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 Calculator — Understanding Your Results
Body fat percentage is a key measure of your overall health and body composition, showing what proportion of your weight is fat versus lean tissue like muscle and bone. Unlike BMI, which only considers height and weight, body fat gives a more complete picture of your fitness level and health status. Our free body fat calculator helps you assess where you stand and what your results mean for your wellbeing.
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.
How to Interpret Your Body Fat Calculator Results
Your body fat percentage falls into specific categories based on gender, and understanding where you fall helps you set realistic health goals. For women, essential fat ranges from 10–13%, athletic body fat is 14–20%, fitness level is 21–24%, acceptable range is 25–31%, and anything above 32% is classified as obese. For men, the ranges are slightly lower: essential fat is 2–5%, athletic is 6–13%, fitness is 14–17%, acceptable is 18–24%, and obese is 25% or above.
These healthy body fat ranges reflect the biological differences between men and women. Women naturally carry more essential fat due to hormonal and reproductive needs. Your calculator result shows which category you fall into, helping you understand your current body composition status. Remember that body fat percentage varies with age, genetics, fitness level, and individual factors — these are general guidelines, not absolutes.
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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 — Which Matters More?
BMI and body fat percentage measure different things and both have value. BMI is a quick screening tool using only height and weight — it cannot distinguish between muscle and fat. A muscular athlete might have a "high" BMI but low body fat. Body fat percentage directly measures your actual fat mass, making it more specific for assessing body composition and visceral fat risk.
For most people, checking both metrics gives the clearest picture. Use our free BMI calculator alongside your body fat results to get a fuller understanding of your health status. Body fat percentage is particularly useful if you're strength training, as it shows progress even if your weight stays the same. Your GP can advise which metric is most relevant to your individual health goals.
- 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 fat percentage for adults in the UK?
Healthy ranges vary by gender. For women, 25–31% is considered acceptable; for men, 18–24%. Athletic individuals typically have lower percentages (women 14–20%, men 6–13%). These are guidelines — age, genetics, and fitness level also affect what's healthy for you personally.
How does body fat percentage differ from BMI?
BMI only uses height and weight, so it cannot distinguish muscle from fat. Two people with the same BMI can have very different body compositions. Body fat percentage directly measures your actual fat mass, making it more specific for understanding your true body composition and health status.
Can body fat calculators be inaccurate?
Many body fat calculators use estimation methods (measurements or bioelectrical impedance) that have a margin of error of ±3–5%. For the most accurate measurement, DEXA scans or underwater weighing are gold standard but less accessible. Home calculators are useful for tracking trends over time.
What causes changes in body fat percentage?
Diet, exercise, age, hormones, and genetics all affect body fat. Strength training builds muscle which can lower body fat percentage even without major weight loss. A calorie deficit supports fat loss, while adequate protein intake helps preserve muscle during weight loss.
Should I focus on body fat percentage or weight loss?
Both metrics matter. Weight loss alone doesn't assures fat loss — you want to lose fat while preserving muscle. Tracking body fat percentage alongside weight gives you a clearer picture of whether your lifestyle changes are working effectively for your 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.