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
Find Your BMI — How to Calculate and Understand Your Result
Finding your BMI is the first step to understanding your weight in relation to your height. BMI (body mass index) is a simple screening tool used by the NHS to assess whether an adult's weight falls within a healthy range. In just a few seconds, you can calculate your personal BMI and see where you stand on the official UK health scale. Whether you're curious about your health, preparing for a GP appointment, or tracking your wellness journey, knowing your BMI gives you a clear baseline for discussion with healthcare professionals.
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 Calculate Your BMI and Find Your Range
The BMI formula is straightforward: divide your weight in kilograms by your height in metres squared (weight ÷ height²). For example, someone weighing 70kg and 1.73m tall would have a BMI of 23.4. Once you have your number, check it against the NHS BMI categories: under 18.5 is underweight, 18.5–24.9 is healthy weight, 25–29.9 is overweight, 30–34.9 is obese (Class I), 35–39.9 is obese (Class II), and 40+ is severely obese. Use our free BMI calculator above to find your exact BMI instantly — just enter your weight in kg or stone, and your height in cm or feet and inches.
- Healthy BMI range: 18.5–24.9 according to NHS guidelines
- For South Asian, Black African, or Chinese adults: Lower thresholds apply — discuss with your GP for personalised guidance
- Your healthy weight range: Use the BMI calculator to see the target weight band for your specific 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.
BMI Limitations and What Else Matters
BMI has important limitations — it doesn't distinguish between muscle and fat, so athletes or very muscular individuals may have a higher BMI despite low body fat. It also doesn't account for age, bone density, or where fat is stored on your body. The NHS recommends using BMI alongside waist circumference for a fuller picture: men should aim for under 94cm (37 inches), women under 80cm (31.5 inches). If your BMI falls outside the healthy range, your GP can discuss your individual circumstances, family history, and any weight-related health conditions to give you personalised advice about 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.
What is a healthy BMI for UK adults?
According to NHS guidelines, a healthy BMI is between 18.5 and 24.9. If you're of South Asian, Black African, Black Caribbean, or Chinese heritage, the NHS recommends lower thresholds — 18.5 to 22.9 — because these groups face higher health risks at the same BMI levels.
How do I calculate my BMI if I use stone and pounds?
Convert your weight to kilograms first (1 stone = 6.35kg). Then divide your weight in kg by your height in metres squared. Our free weight converter above helps you switch between stone, pounds, and kilograms instantly.
Can BMI be inaccurate?
Yes. BMI doesn't account for muscle mass, so athletes may have a high BMI but low body fat. It also ignores age, bone density, and fat distribution. The NHS recommends using BMI alongside waist circumference and discussing your individual health with your GP.
What should I do if my BMI is outside the healthy range?
Book an appointment with your GP to discuss your health, family history, and any weight-related conditions. Your GP can advise on lifestyle changes, refer you to NHS weight management services if appropriate, or discuss other support options tailored to your needs.
Does BMI apply to children?
No. Children use age and sex-specific BMI centile charts, not adult categories. Use the NHS Healthy Weight Calculator for children, or ask your GP or health visitor for personalised guidance on your child's weight.
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.