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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How to Manually Calculate Weight and BMI
If you prefer to work out weight conversions and BMI calculations by hand rather than using online tools, the formulas are straightforward and use simple maths. Whether you're converting between kilograms, stone, and pounds, or calculating your BMI for NHS health guidance, a UK pharmacy calculation takes just a few seconds once you know the conversion factors. This UK health guide walks you through each calculation step by step, with clear examples you can follow.
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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.
a UK pharmacy Weight Conversion Formulas
Kilograms to stone: Divide your weight in kg by 6.35029. For example, 70 kg ÷ 6.35029 = 11.03 stone (or 11 stone 0.4 lbs).
Kilograms to pounds: Multiply your weight in kg by 2.20462. So 70 kg × 2.20462 = 154.3 lbs.
Stone to pounds: Multiply stone by 14 (exactly). 11 stone × 14 = 154 pounds.
Stone and pounds to kg: This is more complex. Use: (stone × 6.35029) + (pounds × 0.453592). Example: (11 × 6.35029) + (4 × 0.453592) = 69.88 kg.
Alternatively, if you have a total in pounds, divide by 2.20462 to get kg. These conversion factors are the internationally accepted standard used by the NHS and UK health services.
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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.
a UK pharmacy BMI Calculation Formula
BMI (Body Mass Index) uses a simple formula: weight in kg ÷ height in metres squared. First, convert your height to metres (divide cm by 100). Then square it. Finally, divide your weight in kg by that number. Example: A person who is 173 cm tall (1.73 m) and weighs 70 kg: 70 ÷ (1.73 × 1.73) = 70 ÷ 2.99 = 23.4 BMI. According to NHS guidance, a BMI between 18.5 and 24.9 is a healthy weight range. Individual results vary, and BMI has limitations — it doesn't account for muscle mass. Use our free BMI calculator for gradual improvement, or our weight converter to switch between units before calculating manually.
- 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's the exact conversion from kilograms to stone?
One kilogram equals 0.157473 stone exactly. So divide your weight in kg by 6.35029 to get stone. For example, 80 kg ÷ 6.35029 = 12.6 stone. Conversely, 1 stone = 6.35029 kg. Always use these standard conversion factors for accurate UK weight measurements.
How do I convert stone and pounds to kilograms manually?
Multiply the stone figure by 6.35029, then multiply the pounds figure by 0.453592, then add them together. Example: 11 stone 7 pounds = (11 × 6.35029) + (7 × 0.453592) = 69.88 + 3.18 = 73.06 kg. This is the precise method used in NHS health guidance calculations.
Can I calculate my BMI if my height is in feet and inches?
Yes. Convert feet and inches to centimetres first (multiply feet by 30.48, then add inches × 2.54), then divide by 100 to get metres. Then use the standard BMI formula: weight in kg ÷ (height in metres squared). Alternatively, use our free BMI calculator which handles all conversions automatically.
What BMI range counts as healthy weight according to NHS guidance?
A BMI of 18.5 to 24.9 is considered healthy weight for most UK adults. However, for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower range of 18.5 to 22.9 because these groups have higher health risks at higher BMIs. Your GP can advise on what's healthy for you personally.
Why are the conversion factors 6.35029 and 2.20462 so specific?
These are the internationally standardised conversion factors between metric (kilogram) and imperial (stone/pounds) measurements. They come from the exact definitions: 1 pound = 0.453592 kg and 1 stone = exactly 14 pounds. Using these precise figures ensures consistency across NHS records, health guidance, and medical assessments across the UK.
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.