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 My Body Fat Percentage?
Your body fat percentage is the proportion of your total body weight that is fat, expressed as a percentage. Unlike BMI, which only considers height and weight, body fat percentage measures your actual body composition — distinguishing between fat mass and lean body mass (muscle, bone, organs). Understanding your body composition gives you a more complete picture of your health than weight alone. Use our free body composition calculator above to estimate your body fat percentage, then explore what the results mean for your fitness and 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 Percentage Results
Body fat percentage ranges vary significantly by age and gender. For women, a healthy body fat range is typically 21–24%, with athletic levels at 14–20% and essential fat (vital for organ function) at 10–13%. For men, a fitness range is 14–17%, athletic is 6–13%, and essential fat is 2–5%. Generally, body fat percentages above 32% for women and 25% for men are considered obese, though these are screening ranges only — your GP can give personalised advice based on your individual health. The calculator on this page estimates your body fat percentage using standard formulas, but remember that actual measurement (via DEXA scan or hydrostatic weighing) is more precise. Age matters too: as we grow older, body fat naturally increases even if weight stays the same, due to muscle loss. Our free BMI calculator can complement this data by showing where your overall weight sits relative to your height.
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 — Which Matters More?
BMI and body fat percentage measure different things. BMI uses only height and weight, making it quick and accessible — ideal for population-level screening. However, BMI cannot distinguish between muscle and fat, so athletes may have a high BMI but low body fat. Body fat percentage directly measures fat mass, making it more specific for health risk assessment. Together, they provide a fuller picture: you might have a healthy BMI but elevated body fat (poor muscle tone), or a higher BMI with low body fat (muscular build). For visceral fat assessment — the more dangerous deep abdominal fat linked to heart disease and diabetes — waist circumference is also important. The NHS recommends using multiple metrics rather than relying on any single number. Use both the body composition calculator and our free BMI calculator on this page to see the complete context 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.
Is body fat percentage more accurate than BMI?
Both have value but measure different things. Body fat percentage directly measures fat mass, making it more specific for assessing body composition. BMI is a useful screening tool but cannot distinguish muscle from fat. For the most complete picture, use both metrics alongside waist circumference. Your GP can interpret both in the context of your individual health.
What body fat percentage should I aim for?
Healthy ranges vary by age and gender. For women, 21–24% is typical; for men, 18–24%. However, "ideal" depends on your fitness goals, age, and health status — not appearance alone. Very low body fat (<13% for women, <6% for men) is difficult to maintain and may not be necessary for health. Speak to your GP or a registered dietitian about realistic targets for you.
How is body fat percentage calculated?
Our calculator uses prediction formulas based on height, weight, age, and gender — standard methods used in public health. These formulas are reasonably accurate for screening but less precise than clinical methods like DEXA scans or hydrostatic weighing. Clinical measurements are typically only available privately or through research studies, not routinely on the NHS.
Does body fat percentage change with age?
Yes, significantly. Body fat naturally increases with age, even if weight stays constant, because we lose muscle mass over time. A 50-year-old with the same weight as a 25-year-old will typically have higher body fat percentage due to reduced muscle. Regular strength exercise can help slow this age-related muscle loss.
Can I have a healthy BMI but high body fat percentage?
Yes — this is sometimes called "normal weight obesity." You might fall in a healthy BMI range but still carry excess fat mass, particularly if you do little strength training. Conversely, very muscular individuals may have a higher BMI but low body fat. This is why using both metrics together, plus your weight converter and BMI calculator, gives better insight than either alone.
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.