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's 13 Stone 13 Pounds in Kilograms and BMI?
13 stone 13 pounds converts to approximately 88.5 kg. However, your BMI depends on your height, not just your weight. Use our free BMI calculator above to find your personal BMI instantly, or see the examples below for different heights. This helps you understand where you fall on the NHS BMI scale and what it means for your health.
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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.
BMI at 13 Stone 13 Pounds (88.5 kg) — Height Examples
BMI is calculated using weight and height together. At 88.5 kg, here's what your BMI would be at common UK heights:
- 5ft 4in (163cm): BMI = 33.1 — Obese (Class I)
- 5ft 6in (168cm): BMI = 30.4 — Obese (Class I)
- 5ft 8in (173cm): BMI = 28.6 — Overweight
- 5ft 10in (178cm): BMI = 26.9 — Overweight
- 6ft 0in (183cm): BMI = 25.1 — Healthy weight
- 6ft 2in (188cm): BMI = 23.5 — Healthy weight
Your height makes a significant difference. The taller you are, the lower your BMI at this weight. Use the weight converter and BMI calculator on this page to check your exact figures.
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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.
NHS BMI Categories and What They Mean
According to NHS guidelines, a healthy BMI for UK adults is between 18.5 and 24.9. At 88.5 kg, whether you fall into overweight or obese depends entirely on your height. BMI is useful as a screening tool, but it has limitations — it doesn't account for muscle mass, where fat is stored, or individual fitness levels. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends slightly lower BMI thresholds due to higher health risks at lower weights. Your GP can discuss what your weight means for your individual health and whether any action is needed.
- 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 13 stone 13 pounds to kilograms exactly?
Multiply stone by 6.35029 and pounds by 0.453592, then add together. 13 stone 13 pounds = (13 × 6.35029) + (13 × 0.453592) = 82.554 + 5.897 = 88.45 kg, or approximately 88.5 kg. Use our free weight converter above for instant conversions between kg, stone, and pounds.
Is a BMI of 28 healthy according to NHS guidelines?
No. The NHS defines healthy BMI as 18.5 to 24.9. A BMI of 28 falls in the overweight category (25.0–29.9). However, BMI is just one health indicator. Your waist circumference, fitness level, and overall health also matter. Your GP can assess your personal health risk.
Does 88.5 kg mean I need to lose weight?
That depends on your height, age, fitness, and overall health. At 88.5 kg, a person at 5ft 4in may have health concerns, while someone at 6ft 2in may be perfectly healthy. Use our BMI calculator to find your personal BMI, then discuss the results with your GP for personalised advice.
Can I use BMI to track weight loss progress?
BMI is useful for tracking general trends, but progress trackers that measure both weight and height changes give better insight. Our free progress tracker lets you log weight loss and see how your BMI improves over time as you lose weight.
What if I'm muscular — does BMI still apply to me?
BMI has limitations for very muscular individuals because muscle weighs more than fat. BMI alone doesn't distinguish between muscle and fat. If you're athletic or strength-train regularly, discuss your weight and body composition with your GP rather than relying solely on BMI.
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.