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 13 Stone 8 Pounds in Kilograms?
13 stone 8 pounds (13st 8lb) equals 86.6 kilograms (kg) using the standard UK-to-metric weight conversion. This is a straightforward conversion: multiply the stone by 6.35029 and the pounds by 0.453592, then add them together. Understanding your weight in both imperial and metric units is helpful for NHS health appointments, fitness tracking, and using health calculators. Use our free weight converter above to switch between kg, stone, and lbs instantly whenever you need to.
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.
Converting 13st 8lb to Kilograms — The Calculation
To convert 13st 8lb to kg, use this simple formula: multiply the stone by 6.35029, then add the pounds multiplied by 0.453592.
- 13 stone × 6.35029 = 82.554 kg
- 8 pounds × 0.453592 = 3.629 kg
- Total: 86.183 kg (rounded to 86.6 kg)
This conversion is exact and used across NHS health systems and UK weight management services. Whether you're tracking your weight for health reasons, preparing for a GP appointment, or monitoring progress with a weight loss programme, having both metric and imperial measurements is useful. Our free weight converter tool on this page makes instant conversions effortless — just enter your weight in stone and pounds, and it automatically displays your weight in kilograms.
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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.
What Does 86.6kg Mean for Your Health?
At 86.6kg (13st 8lb), your health profile depends on your height and overall fitness. Use our free BMI calculator above to check your personal BMI — this gives you NHS-aligned health context. For example, if you're 5ft 8in (173cm) tall, a weight of 86.6kg gives you a BMI of approximately 30, which falls into the obese category according to NHS guidelines. However, BMI has limitations — it doesn't account for muscle mass or where fat is stored. If you're interested in weight management options, our GLP-1 weight loss calculator can help you understand potential weight loss projections based on different approaches. Your GP can provide personalised guidance about what your weight means for your individual health.
- 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 13st 8lb overweight according to NHS guidance?
Whether 13st 8lb (86.6kg) is overweight depends on your height. At average UK male height (5ft 9in), this BMI is approximately 28, which is overweight. At 5ft 6in (female average), BMI would be around 31, which is obese. Use our BMI calculator to check your personal BMI. Your GP can advise on your individual health risk.
How do I convert stone and pounds to kg quickly?
Multiply stone by 6.35, then add pounds multiplied by 0.454. For 13st 8lb: (13 × 6.35) + (8 × 0.454) = 82.55 + 3.63 = 86.2kg. Our free weight converter on this page does this instantly — just enter your weight in stone and it shows kg.
What's a healthy weight range for my height?
A healthy weight (BMI 18.5–24.9) depends on your height. At 5ft 8in, healthy weight is 55–74kg. At 5ft 5in, it's 52–70kg. Use our BMI calculator to calculate the healthy range for your exact height and see where you currently stand.
Can I lose weight from 13st 8lb safely?
The NHS recommends losing 0.5–1kg per week through a calorie deficit of 500 kcal/day. This involves diet and physical activity changes. If you're interested in prescription weight loss options, your GP can assess your eligibility and discuss approaches suited to your health.
Is Ozempic or Wegovy available for weight loss at this weight?
Wegovy (semaglutide) is the NHS-licensed weight management injection. Ozempic contains semaglutide but is licensed for diabetes only — not for weight loss. Eligibility for either requires a clinical assessment from your GP or a licensed prescriber, considering your BMI, health conditions, and individual circumstances.
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.