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's 123 Kg in Stone and What Does Your BMI Mean?
123 kg converts to approximately 19 stone 5 lbs in UK measurements. However, your BMI — and which NHS weight category you fall into — depends on your height. At 123 kg, your BMI could range from around 21 to over 35, depending on whether you're 6 feet tall or shorter. Use our free BMI calculator above to find your personal BMI instantly, or see the examples below to understand how height changes everything about your weight health assessment.
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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.
123 Kg BMI at Different Heights
123 kg is a substantial weight, but whether it's healthy depends entirely on your height. Here's how your BMI changes across typical UK heights:
- At 5ft 4in (163cm): BMI = 32.7 — falls in the Obese (Class I) category
- At 5ft 7in (170cm): BMI = 30.5 — falls in the Obese (Class I) category
- At 5ft 10in (178cm): BMI = 28.1 — falls in the Overweight category
- At 6ft 0in (183cm): BMI = 26.1 — falls in the Overweight category
- At 6ft 2in (188cm): BMI = 24.4 — falls in the Healthy weight category
As you can see, the same weight produces very different BMI values depending on height. Taller people have lower BMI at the same weight. To convert 123 kg to stone precisely: divide 123 by 6.35029, giving you 19.37 stone — or 19 stone 5 lbs in UK measurements.
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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 BMI Categories and What They Mean
The NHS uses standard BMI categories for adults to assess weight-related health risk. A BMI below 18.5 is underweight; 18.5–24.9 is a healthy weight; 25–29.9 is overweight; and 30 and above indicates obesity. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds due to higher health risks at these weights. Remember that BMI is a useful screening tool but has limitations — it doesn't account for muscle mass, bone density, or where fat is stored. Your GP can give you personalised advice about what your specific BMI means for your health. Use our weight converter to check other weights, or try our GLP-1 weight loss calculator if you're exploring weight management options.
- 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 123 kg in stone exactly?
123 kg equals 19 stone 5 lbs (or 19.37 stone). To convert kg to stone, divide the kilogram amount by 6.35029. This standard conversion is used across the UK for health records and personal weight tracking. You can verify this using our free weight converter above.
Is 123 kg overweight or obese?
Whether 123 kg is overweight or obese depends on your height. At 5ft 7in, it gives a BMI of 30.5 (obese). At 6ft 2in, it gives a BMI of 24.4 (healthy weight). Use the BMI calculator on this page with your exact height to find your personal category.
What's the healthy weight range for someone at 5ft 10in?
At 5ft 10in (178cm), a healthy BMI weight range is approximately 59–79 kg (9st 4lbs to 12st 6lbs). At 123 kg, you're above this range. Your GP can discuss personalised weight targets based on your health, not just BMI alone.
Can BMI be inaccurate?
Yes. BMI doesn't distinguish between muscle and fat — athletes may have high BMI but low body fat. It also doesn't account for age, bone density, or where fat is stored. Waist circumference and overall health are also important. Always consult your GP for context.
How do I lose weight safely at 123 kg?
The NHS recommends losing 0.5–1 kg per week through a calorie deficit and increased physical activity. If you have weight-related health conditions, your GP can refer you to specialist services or discuss prescription options. Try our weight loss calculator to explore what's possible with structured support.
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.