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 Is 18.9 kg in Stone?
18.9 kg is equal to 2 stone and 13.1 pounds. To convert kilograms to stone, you divide the kilogram value by 6.35029, which is the standard kilogram to stone conversion factor used in the UK. At this weight, BMI varies significantly depending on your height — a healthy weight range depends on your individual circumstances and medical history. Use our free weight converter above to check other values, or try our BMI calculator to see how this weight relates to your personal health profile.
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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.
18.9 kg to Stone Conversion Table
Here's a quick reference table showing 18.9 kg alongside nearby values, making it easy to convert related weights in stone and pounds:
- 16 kg = 2 stone 7.1 lbs
- 17 kg = 2 stone 10.2 lbs
- 18 kg = 2 stone 13.2 lbs
- 18.5 kg = 2 stone 13.7 lbs
- 18.9 kg = 2 stone 13.1 lbs
- 19 kg = 3 stone 0.2 lbs
- 19.5 kg = 3 stone 1.2 lbs
- 20 kg = 3 stone 2.3 lbs
- 21 kg = 3 stone 5.4 lbs
- 22 kg = 3 stone 8.6 lbs
The conversion formula is: kg ÷ 6.35029 = stone. For stone and pounds together, multiply the stone result by 14 to get the total pounds value.
Clinically BackedWeight Loss
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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.
BMI Context at 18.9 kg
At 18.9 kg, your BMI depends entirely on your height. This is a very low body weight, typically seen in young children or very short adults. For context: at 5ft 3in (160 cm), 18.9 kg gives a BMI of 6.7 — well below the healthy weight range. At any realistic adult height, 18.9 kg would be classified as significantly underweight by NHS guidelines. If you're an adult weighing 18.9 kg, speak with your GP, as this may indicate an underlying health condition requiring support. Our free BMI calculator helps you understand your personal BMI across different heights.
- 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 18.9 kg to stone manually?
Divide 18.9 by 6.35029. This equals 2.975 stone. To express this as stone and pounds, take the decimal (0.975) and multiply by 14, which gives 13.65 pounds. So 18.9 kg = 2 stone 13.1 lbs approximately. Our weight converter above does this instantly.
Is 18.9 kg a healthy weight for an adult?
No. 18.9 kg is significantly underweight for any adult. Healthy weight ranges begin around 46 kg for a very short adult (under 5ft). If you or someone you know weighs 18.9 kg, it's important to speak with a GP to rule out underlying health conditions or nutritional concerns.
What is the exact stone to kg conversion formula?
The formula is: kg ÷ 6.35029 = stone. Conversely, to convert stone to kg, multiply: stone × 6.35029 = kg. These are the standard UK conversion factors. Our free BMI calculator and weight converter use these exact values.
How does 18.9 kg compare to average UK adult weight?
The average UK adult man weighs approximately 85.7 kg and the average woman weighs approximately 71.6 kg. At 18.9 kg, this is roughly 78% lighter than the average man and 74% lighter than the average woman — well outside normal adult weight ranges.
Can I use this conversion for children's weight?
Yes, the conversion formula works for any weight value. However, BMI categories for children are different — they use age and sex-specific growth charts. For children's health assessments, consult the NHS Healthy Weight Calculator for children, not adult BMI ranges.
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.