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
12.9 Stone in Pounds — What's Your BMI?
12.9 stone is equivalent to 180.5 pounds, but your BMI depends entirely on your height. This weight falls into different NHS categories depending on how tall you are. For example, someone 5ft 6in (168cm) with this weight would have a BMI of 29.2 (overweight), whilst someone 6ft tall (183cm) would have a BMI of 24.5 (healthy weight). Use our free BMI calculator above to find your exact BMI instantly by entering your height alongside this weight.
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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.
12.9 Stone BMI at Different Heights
12.9 stone (180.5 lbs or 82 kg) produces different BMI values across common UK heights:
- 5ft 2in (157cm): BMI 30.7 — Obese (Class I)
- 5ft 6in (168cm): BMI 29.2 — Overweight
- 5ft 10in (178cm): BMI 25.9 — Overweight
- 6ft (183cm): BMI 24.5 — Healthy weight
- 6ft 2in (188cm): BMI 23.3 — Healthy weight
To convert this weight accurately to your personal BMI, our free BMI calculator uses your exact height to give you a precise result. BMI calculation uses the formula: weight (kg) ÷ height (m)². These NHS categories apply to most UK adults, though ethnicity-adjusted thresholds are lower for South Asian, Chinese, Black African, and Black Caribbean adults.
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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.
Understanding Your BMI Category
The NHS divides BMI into five main categories for adults. A BMI under 18.5 is underweight, 18.5–24.9 is a healthy weight, 25–29.9 is overweight, and 30–39.9 is obese. At 12.9 stone, your category depends on your height. However, BMI has important limitations — it doesn't distinguish between muscle and fat, so athletes may have a high BMI but low body fat. Waist measurement also matters: men over 102cm (40in) or women over 88cm (34.5in) face increased health risks regardless of BMI. For personalised advice on what your weight means for your health, speak to your GP.
- 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 12.9 stone in pounds exactly?
12.9 stone equals 180.5 pounds exactly. One stone = 14 pounds, so 12.9 × 14 = 180.5 lbs. To convert to kilograms (used by the NHS), 12.9 stone = 82 kg. Use our weight converter above to switch between kg, stone, and pounds instantly.
Is 12.9 stone a healthy weight?
Whether 12.9 stone is healthy depends entirely on your height. At 5ft 6in it's overweight (BMI 29.2), but at 6ft it's healthy (BMI 24.5). Use our BMI calculator above with your actual height to find out whether this weight falls in the healthy range for you personally.
What's the healthy weight range for my height if I weigh 12.9 stone?
If you're 5ft 6in, the healthy range is roughly 8st 9lbs to 11st 6lbs. At 5ft 10in, it's 9st 5lbs to 12st 7lbs. At 6ft, it's 10st 2lbs to 13st 8lbs. These are NHS-based ranges. Enter your height in our free BMI calculator to see your personal healthy weight range.
How do I know if my BMI is healthy?
According to NHS guidelines, a healthy BMI is 18.5–24.9. However, BMI doesn't account for muscle mass, where fat is stored, or your ethnicity. Lower BMI thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults. Your GP can give you personalised advice based on your overall health, not just BMI.
Should I aim to lose weight at 12.9 stone?
This depends on your height, age, health conditions, and medical history — not just the number on the scales. If your BMI is in the healthy range, weight loss may not be necessary. If your BMI is overweight or obese, losing 5–10% of your body weight can have real health benefits. Speak to your GP for personalised advice on whether weight loss is appropriate for you.
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.