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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Body Mass Calculation Chart — Understanding Your Results
A body mass calculation chart helps you understand whether your weight falls within a healthy range for your height and age. Unlike BMI alone, which doesn't distinguish between muscle and fat, body composition analysis looks at your overall body mass distribution. This guide explains how to interpret calculator results, what healthy ranges mean for your gender, and how body composition fits into your broader health picture alongside other measurements like BMI and waist circumference.
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 Mass Calculator Results
The body mass calculation chart on this page uses your height, weight, age, and gender to estimate your body composition and total body mass. Results are presented across several key metrics:
- Total body mass: Your overall weight in kg or stone and pounds
- Body fat percentage: The proportion of your total weight that is fat tissue — ranges vary significantly by gender and age
- Lean body mass: The weight of everything that isn't fat, including muscle, bone, organs, and water
- Healthy body fat range: The target percentage for your age and gender according to fitness and health guidelines
Reference ranges differ for men and women because women naturally have higher body fat percentages. For example, a healthy body fat percentage for women aged 25–35 is typically 18–25%, while for men the same age it's 10–17%. Use our free BMI calculator alongside this tool to get a complete picture of your health metrics.
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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 — When to Use Each
Body composition and BMI measure different things. BMI shows weight relative to height only — it can't tell if that weight is muscle or fat. Body fat percentage reveals the actual composition of your body mass. An athlete might have a high BMI but low body fat, while someone sedentary might have a normal BMI but excess body fat concentrated around the organs (visceral fat), which carries greater health risks.
For a complete health picture, use both metrics: track your BMI using our free BMI calculator for screening purposes, and monitor body fat percentage to understand your actual tissue composition. Your GP may also recommend checking waist circumference, as this measures central fat distribution — an important predictor of cardiovascular and metabolic health independent of overall weight.
- 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 a healthy body fat percentage for UK adults?
Healthy ranges vary by age and gender. For women, 18–25% is typical for ages 25–35, increasing slightly with age. For men, 10–17% is healthy in the same age range. These ranges are based on fitness standards and health guidelines. Your individual target depends on your age, fitness level, and health goals — your GP can advise what's appropriate for you.
Why is body fat percentage more useful than BMI alone?
BMI doesn't distinguish muscle from fat — a muscular person might have a high BMI but low body fat. Body fat percentage shows actual tissue composition. However, both are useful: BMI is a quick screening tool, while body fat percentage gives a more detailed picture. Use the BMI calculator and body composition assessment together for best results.
Can I reduce body fat percentage without losing weight?
Yes, through strength training. If you build muscle while losing fat, your total weight may stay the same but your body fat percentage drops. This is why the scale alone isn't the best measure of progress — body composition matters more. Track both weight and body fat percentage for a complete view.
How does age affect healthy body fat ranges?
Body fat naturally increases with age due to muscle loss and metabolic changes. A healthy body fat percentage for a 25-year-old woman (20%) is lower than for a 45-year-old woman (26%). Age-adjusted ranges account for this. Use the body mass calculation chart with your age selected to see the target range for you.
Is visceral fat more dangerous than subcutaneous fat?
Yes. Visceral fat (stored around organs) is more metabolically active and linked to type 2 diabetes and cardiovascular disease, even in people with normal BMI. Subcutaneous fat (under skin) is less harmful. Waist circumference is a better predictor of visceral fat than overall body fat percentage — your GP can advise safe limits.
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.