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
Calculate Your Body Fat Percentage
Body fat percentage is a more precise measure of health than weight alone, showing what proportion of your body is actually fat versus muscle and bone. Unlike your overall weight or BMI, body fat percentage reveals your true body composition — which is why two people at the same weight can look completely different. Use our free body fat calculator above to find your body fat percentage, and discover how it compares to healthy ranges for your age and gender.
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 Results
Your body fat calculator result falls into one of five categories based on your gender and age. For women, essential body fat ranges from 10–13%, athletic from 14–20%, fitness from 21–24%, acceptable from 25–31%, and obese from 32% and above. For men, the ranges are lower: essential fat 2–5%, athletic 6–13%, fitness 14–17%, acceptable 18–24%, and obese from 25% upwards.
These reference ranges account for the fact that women naturally carry more essential fat for reproductive health. A result in the "fitness" or "athletic" category doesn't necessarily mean you're unhealthy if you're in the "acceptable" range — it depends on your individual goals and overall health. If your result concerns you, speak to your GP about what healthy body fat looks like for you specifically.
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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.
Body Fat Percentage vs BMI — Which Matters More?
Your BMI and body fat percentage measure different things. BMI uses height and weight to estimate whether you're in a healthy weight range, but it cannot distinguish between muscle and fat. A muscular athlete might have a high BMI but low body fat. Body fat percentage, by contrast, directly measures the proportion of fat in your body — making it a more accurate picture of your actual body composition.
For most people, checking both metrics gives the clearest health picture. Use our free BMI calculator alongside this body fat tool to see how your measurements align. If there's a significant gap between your BMI category and your body fat percentage, your GP can help you understand what this means for your health and whether lifestyle changes are needed.
- 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.
Is body fat percentage more accurate than BMI?
Both are useful but measure different things. Body fat percentage directly shows how much fat you carry, while BMI estimates health risk from weight and height alone. Body fat percentage is more accurate for muscular individuals, but BMI is simpler to calculate and track over time. Using both together gives the clearest picture of your body composition.
What is a healthy body fat percentage for a woman?
For women, a healthy body fat range is typically 20–32% depending on age and fitness level. The fitness category (21–24%) is ideal for active women, whilst the acceptable range (25–31%) is still considered healthy for most adults. Individual targets vary — ask your GP if you're unsure what's right for you.
What is a healthy body fat percentage for a man?
For men, healthy body fat usually ranges from 10–20%, with athletic levels at 6–13% and fitness levels at 14–17%. Most healthy adult men fall in the acceptable range of 18–24%. Anything above 25% may increase health risks, though individual factors like age and fitness level matter.
Can I lose body fat without losing weight?
Yes — if you're building muscle whilst losing fat, your weight might stay the same or even increase, but your body fat percentage will drop. This is why body composition matters more than the number on the scales. Track your body fat percentage alongside your weight for a complete picture of progress.
How often should I measure my body fat?
Measure every 4–6 weeks to see meaningful changes. More frequent measurements can be frustrating because body fat shifts slowly and fluctuates with hydration, hormones, and meal timing. Aim for consistency — measure at the same time of day, in similar conditions, to get accurate comparisons over time.
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.