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 Health Calculator — What Your Results Mean
Your BMI (Body Mass Index) is a simple health screening tool that helps you understand whether your weight is in a healthy range for your height. Our free BMI health calculator on this page calculates your result instantly using your weight and height. Understanding your BMI and where you fall within the NHS bmi categories uk can help you make informed decisions about your health, whether that's maintaining your current weight or making lifestyle changes. This guide explains the BMI formula, what your results mean, and how to use them alongside other health measures.
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.
BMI Formula and NHS Healthy Weight Ranges
The BMI formula is straightforward: divide your weight in kilograms by your height in metres squared. Using our BMI health calculator above, you don't need to do the maths yourself — just enter your weight and height, and your result appears instantly.
The NHS defines these bmi categories uk:
- Under 18.5: Underweight
- 18.5–24.9: Healthy weight (this is the healthy bmi range)
- 25.0–29.9: Overweight — the overweight bmi threshold starts at 25
- 30.0–34.9: Obese (Class I)
- 35.0–39.9: Obese (Class II)
- 40.0+: Severely obese (Class III)
If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — a healthy BMI range of 18.5–22.9 and overweight starting at 23.0, because these groups face higher health risks at lower BMI levels.
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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 BMI Limitations and Taking Action
While BMI is a useful screening tool, it has important bmi limitations — it doesn't distinguish between muscle and fat, so athletes may have a high BMI despite being very fit. BMI also doesn't account for where fat is stored; waist circumference matters too. For this reason, your GP may assess other factors like blood pressure, cholesterol, and waist measurement alongside your BMI.
If your BMI falls outside the healthy range, even a 5–10% reduction in your current weight can bring meaningful health improvements. Use our free weight converter above to check equivalent weights in stone and kilograms, and speak to your GP about realistic, sustainable targets for your individual health situation.
- 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 normal BMI for UK adults?
According to NHS guidelines, a healthy BMI is between 18.5 and 24.9 for most UK adults. Use our free BMI calculator above to find your personal result. For people of South Asian, Chinese, Black African, or Black Caribbean backgrounds, the NHS recommends a lower healthy range of 18.5–22.9 because these groups have higher health risks at standard BMI levels.
Is BMI accurate for everyone?
BMI is a useful screening tool but has limitations. It doesn't account for muscle mass, so athletes may have a higher BMI despite being fit. It also doesn't show where body fat is stored. Your GP may use additional measures like waist circumference and blood tests to give you a fuller picture of your health.
What should I do if my BMI is outside the healthy range?
Speak to your GP first — they can assess your individual health needs. Even a 5–10% weight reduction can improve health outcomes. Your GP may suggest lifestyle changes, referral to weight management services, or other support depending on your circumstances.
Does BMI work the same way for children?
No — children's BMI uses age and sex-specific centile charts, not adult categories. If you're concerned about a child's weight, speak to your GP or health visitor. The NHS Healthy Weight Calculator has a section specifically for children.
How does BMI relate to overall health?
BMI is one screening measure alongside other factors like blood pressure, cholesterol, waist circumference, and physical fitness. A healthy BMI is associated with lower risk of type 2 diabetes, heart disease, and certain cancers. Your GP can explain what your BMI means for your specific health profile.
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.