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 BMI Does 8.9 Pounds Give You?
8.9 pounds equals approximately 4.04 kilograms. However, your BMI depends entirely on your height — the same weight gives very different BMI values depending on how tall you are. Below we show what BMI 8.9 pounds (4.04kg) would give at six common UK heights, along with the NHS category each falls into. Use our free BMI calculator above to find your exact BMI using your personal measurements, or use the weight converter to see 4.04kg in stone and pounds.
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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.
BMI at Different Heights for 8.9 Pounds (4.04kg)
At 5ft 0in (152cm): BMI = 27.5 (overweight)
At 5ft 4in (163cm): BMI = 24.0 (healthy weight)
At 5ft 6in (168cm): BMI = 21.9 (healthy weight)
At 5ft 8in (173cm): BMI = 20.2 (healthy weight)
At 5ft 10in (178cm): BMI = 18.6 (healthy weight)
At 6ft 0in (183cm): BMI = 17.2 (underweight)
These examples show why height matters so much when calculating BMI. To convert 8.9 pounds to other units using the metric to imperial weight conversion system, 4.04kg also equals approximately 0.64 stone. Your GP can advise on whether your weight and BMI are healthy for your individual circumstances.
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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 NHS BMI Categories
According to NHS guidelines, a healthy BMI range is 18.5 to 24.9 for most UK adults. A BMI below 18.5 is classified as underweight, 25.0 to 29.9 is overweight, and 30.0 and above is obese. However, BMI has important limitations — it does not account for muscle mass, bone density, or where fat is stored on your body. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds due to higher health risks at the same weight. Always speak to your GP for personalised health advice based on your weight, height, and medical history rather than relying on BMI alone.
- 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 8.9 pounds to kilograms exactly?
Multiply 8.9 pounds by 0.453592. This gives 4.04kg. You can use our free weight converter above to convert between pounds, kilograms, and stone instantly for any weight.
Is 8.9 pounds a healthy weight for an adult?
8.9 pounds (4.04kg) is very light for an adult and would indicate underweight status at any typical height. Most UK adults weigh considerably more. Use our BMI calculator to check your personal BMI using your actual weight and height for context.
Why does BMI depend on height?
BMI measures weight in relation to height squared, so the same weight produces different BMI values at different heights. Taller people naturally weigh more while remaining in a healthy BMI range than shorter people.
Can I use this weight converter for imperial to metric conversions?
Yes. To convert kilograms to stone, divide by 6.35. To convert stone to kg, multiply by 6.35. Our free weight converter on this page handles all metric to imperial weight conversions instantly.
What should I do if my BMI is outside the healthy range?
Speak to your GP. They can assess your individual health, discuss whether your weight poses any health risks, and suggest appropriate support such as diet advice, exercise programmes, or specialist services if needed.
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.