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 Does 18 Stones Mean for Your Health in the UK?
18 stones is equivalent to approximately 114.3 kilograms or 252.3 pounds. In UK health context, this weight falls into the obese category according to NHS guidelines for most adults. Understanding where your weight sits on the health spectrum is an important first step towards managing your wellbeing. Your GP can provide personalised advice about what this weight means for your individual health profile, taking into account your height, age, and any existing health conditions.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
NHS Weight Categories and What 18 Stones Means
According to NHS guidance, weight categories are determined by BMI (body mass index), which uses both weight and height. At 18 stones, your BMI depends on your height — for example, an adult of average height (5ft 7in) would have a BMI of approximately 36, placing them in the obese category. The NHS defines obesity as a BMI of 30 and above, with further classifications for Class I (30–34.9), Class II (35–39.9), and Class III or severe obesity (40 and above).
It's important to note that BMI has limitations — it does not distinguish between muscle and fat, so muscular individuals may have a high BMI but low body fat. Additionally, for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, NHS guidance recommends lower BMI thresholds due to higher health risks at the same BMI levels.
Use our free BMI calculator above to determine your exact BMI based on your height and current weight, then discuss the results with your GP.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Weight Management and UK Health Resources
If you're at 18 stones and looking to manage your weight, the NHS offers several evidence-based pathways. Your GP can refer you to a tier 2 or tier 3 weight management service, which may include behaviour change programmes, dietary support, and potentially prescription medications if you meet eligibility criteria. For adults with a BMI over 30 and weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea, treatment options may include lifestyle interventions or GLP-1 receptor agonist medications like Mounjaro or Wegovy — though these require prescription and individual clinical assessment.
Sustainable weight loss typically occurs at a rate of 0.5–1 kg per week. Use our weight converter to track your progress in both metric and imperial units, and log your journey with our free progress tracker.
- 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.
Is 18 stones overweight or obese?
Whether 18 stones falls into the overweight or obese category depends on your height. For most adults, 18 stones places you in the obese range (BMI 30+). Use our BMI calculator to check your personal BMI, then speak with your GP about what this means for your health.
How many kilograms is 18 stones?
18 stones equals approximately 114.3 kg. The exact conversion is 18 × 6.35029 = 114.3 kg. You can use our weight converter to switch between stone, kilograms, and pounds instantly.
What's a healthy weight for my height?
Healthy weight depends on your height. The NHS BMI range for healthy weight is 18.5 to 24.9. Our BMI calculator above can show you the healthy weight range for your specific height — use it to get a personalised target.
What weight loss support is available on the NHS?
Your GP can refer you to weight management services, which may offer behaviour change programmes, dietician support, or prescription medications if you meet eligibility criteria. Access varies by region, so discuss options with your practice.
Can prescription weight loss injections help at 18 stones?
Adults with a BMI over 30 may be eligible for prescription GLP-1 medications like Mounjaro or Wegovy, subject to clinical assessment and certain health criteria. However, these are always used alongside dietary changes and increased physical activity, not as a standalone treatment.
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.