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 Checker — Your UK Health Guide
A BMI checker is a simple tool that calculates your body mass index — a key health screening measure used by the NHS. Your BMI helps determine whether your weight falls within a healthy range for your height. In the UK, understanding your BMI is the first step towards better health awareness. Our free BMI calculator instantly shows you your personal BMI, how it compares to NHS guidelines, and what it means for your wellbeing. Whether you're checking your weight management progress or exploring your healthy weight range, knowing your BMI provides valuable context for conversations with your GP.
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 a BMI Checker and Understand Your Result
Using a BMI checker is straightforward. You simply enter your height and weight, and the tool calculates your BMI using the formula: weight (kg) ÷ height (m)². The result falls into one of several NHS categories:
- Under 18.5: Underweight
- 18.5 to 24.9: Healthy weight
- 25.0 to 29.9: Overweight
- 30.0 to 34.9: Obese (Class I)
- 35.0 to 39.9: Obese (Class II)
- 40.0 and above: Severely obese (Class III)
It's important to remember that BMI has limitations — it doesn't distinguish between muscle and fat, so athletes may have a higher BMI despite being fit. Your GP can provide personalised context about what your BMI means for your individual health. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds, with a healthy weight range of 18.5 to 22.9.
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.
UK Health Resources and Next Steps
Once you've checked your BMI, the next step depends on your result. If you fall within the healthy weight range (18.5 to 24.9), maintaining your current weight through balanced nutrition and regular physical activity is key. If your BMI suggests you're overweight or obese, your GP can discuss personalised weight management options, which may include lifestyle changes, dietary support, or in some cases, prescription weight loss medications for eligible individuals.
The NHS recommends sustainable weight loss at a rate of 0.5 to 1 kg per week. You can complement your BMI checker insights with our free weight converter to track progress in your preferred units (stone, lbs, or kg), and use our progress tracker to log your weight management journey over time.
- 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 the difference between BMI and body fat percentage?
BMI is a screening tool based on height and weight only, whilst body fat percentage measures the actual proportion of fat in your body. BMI doesn't account for muscle mass — a muscular person may have a high BMI but low body fat. Your GP can discuss which measures are most relevant for your health.
Is BMI accurate for everyone in the UK?
BMI is useful for screening but has limitations. It's less accurate for athletes, elderly people, and pregnant women. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds due to higher health risks at the same BMI levels.
What should I do if my BMI shows I'm overweight?
A BMI in the overweight range (25 to 29.9) suggests lifestyle changes may help. Aim for 0.5 to 1 kg weight loss per week through balanced eating and activity. Your GP can offer personalised advice and may refer you to NHS weight management services if needed.
Can I lose weight too quickly?
Losing more than 1 to 1.5 kg per week is not recommended without medical supervision, as it increases muscle loss risk. The NHS recommends sustainable weight loss at 0.5 to 1 kg per week. If you're losing weight faster, discuss this with your GP.
How often should I check my BMI?
Monthly checks are reasonable if you're actively managing your weight. For general health monitoring, checking every 3 to 6 months is sufficient. Use our free BMI calculator above to track changes alongside our progress tracker for a fuller picture of your health 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.