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
How Do You Calculate Weight in the UK?
Calculating your weight is more than just reading a number on the scales. In the UK, we typically measure body weight in stone and pounds, but understanding what that weight means for your health requires context — your height, age, and individual health circumstances all matter. The NHS provides clear guidance on healthy weight ranges, and several calculation methods help you assess whether your current weight falls within a healthy range for your height. This guide explains the main approaches used in UK health advice.
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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.
Common Weight Calculation Methods in the UK
The most widely used method in UK weight management is BMI (Body Mass Index), which calculates the relationship between your weight and height. The formula is simple: divide your weight in kilograms by your height in metres squared. For example, someone weighing 70kg and 1.73m tall would have a BMI of approximately 23.4, which falls within the healthy weight range according to NHS guidance.
- Healthy weight range: BMI 18.5–24.9 (NHS standard)
- Overweight: BMI 25.0–29.9
- Obese: BMI 30.0 and above
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds because these groups face higher health risks at the same BMI. Use our free BMI calculator above to check your personal BMI instantly — it accepts both metric and imperial measurements, making it simple to get your result in UK context. Another useful measurement is waist circumference; for men, over 102cm (40 inches) indicates high health risk, whilst for women, over 88cm (34.5 inches) is concerning, regardless of BMI.
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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 Guidance and UK Health Information
The NHS provides clear UK health advice on what constitutes a healthy weight for adults. Rather than giving a single "ideal" number, the NHS focuses on healthy weight ranges based on height and BMI. You can calculate your healthy weight range using the formula: a healthy BMI of 18.5–24.9 multiplied by your height in metres squared.
For practical support, the NHS Weight Loss Plan offers a free digital tool and guidance for managing weight sustainably. If you're concerned about your weight or have underlying health conditions, your GP can provide personalised advice and may refer you to a specialist weight management service. Our free weight converter helps you switch between kg, stone, and pounds — essential for understanding your weight in the units you're familiar with and comparing it to NHS guidance, which often uses kilograms.
- 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 best way to calculate a healthy weight for my height in the UK?
The NHS recommends using BMI (Body Mass Index) as your primary guide. Calculate it by dividing your weight in kg by your height in metres squared. A healthy BMI range is 18.5–24.9. For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds apply. Your GP can provide personalised guidance based on your individual health.
How do I convert my weight to stone if I only know kilograms?
Divide your weight in kilograms by 6.35. For example, 70kg ÷ 6.35 = approximately 11 stone. Our free weight converter tool on this page does this instantly — simply enter your weight and select your preferred units for accurate UK measurements.
Is BMI the only way to assess if my weight is healthy?
BMI is useful but has limitations — it doesn't distinguish between muscle and fat. The NHS also recommends measuring waist circumference: men should aim for under 94cm (37 inches), women under 80cm (31.5 inches). Combined with BMI, waist measurement gives a clearer picture of health risk.
What weight loss rate is recommended by the NHS?
The NHS recommends losing weight at a rate of 0.5–1 kg (1–2 pounds) per week for sustainable, healthy weight loss. This typically requires a calorie deficit of around 500 kcal per day. Faster weight loss should only be attempted under medical supervision.
Should I calculate my weight differently if I'm over 50 or have health conditions?
Age and health conditions affect how to interpret your weight, but BMI calculation remains the same. However, your GP may recommend adjustments based on muscle mass, bone density, or specific conditions. Always consult your GP for personalised advice about what your weight means for your individual health.
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.