds, and kilograms instantly.
Is 21.3 stone a healthy weight?
It depends on your height. At 5ft 4in, this weight is in the severely obese range. At 5ft 10in, it's in the healthy range. At 6ft 2in, it's well within healthy limits. Use our BMI calculator to check your personal BMI and see where your weight falls on the NHS health scale.
How many stone and pounds is 135.2kg?
135.2kg converts to 21 stone and 4.2 pounds (or 21.3 stone when expressed as a decimal). To convert kilograms to stone and pounds, divide the kilogram amount by 6.35 for stone, then multiply the remainder by 14 for pounds.
What should I do if my weight is outside the healthy range?
Speak to your GP, who can assess your individual health. They may recommend a structured weight management programme, dietary advice, or increased physical activity. The NHS offers free resources including the weight loss plan. Your GP can also check your waist measurement and discuss any weight-related health conditions.
What's the healthy weight range at my height?
Healthy weight varies by height. At 5ft 4in, it's 47–63kg (7st 6lbs to 9st 13lbs). At 5ft 10in, it's 54–72kg (8st 6lbs to 11st 5lbs). At 6ft 2in, it's 57–77kg (8st 13lbs to 12st 2lbs). Use our BMI calculator above to find your specific healthy range based on your exact height.
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.