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 51kg in Stones and Pounds?
51 kilograms converts to 8 stone and 0.3 pounds using the standard metric to imperial weight conversion. In UK measurements, this weight is commonly expressed as 8 stone, which is how most British adults describe their body weight. Your BMI at this weight depends entirely on your height — the same weight can fall into different NHS health categories depending on how tall you are. Use our free BMI calculator above to find your personal BMI, or check the examples below for common UK heights.
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.
What Is Your BMI at 51kg?
BMI (body mass index) measures weight in relation to height. At 51kg, your BMI varies significantly depending on your height. Here are typical examples:
- At 150cm (4ft 11in): BMI = 22.7 (healthy weight, NHS category)
- At 160cm (5ft 3in): BMI = 19.9 (healthy weight)
- At 165cm (5ft 5in): BMI = 18.7 (healthy weight)
- At 170cm (5ft 7in): BMI = 17.6 (healthy weight)
- At 175cm (5ft 9in): BMI = 16.7 (underweight threshold)
- At 180cm (5ft 11in): BMI = 15.7 (underweight)
At 51kg, most adults fall within the healthy weight range. Your exact BMI tells you whether this weight is appropriate for your individual height. Calculate your personal BMI now using the calculator on this page.
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.
NHS BMI Categories and What They Mean
According to NHS guidelines, a healthy BMI is between 18.5 and 24.9 for most UK adults. BMI categories are: underweight (below 18.5), healthy weight (18.5–24.9), overweight (25.0–29.9), and obese (30.0+). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — healthy weight starts at 18.5 but obese begins at 27.5 rather than 30.0. BMI is a useful screening tool but has important limitations: it does not distinguish between muscle and fat, and does not account for where fat is stored. Your GP can give you personalised advice about what your BMI means for your 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.
How do I convert 51kg to stone?
Divide 51kg by 6.35029 (the conversion factor) to get 8.04 stone, which rounds to 8 stone. To express the decimal as pounds, multiply 0.04 by 14 to get approximately 0.3 pounds. So 51kg = 8 stone 0.3lbs.
Is 51kg a healthy weight?
Whether 51kg is healthy depends on your height and body composition. At 51kg, most adults fall within the healthy BMI range (18.5–24.9) according to NHS guidelines. Use the weight converter and BMI calculator on this page to check your personal BMI at your actual height.
What does underweight mean on the BMI scale?
A BMI below 18.5 is classified as underweight by NHS standards. At 51kg, taller adults (above 5ft 8in or 173cm) may fall into this category. Being underweight can affect bone density and immune function. Discuss with your GP if your BMI is consistently below 18.5.
Can I convert stone to kg using a simple formula?
Yes — multiply stone by 6.35029 to convert to kilograms. For example, 8 stone × 6.35029 = 50.8kg. This is the standard metric to imperial conversion used on NHS health charts and UK weight converters.
Why does BMI vary by height?
BMI measures how weight is distributed across height. Taller people carry the same weight over a greater frame, so BMI is lower. Shorter people have the same weight compressed into less height, giving a higher BMI. This is why BMI must always be calculated individually for each height.
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.