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 a Normal Body Fat Index?
Your body fat percentage is a key measure of body composition — showing the proportion of your weight that is fat versus muscle and bone. Unlike BMI, which can't distinguish between muscle and fat, body fat percentage gives a clearer picture of your actual body composition. A normal body fat index varies by gender and age, and understanding where you fall can help you assess your health more accurately than BMI alone. Use our free body fat calculator on this page to find your healthy range instantly.
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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.
How to Interpret Your Body Fat Calculator Results
Our body fat calculator provides results in percentages, along with a category that shows where you fall on the healthy body fat spectrum. For women, a healthy body fat range is typically 21–31%, with athletic individuals at 14–20%. For men, healthy ranges sit at 18–24%, with athletic individuals at 6–13%. These reference ranges are based on the American Council on Exercise (ACE) standards, widely used in UK fitness and health assessments.
- Essential fat — the minimum fat needed for organ protection and bodily functions (10–13% for women, 2–5% for men)
- Athletic — very lean, typically seen in competitive athletes and fitness professionals
- Fitness — lean and healthy, achievable with regular exercise and balanced nutrition
- Acceptable — within normal healthy range for most adults
- Obese — elevated health risks, typically 32%+ for women and 25%+ for men
Remember that individual results vary based on age, genetics, and muscle-building activity. Your GP can provide personalised guidance on what your body fat percentage means for your specific health situation.
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.
Body Fat Percentage vs BMI — When Each Matters
Body fat percentage and BMI measure different things, so they're useful in different contexts. BMI uses height and weight to estimate whether you're in a healthy range — it's quick, free, and effective for population screening. However, BMI doesn't distinguish between muscle and fat, so athletes may show an "overweight" BMI despite being very lean. Body fat percentage is more precise for understanding actual body composition, but requires measurement (skinfold calipers, bioelectrical impedance, or professional assessment). Use our free BMI calculator on this page to check both metrics together for a complete health picture. Visceral fat — fat stored around your organs — is also important to monitor; waist circumference is a simple proxy for this, measured at the level of your navel.
- 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's the difference between body fat percentage and BMI?
BMI measures height versus weight to estimate if you're in a healthy range, but doesn't distinguish muscle from fat. Body fat percentage shows the actual proportion of fat in your body, making it more precise for body composition assessment. Athletes may have high BMI but low body fat. Both metrics together give a fuller health picture.
What body fat percentage should I aim for?
Healthy ranges vary by gender and age. Women typically aim for 21–31%, men 18–24%. Athletes may target lower ranges (14–20% for women, 6–13% for men). Your GP can advise what's appropriate for your individual health goals and circumstances.
How is body fat percentage measured accurately?
Common methods include skinfold calipers, bioelectrical impedance devices, DEXA scans, and hydrostatic weighing. Home scales with bioelectrical impedance are convenient but less precise. For accurate assessment, visit a health professional or fitness centre with calibrated equipment.
Can I have a high body fat percentage with a healthy BMI?
Yes — this is called "normal weight obesity." Someone can have a healthy BMI (18.5–24.9) but elevated body fat percentage, especially if they have low muscle mass. This is why body composition matters alongside BMI for a complete health assessment.
Does body fat percentage change with age?
Yes, body fat typically increases with age as muscle mass naturally declines. Recommended ranges may shift slightly over time. Regular exercise and adequate protein help maintain muscle mass and support healthier body composition as you age.
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.