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
100kg in Stone and Lbs — What's a Healthy Weight?
100kg converts to 15 stone and 10 pounds in UK measurements. Whether this weight is healthy for you depends entirely on your height, age, and body composition. The NHS uses BMI (Body Mass Index) as the primary screening tool to assess whether a weight is healthy for your height. Our free BMI calculator above will give you your personal BMI instantly, and we've also included a weight converter to help you track your weight in the units you're most comfortable with. This guide shows you exactly how to understand your weight in the context of NHS health guidelines.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 100kg (15 stone 10lbs), whether your weight is healthy depends on your height. Here are three realistic examples:
- 5ft 8in (173cm): BMI = 30.1 (overweight, just into the obese category). NHS recommends 55–74kg (8st 8lbs–11st 9lbs) as healthy.
- 6ft 0in (183cm): BMI = 29.8 (just overweight). NHS recommends 61–83kg (9st 8lbs–13st 1lb) as healthy.
- 5ft 6in (168cm): BMI = 35.4 (obese). NHS recommends 53–71kg (8st 4lbs–11st 2lbs) as healthy.
The healthy weight range for any height uses the NHS standard: BMI between 18.5 and 24.9. If you're from a South Asian, Chinese, Black African, or Black Caribbean background, the NHS recommends a slightly lower range (18.5–22.9) due to higher health risks at the same BMI. Use our weight converter to check your own height's healthy range, or try the BMI calculator above to get your personal BMI instantly.
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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: When 100kg Needs Action
If 100kg puts you outside the healthy BMI range for your height, the NHS recommends gradual, sustainable weight loss of 0.5–1kg per week. This is typically achieved through a calorie deficit of around 500 kcal per day, combined with increased physical activity.
Waist circumference is also important: men over 94cm (37 inches) and women over 80cm (31.5 inches) have increased health risk, even at a "healthy" BMI. Your GP can assess your individual health and discuss options including lifestyle changes, structured weight loss programmes through the NHS, or in some cases, prescription weight management support. There's no shame in seeking help — sustainable weight loss is a health goal worth pursuing.
- 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.
Is 100kg overweight for everyone?
No. At 100kg, your health depends on your height. At 5ft 8in it may be overweight; at 6ft 2in it could be within a healthy range. Use the BMI calculator above to check your personal BMI, or measure against the NHS healthy weight range for your height shown in the table above.
How do I convert 100kg to stone?
100kg equals 15 stone and 10 pounds (15st 10lbs). To convert kg to stone, divide by 6.35. Our weight converter above makes this instant — just enter your weight and switch between kg, stone, and pounds instantly.
What's the healthy weight range for my height?
The NHS defines healthy BMI as 18.5–24.9. For your specific height, multiply 18.5 by your height in metres squared for the lower bound, and 24.9 by the same for the upper bound. Our free BMI calculator above calculates this automatically — just enter your height and it shows your healthy range in seconds.
How much weight loss would improve my health?
Even a 5–10% reduction in body weight brings real health benefits: lower blood pressure, better blood sugar control, reduced joint pain, and improved sleep quality. At 100kg, losing just 5–10kg can make a measurable difference. Your GP can discuss a realistic, sustainable plan tailored to your health.
Should I see my GP about my weight?
Yes, if you're concerned. Your GP can assess your personal health picture — including blood pressure, cholesterol, family history, and lifestyle — and discuss realistic options. They may recommend NHS weight management support, lifestyle change programmes, or in some cases, referral to specialist services. There's no judgment: weight management is a legitimate health priority.
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.