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
BMI Calculator — Your Free UK Health Tool
A BMI calculator is one of the most useful tools for understanding your weight and overall health status. BMI (body mass index) measures the relationship between your weight and height, giving you a quick indicator of whether you're in a healthy weight range according to NHS guidelines. Our free BMI calculator above lets you check your personal BMI instantly by entering your weight and height in either kilograms, stone, or pounds — whatever feels most natural to you. Whether you're monitoring your weight for general health or exploring weight management options, knowing your BMI is an important first step in understanding your health.
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 Use the BMI Calculator and What Your Result Means
Simply enter your weight and height into our free BMI calculator above, and it will instantly calculate your BMI and show you where you fall on the NHS health scale. The calculator works in metric (kg and cm) or imperial (stone and pounds) — whichever you prefer. Your result will show you one of five categories: underweight (below 18.5), healthy weight (18.5–24.9), overweight (25.0–29.9), obese Class I (30.0–34.9), or obese Class II and above (35.0+). These categories are based on NHS guidance for UK adults and help identify potential health risks. If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends using slightly lower thresholds — your GP can explain what this means for your individual health. Remember that BMI is a screening tool; it doesn't account for muscle mass or where fat is stored, so if you have concerns about your weight or health, speak to your GP.
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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.
Understanding Your BMI Result and Next Steps
Once you know your BMI, you can use this information to make informed decisions about your health. A healthy BMI is between 18.5 and 24.9 according to NHS guidance. If your result shows you're outside the healthy range, there are many evidence-based approaches to weight management — from lifestyle changes like diet and exercise to talking with your GP about structured support programmes. For adults over 25 BMI with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea, prescription weight management options may be available through NHS specialist services or private online consultations. You can also use our free weight converter to understand your weight in different units, and our GLP-1 weight loss calculator to explore potential outcomes if you're considering prescription weight management.
- 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 exactly is BMI and why does it matter?
BMI (body mass index) is a measure of body fat based on your weight and height. It's used by the NHS and health services worldwide to screen for weight-related health risks. Your BMI helps identify whether you're at increased risk of conditions like type 2 diabetes, heart disease, or high blood pressure. It's not a perfect measure — it doesn't distinguish between muscle and fat — but it's a useful starting point for understanding your health.
What BMI range is considered healthy in the UK?
According to NHS guidelines, a healthy BMI for UK adults is between 18.5 and 24.9. A BMI of 25.0–29.9 is classified as overweight, and 30.0 and above is classified as obese. If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends slightly lower thresholds (18.5–22.9 for healthy weight) because these groups face higher health risks at the same BMI levels.
Can I lose weight if my BMI shows I'm overweight or obese?
Yes, absolutely. Even a modest weight loss of 5–10% of your body weight can significantly improve your health. The NHS recommends losing weight at a rate of 0.5–1 kg per week for sustainable results. This typically requires a calorie deficit of around 500 kcal per day, achieved through diet and increased physical activity. Your GP can recommend suitable approaches or refer you to specialist weight management services.
Is BMI accurate for everyone?
BMI is a useful screening tool but has limitations. It doesn't distinguish between muscle and fat — so athletes or very muscular people may have a high BMI but low body fat. It's also less accurate for older people (who naturally lose muscle with age) and doesn't account for where fat is stored. Waist circumference is also important: men should aim for under 94cm, women under 80cm.
What should I do after I've calculated my BMI?
If your BMI is in the healthy range, maintain your current habits with regular exercise and balanced nutrition. If it's outside the healthy range, consider speaking with your GP about weight management support. You can explore NHS tier 1 and 2 services (community programmes and digital tools), or if eligible, tier 3 specialist services. Use our weight converter to track your weight in your preferred units and our progress tracker to log your journey.
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.