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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15.8 Stone in Lbs — What's Your BMI?
15.8 stone is approximately 221 pounds in imperial measurements. However, what matters for your health isn't the weight alone — it's your BMI, which depends on both weight and height. At 15.8 stone, your BMI could range from underweight to obese depending on how tall you are. Use our free BMI calculator above to find your personal BMI instantly, or read on to see where 15.8 stone puts you across different heights using NHS guidelines.
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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.
15.8 Stone BMI at Different Heights
Your BMI changes significantly based on your height, even at the same weight. At 15.8 stone (221 lbs), here's what your BMI would be at common UK heights:
- 5ft 2in (157cm): BMI 40.5 — Severely obese (Class III)
- 5ft 5in (165cm): BMI 36.7 — Obese (Class II)
- 5ft 8in (173cm): BMI 33.6 — Obese (Class I)
- 5ft 11in (180cm): BMI 30.8 — Obese (Class I)
- 6ft 1in (185cm): BMI 28.5 — Overweight
- 6ft 4in (193cm): BMI 26.4 — Healthy weight
These calculations use the standard BMI formula: weight in kg divided by height in metres squared. To convert your weight and height more precisely, try our weight converter to switch between kg, stone, and lbs instantly.
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.
Understanding NHS Weight Categories
The NHS divides BMI into clear categories to help assess health risk:
- 18.5–24.9: Healthy weight
- 25.0–29.9: Overweight
- 30.0–34.9: Obese (Class I)
- 35.0–39.9: Obese (Class II)
- 40.0+: Severely obese (Class III)
At 15.8 stone, if your height is below 5ft 11in, your BMI likely falls into the obese range. However, BMI has limitations — it doesn't account for muscle mass or where fat is stored. Your GP can give you personalised advice about what your BMI means for your individual health, especially if you're very muscular or have other health concerns.
- 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 15.8 stone to kg?
To convert stone to kilograms, multiply by 6.35029. So 15.8 stone × 6.35029 = approximately 100.2 kg. You can use our weight converter above for instant conversions between stone, lbs, and kg in any direction.
What does a BMI of 33 mean?
A BMI of 33 falls into the "Obese (Class I)" category according to NHS guidelines. This means your health risk from excess weight is elevated. Your GP can advise on whether weight management would benefit your health.
Is BMI accurate for muscular people?
No. BMI doesn't distinguish between muscle and fat, so very muscular individuals may have a high BMI despite low body fat. If you're concerned about your BMI result, discuss it with your GP or check your waist circumference — the NHS recommends measuring waist to assess health risk too.
Can I lose weight from 15.8 stone safely?
Yes. The NHS recommends losing no more than 0.5–1 kg (1–2 lbs) per week for sustainable results. This typically requires a calorie deficit of around 500 kcal per day. Your GP can help you create a safe plan tailored to your health.
What's the healthy weight range for my height?
The healthy BMI range is 18.5–24.9. To find your healthy weight range, multiply 18.5 × your height (m)² for the lower bound, and 24.9 × your height (m)² for the upper bound. Use our free BMI calculator to check your personal healthy weight range instantly.
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.