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 Find Your Body Fat Percentage
Body fat percentage measures the proportion of fat in your body compared to muscle, bone, and other tissues. Unlike BMI, which only uses height and weight, body fat percentage gives a clearer picture of your actual body composition and health. There are several methods to find your body fat percentage, ranging from simple calculations you can do at home to more accurate clinical measurements. Understanding your body fat percentage is especially useful alongside BMI for assessing your overall health and fitness.
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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.
Methods To Measure Body Fat Percentage
There are several ways to find your body fat percentage, each with different accuracy levels:
Simple calculation method: The Katch-McArdle Formula uses your lean body mass to estimate body fat. You'll need your weight in kilograms and waist measurement in centimetres. While not as precise as clinical methods, it's free and quick to do at home.
Clinical methods: Dual-energy X-ray absorptiometry (DEXA) scans are highly accurate and measure bone density alongside body composition. Bioelectrical impedance analysis (BIA) uses a small electrical current to estimate fat versus muscle — common in gyms and clinics. Hydrostatic weighing is considered a gold standard but requires specialist equipment.
Skinfold calipers: A trained professional measures skin thickness at several body sites using calipers. Accuracy depends heavily on the technician's experience. In the UK, DEXA scans are increasingly available through private health clinics and some NHS services.
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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.
Healthy Body Fat Percentage Ranges
The NHS and fitness organisations provide different body fat percentage ranges depending on age and sex. For women, body fat ranges from 10–13% (essential fat), 14–20% (athletic), 21–24% (fitness), 25–31% (acceptable), and 32% and above (obese category). For men, the ranges are 2–5% (essential fat), 6–13% (athletic), 14–17% (fitness), 18–24% (acceptable), and 25% and above (obese).
These ranges vary by age — older adults naturally have slightly higher body fat percentages whilst maintaining health. Your GP can discuss what a healthy body fat percentage means for your individual circumstances. Remember that visceral fat (fat around organs) is more health-damaging than subcutaneous fat (fat under skin), so body fat percentage alone doesn't tell the complete story. Use our free BMI calculator alongside body fat assessment for the most complete picture of 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.
What's the difference between body fat percentage and BMI?
BMI uses only height and weight, so it can't distinguish between muscle and fat. Body fat percentage measures the actual proportion of fat tissue in your body. Someone muscular might have a high BMI but low body fat. For a complete assessment, check both measurements — use our free BMI calculator and consider body fat percentage as well.
Can I calculate body fat percentage at home?
Yes, you can use simple formulas like the Katch-McArdle method with just your weight and waist measurement. However, these are estimates. For accuracy, consider DEXA scanning or bioelectrical impedance testing available at private clinics and some NHS services. Your GP can advise on appropriate measurement methods.
Why does body fat percentage matter more than just weight?
Two people at the same weight can have very different body compositions. One might be mainly muscle, the other mainly fat. Body fat percentage reveals what's actually making up your weight, giving better insight into health risks like cardiovascular disease and diabetes than weight or BMI alone.
What's a healthy body fat percentage for women in the UK?
According to fitness standards, 25–31% is considered acceptable for women, 21–24% is fitness level, and 14–20% is athletic. Ranges vary by age and individual circumstances. Your GP can discuss what's healthy for you specifically — these are general guidelines, not personal medical targets.
Is visceral fat worse than subcutaneous fat?
Yes, visceral fat (around internal organs) is more harmful to health than subcutaneous fat (under skin). Body fat percentage measurements don't distinguish between these types, so waist circumference is also important. The NHS recommends measuring waist circumference alongside weight and BMI for a fuller health picture.
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.