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 Smart Calculator — NHS Guidelines for UK Adults
A BMI smart calculator helps you understand your weight in the context of NHS health recommendations. Using the BMI formula, it instantly shows whether your weight falls into the healthy range, overweight, or obese category according to NHS guidance. This page explains what your BMI means, how it's calculated, and what the NHS recommends next — whether you're looking to maintain a healthy weight or need support with weight management.
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. The NHS uses standardised BMI categories UK adults should aim for, though these vary slightly depending on ethnic background.
- Healthy BMI: 18.5 to 24.9 — the target range for most UK adults
- Overweight BMI threshold: 25.0 to 29.9 — increased health risks begin here
- Obese (Class I): 30.0 to 34.9
- Severely obese (Class II/III): 35.0 and above
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy BMI range is lower (18.5 to 22.9) because these groups face higher risk of type 2 diabetes and cardiovascular disease at standard BMI thresholds. Our free BMI calculator on this page automatically adjusts for ethnicity-specific guidance.
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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 Pathway and When to Seek Help
The NHS offers a structured weight management pathway through four tiers. Most people start at Tier 1 with self-help tools and the NHS Weight Loss Plan — both free resources. If you need more support, your GP can refer you to Tier 2 (community-based programmes) or Tier 3 (specialist multidisciplinary services where prescription weight loss medications may be considered). Understanding your BMI range UK helps identify which tier you might benefit from.
Use the free weight converter on this page to check your weight in kg, stone, and lbs — then use our BMI calculator to see where you fall. If your BMI is above 25, starting with the free NHS Weight Loss Plan is a good first step. Your GP can provide personalised guidance based on your individual health and circumstances.
- 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 are the NHS BMI categories for UK adults?
The NHS uses these 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 (Class III). For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds apply due to increased health risks at these BMI levels.
How does the BMI formula actually work?
The BMI formula divides your weight in kilograms by your height in metres squared (kg ÷ m²). For example, at 70kg and 1.75m tall, your BMI is 70 ÷ (1.75 × 1.75) = 22.9, which is in the healthy range. Our smart calculator above does this instantly — just enter your details.
What are the main BMI limitations I should know about?
BMI limitations include: it doesn't distinguish muscle from fat (athletes may have high BMI but low body fat), doesn't account for where fat is stored (waist measurement matters too), and is less accurate for elderly people, pregnant women, and children. Use it as a screening tool, not a definitive health measure.
What should I do if my BMI is above 25?
If your BMI is in the overweight or obese range, the NHS recommends starting with the free NHS Weight Loss Plan — a 12-week digital programme available on the NHS website. You can also speak to your GP, who may refer you to local weight management services. Losing even 5–10% of body weight can improve health outcomes.
Can ethnicity affect my healthy BMI range?
Yes. The NHS recommends lower BMI thresholds for people of South Asian, Chinese, Black African, or Black Caribbean heritage because these groups have higher risk of diabetes and heart disease at standard BMI levels. A healthy BMI for these groups is 18.5–22.9 rather than 18.5–24.9. Our calculator includes ethnicity-adjusted guidance.
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.