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
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How to Calculate Body Weight Percentage
Body weight percentage refers to how your weight compares to a healthy range for your height, or sometimes to your body composition (the ratio of fat to muscle). Understanding your body weight percentage helps you assess whether you're in a healthy weight range according to NHS guidance. It's different from BMI but works alongside it to give a fuller picture of your health. This guide explains the most common ways to calculate and interpret body weight percentage in a UK context.
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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.
Body Weight Percentage vs BMI: What's the Difference?
Body weight percentage can mean two different things depending on context. First, it can refer to body fat percentage — the proportion of your total weight that is fat tissue versus muscle, bone, and water. Second, it can mean how your current weight compares to a healthy weight range as a percentage. BMI (body mass index) is a simpler calculation that doesn't distinguish between fat and muscle, so it has limitations — athletes with high muscle mass may have a high BMI but low body fat. Using our free BMI calculator above gives you your BMI instantly, but for a more complete picture, combining BMI with waist circumference measurement (following NHS guidance) provides better health insight. Men should keep waist circumference below 94cm (37 inches); women below 80cm (31.5 inches). This combination gives you a more accurate health assessment than body weight percentage alone.
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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.
How to Calculate Your Body Weight Percentage
If you want to calculate body fat percentage, the most accurate methods are DEXA scan, hydrostatic weighing, or bioelectrical impedance analysis — available through private clinics or NHS specialist services. For a rough estimate, you can use body fat percentage charts based on age and gender, though accuracy varies significantly. Alternatively, calculate how your weight compares to the healthy weight range for your height using our weight converter and BMI calculator tools on this page. A simpler approach: find your healthy weight range (usually 18.5 to 24.9 BMI), then see where your current weight falls as a percentage of that range. Your GP can discuss which method is most relevant for your personal health goals and whether weight management support might be helpful.
- 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.
What is a healthy body weight percentage in the UK?
For adults, a healthy body fat percentage typically ranges from 18–24% for men and 25–31% for women. However, "healthy" varies by age, fitness level, and individual health. NHS guidance focuses more on BMI (18.5–24.9) and waist circumference. Your GP can advise on what's healthy for you personally.
How do I calculate body weight percentage without expensive equipment?
You can estimate body composition using online body fat percentage calculators (which use age, weight, height, and measurements), though accuracy is limited. More reliable methods require professional assessment like DEXA scans or bioelectrical impedance. For practical health purposes, use our free BMI calculator and weight converter above to assess your weight against NHS healthy ranges.
Why does body weight percentage matter more than just BMI?
Body weight percentage shows whether your weight is muscle (healthy) or fat (health risk), whereas BMI doesn't distinguish between them. Athletes can have high BMI but low body fat. Combining BMI with waist circumference and body composition gives a fuller health picture. Both matter — BMI is a quick screening tool; body composition is more detailed.
Can I use body weight percentage to track weight loss?
Yes, tracking body fat percentage can be motivating during weight loss because you may lose fat while gaining muscle (scale weight stays similar). However, it requires repeat measurements using the same method for accuracy. Simpler tracking methods: weekly weigh-ins, waist circumference, or how clothes fit. Our free progress tracker helps you log all these metrics together.
Is calculating body weight percentage recommended by the NHS?
The NHS prioritises BMI and waist circumference for initial health screening. Body fat percentage assessment is typically offered through specialist weight management services or private fitness professionals. If you're concerned about your weight or health, your GP can refer you to appropriate services or discuss weight management support options available to you.
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.