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 — Check Your Healthy Weight Range
A BMI calculator helps you understand whether your weight falls within a healthy range according to NHS guidelines. BMI (body mass index) is a simple screening tool that uses your height and weight to estimate body composition. Our free BMI calculator on this page gives you an gradual improvement and explains what your BMI means for your health. It's a quick first step towards understanding your weight and taking control of your 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 Does a BMI Calculator Work?
A BMI calculator uses a straightforward formula: your weight in kilograms divided by your height in metres squared. The result places you into one of five categories according to NHS guidelines:
- Underweight: BMI below 18.5
- Healthy weight: BMI 18.5 to 24.9
- Overweight: BMI 25.0 to 29.9
- Obese (Class I): BMI 30.0 to 34.9
- Severely obese: BMI 40.0 and above
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — a healthy weight range starts at 18.5 and extends only to 22.9. This is because these groups face higher health risks from type 2 diabetes and cardiovascular disease at the same BMI levels as other populations. The calculator takes these variations into account and provides personalised guidance based on your ethnic background.
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.
Why Use a BMI Calculator?
A BMI calculator is a useful first screening tool for understanding your weight health. It helps you identify whether lifestyle changes, exercise, or weight management support might benefit you. However, BMI has limitations — it does not distinguish between muscle and fat, so athletes or very muscular individuals may have a high BMI despite low body fat. Use our free weight converter and progress tracker alongside the BMI calculator to monitor your weight journey in both metric and imperial measurements. For personalised health advice, your GP can assess your individual circumstances and recommend appropriate next steps.
- 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 range for UK adults?
According to NHS guidelines, a healthy BMI is between 18.5 and 24.9 for most adults. If you are of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a healthy range of 18.5 to 22.9. Your GP can explain what this means for your individual health.
Can I use a BMI calculator if I am pregnant?
BMI is less accurate during pregnancy as weight gain is essential for fetal development. Pregnant women should speak with their midwife or GP about healthy weight management during pregnancy rather than relying on standard BMI categories.
Is BMI calculator accurate for children?
No — BMI categories for adults do not apply to children. Children's BMI is assessed using age and sex-specific growth charts. The NHS recommends parents use the NHS Healthy Weight Calculator for children or speak with their GP or health visitor.
What should I do if my BMI is in the overweight or obese range?
A BMI in the overweight or obese range suggests discussing weight management options with your GP. Small lifestyle changes such as increasing activity, reducing calorie intake, or joining a structured weight loss programme can help. Your GP may also discuss whether prescription weight loss medication might be suitable.
Does muscle mass affect my BMI calculator result?
Yes — BMI does not distinguish between muscle and fat. Very muscular individuals may have a high BMI but low body fat. If you are very active or have significant muscle mass, speak with your GP about whether BMI is the most appropriate measure for you.
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.