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
Body Fat Percentage Calculator — What You Need to Know
Body fat percentage measures the proportion of fat in your body compared to lean body mass (muscle, bone, organs). Unlike BMI, which only uses height and weight, body fat percentage gives a more accurate picture of your actual body composition and health risk. This guide explains healthy ranges, how body fat is calculated, and why it's a valuable complement to standard weight assessments. Use our free BMI calculator alongside body fat measures for a complete health overview.
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.
Body Fat Percentage Ranges and Categories
The healthy body fat percentage varies depending on your age and sex. Here are NHS and clinical guidelines:
- Women: Essential fat 10–13%, Athletic 14–20%, Fitness 21–24%, Acceptable 25–31%, Obese 32%+
- Men: Essential fat 2–5%, Athletic 6–13%, Fitness 14–17%, Acceptable 18–24%, Obese 25%+
Body fat percentage is more accurate than BMI because it distinguishes between muscle and fat. An athlete may have a high BMI but low body fat, while someone with a normal BMI might have excess fat hidden internally. Visceral fat (fat around organs) poses particular health risks even at moderate overall body fat levels. Your GP can refer you for professional body composition measurement using methods like DEXA scan, hydrostatic weighing, or bioelectrical impedance analysis if you need a precise reading.
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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.
Why Body Fat Matters More Than BMI Alone
While BMI is a useful screening tool, it cannot distinguish between muscle and fat. Two people with identical height and weight but different body fat percentages will have very different health profiles. Body fat vs BMI: BMI flags your weight category; body fat percentage reveals your actual composition. This is why athletes often have "overweight" BMI but excellent health markers. Additionally, where fat is stored matters — visceral fat around organs is more metabolically active and linked to type 2 diabetes and cardiovascular disease. Combining BMI assessment with body fat awareness gives a much clearer picture. Use our free weight converter to track changes in kg, stone, or lbs alongside body composition progress.
- 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 is body fat percentage calculated?
Body fat can be estimated using skinfold measurements (callipers), bioelectrical impedance scales, hydrostatic weighing, or DEXA scans. Online calculators use formulas based on age, sex, weight, and measurements, but clinical methods are more accurate. Your GP can refer you for professional assessment if needed.
Is a higher body fat percentage always unhealthy?
Not necessarily. Essential fat (10–13% for women, 2–5% for men) is vital for health. The "acceptable" range (25–31% for women, 18–24% for men) is healthy for most adults. Individual risk depends on age, fitness level, where fat is stored, and overall health markers like blood pressure and cholesterol.
Can you lose fat without losing weight?
Yes. If you build muscle through strength training while losing fat, your weight may stay similar but your body composition improves. This is why body fat percentage matters — the scale alone doesn't show this positive change. Track both metrics to see real progress.
How does body fat percentage relate to BMI?
BMI is a screening tool based only on height and weight. Body fat percentage shows actual composition. Someone with high BMI might have low body fat (muscle), while someone with normal BMI might have high body fat (poor composition). Using both gives a complete picture of health.
What's the difference between body fat and visceral fat?
Total body fat includes subcutaneous fat (under skin) and visceral fat (around organs). Visceral fat is metabolically active and linked to heart disease and diabetes risk, even at moderate total body fat levels. Reducing visceral fat through exercise and diet is particularly important for health.
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.