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
Calculate BMI Weight Using NHS Guidelines
Your BMI (Body Mass Index) is a simple measurement that shows the relationship between your weight and height. Calculating your BMI weight is the first step to understanding whether you're in a healthy range according to NHS guidelines. The NHS uses standardised BMI categories to help identify whether excess weight might affect your health. Use our free BMI calculator above to find your personal BMI instantly, or read on to understand how the calculation works, what your result means, and when to seek help from 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.
NHS BMI Categories and What They Mean
The BMI formula is straightforward: divide your weight in kilograms by your height in metres squared (kg ÷ m²). For those using imperial measurements, the calculation is the same principle but expressed as (weight in lbs × 703) ÷ height in inches squared.
The NHS categorises BMI results into distinct ranges that help identify health risk:
- Below 18.5: Underweight — may need advice on nutrition
- 18.5–24.9: Healthy weight — the target range for most adults
- 25.0–29.9: Overweight — increased health risk begins here
- 30.0–34.9: Obese (Class I) — significant health concerns
- 35.0–39.9: Obese (Class II) — higher health risk
- 40.0+: Severely obese (Class III) — serious health implications
Important: If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds. Your healthy BMI range starts at 18.5 but overweight begins at 23.0 and obesity at 27.5, because these populations face higher health risks at lower BMI levels.
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.
NHS Weight Management and When to Seek Help
The NHS offers a structured pathway to help manage weight across four tiers. Tier 1 focuses on self-help using digital tools and community programmes — this is where your free BMI calculator helps you track your starting point. Tier 2 involves your GP, who can offer behaviour change support and structured weight loss programmes like the NHS Weight Loss Plan.
If you need more intensive support, your GP can refer you to Tier 3 specialist weight management services, where you may be assessed for prescription medication like Mounjaro or Wegovy alongside intensive lifestyle support. Tier 4 is bariatric surgery, reserved for severe obesity with serious health complications. Contact your GP if your BMI is consistently above 25, or if you have a healthy BMI range concern — they can provide personalised guidance and check for underlying health conditions.
- 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 a healthy BMI according to the NHS?
For most UK adults, a healthy BMI is between 18.5 and 24.9. However, NHS guidance recommends lower thresholds for South Asian, Chinese, Black African, and Black Caribbean adults (18.5–22.9), as these populations have higher health risks at lower BMI levels. Use our BMI calculator to check your personal result instantly.
How do I calculate my BMI weight manually?
Divide your weight in kilograms by your height in metres squared. For example, if you weigh 70kg and are 1.73m tall: 70 ÷ (1.73 × 1.73) = 70 ÷ 2.99 = 23.4 BMI. This falls in the healthy weight range. Our calculator does this instantly.
What are the limitations of BMI?
BMI doesn't distinguish between muscle and fat — athletes may have a high BMI but low body fat. It also ignores where fat is stored (waist circumference matters for health) and may be less accurate for elderly people, very muscular individuals, or during pregnancy. Your GP can assess these factors.
When should I ask my GP about my BMI weight?
Contact your GP if your BMI is consistently above 25, if you have weight-related health concerns like high blood pressure or joint pain, or if you're struggling to manage your weight despite lifestyle changes. They can check for underlying health conditions and discuss the NHS weight management pathway.
Does NHS offer prescription medication for weight management?
Yes. If your BMI is 30 or above (or 27+ with weight-related health conditions), your GP can refer you to specialist NHS Tier 3 weight management services. Here you may be assessed for medications like Mounjaro or Wegovy, used alongside reduced-calorie diet and exercise. Access varies by region and waiting lists apply.
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.