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
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Figuring Out Your Ideal Body Weight in the UK
There's no single "ideal" body weight that applies to everyone — it depends on your height, age, muscle mass, and overall health. In the UK, the NHS uses BMI (body mass index) as the primary screening tool for healthy weight, with a healthy BMI range of 18.5 to 24.9 for most adults. However, several formulas and guidelines can help you understand what weight management might look like for your individual circumstances. This guide explains the different approaches to determining a healthy weight for you, using UK health advice and evidence-based information.
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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 Guidelines and Healthy Weight Ranges in the UK
The NHS defines a healthy weight through BMI ranges, which vary slightly depending on your ethnic background. For most UK adults, a healthy BMI is between 18.5 and 24.9. However, for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower threshold — a healthy BMI of 18.5 to 22.9 — because these groups face higher risk of type 2 diabetes and cardiovascular disease at the same BMI as other populations.
To find your healthy weight range, you can use our free BMI calculator on this page, which instantly shows you the weight range that corresponds to a healthy BMI for your height. Beyond BMI, the NHS also emphasises that waist circumference matters. Men should aim for a waist under 94cm (37 inches), and women under 80cm (31.5 inches), as fat stored around the abdomen increases health risks regardless of overall BMI.
- Healthy BMI range: 18.5–24.9 (for most adults)
- Lower threshold for South Asian/Black African/Caribbean/Chinese adults: 18.5–22.9
- Waist circumference is also important for health risk assessment
- Even a 5% reduction in body weight can improve health outcomes
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.
Formulas for Estimating Ideal Body Weight
Several mathematical formulas exist to estimate an "ideal" body weight, though these are reference points rather than prescriptive targets. The Devine Formula is widely used in clinical practice: for men, it's 50kg plus 2.3kg per inch over 5 feet; for women, it's 45.5kg plus 2.3kg per inch over 5 feet. The Robinson Formula offers a slightly different calculation. However, these formulas don't account for muscle mass, bone density, or individual variation in frame size.
The key point is that ideal weight varies significantly between individuals. An athlete with high muscle mass may have a higher BMI than recommended but excellent health, whilst someone at a "healthy" BMI may have other health risk factors. Use our free weight converter to check your current weight in both kg and stone, then discuss your personal ideal weight range with your GP, who can consider your full health picture.
- 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 a healthy weight and an ideal weight?
A healthy weight range is based on BMI and health outcomes (typically 18.5–24.9 BMI). An "ideal" weight is more subjective and varies by individual, accounting for muscle mass, frame size, and personal goals. Your GP can help determine what's healthy specifically for you.
How do I calculate my healthy weight range for my height?
Use the free BMI calculator on this page — enter your height and it shows the weight range for a healthy BMI. For example, at 5ft 8in, a healthy weight is roughly 55–74kg (8st 10lbs to 11st 10lbs). This reflects UK NHS guidelines.
Why are BMI thresholds different for people from South Asian or Black African backgrounds?
The NHS recommends lower BMI thresholds (18.5–22.9) for these groups because they face higher cardiovascular and diabetes risk at the same BMI as other populations. This is based on clinical evidence and means health screening should account for ethnicity.
Does ideal body weight account for muscle mass?
No — BMI and weight-based formulas don't distinguish between muscle and fat. A muscular person may have a higher BMI but lower body fat percentage. This is why your GP may assess waist circumference and overall health, not just weight alone.
Should I aim for the lower or upper end of the healthy BMI range?
The entire healthy BMI range (18.5–24.9) is associated with good health outcomes. Where within that range is right for you depends on your genetics, activity level, and health goals. Your GP can advise on a realistic, sustainable target weight for your circumstances.
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.