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 to Calculate Your Body Weight — UK Health Guide
Calculating body weight accurately is the first step towards understanding your health. In the UK, we measure weight in stone and pounds or kilograms, and understanding how to calculate and interpret your weight is essential for assessing whether you fall within a healthy weight range according to NHS guidance. This guide explains the different methods, UK measurements, and tools available to help you track your weight effectively.
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 Calculate and Track Body Weight in the UK
Calculating body weight starts with accurate measurement using reliable scales. Weighing yourself at the same time each day (preferably morning, after using the toilet but before eating) gives the most consistent results. The NHS recommends checking your weight weekly rather than daily, as daily fluctuations due to water retention and food intake can be misleading.
- Use scales that measure to the nearest 0.1 kg or 0.2 lbs for accuracy
- Wear minimal clothing for consistency
- Record your weight in both kg and stone using our free weight converter
- Track changes over weeks and months, not days
- Remember that weight naturally fluctuates by 1–2 kg day-to-day due to hydration and digestion
Once you have your weight, use our free BMI calculator above to determine where you fall on the healthy weight scale according to NHS health guidance. This gives you a baseline for understanding your personal weight management context.
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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.
Healthy Weight Ranges and BMI Context
The NHS defines healthy weight using Body Mass Index (BMI), which calculates whether your weight is appropriate for your height. A healthy BMI falls between 18.5 and 24.9 for most UK adults. However, BMI has limitations — it doesn't distinguish between muscle and fat, so athletes may have a higher BMI despite being very fit. 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 level.
Beyond just calculating body weight, the NHS also recommends measuring waist circumference: over 94 cm (37 inches) in men or 80 cm (31.5 inches) in women indicates increased health risk. Our free BMI calculator on this page provides your personal healthy weight range instantly — use it alongside the weight converter to switch between kg, stone, and pounds for your preferred UK measurements.
- 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 measure and calculate my body weight at home?
Weigh yourself on reliable scales at the same time each day, preferably in the morning after using the toilet but before eating. Wear minimal clothing for consistency. Record your weight weekly rather than daily. Use our free weight converter to switch between kg, stone, and pounds, whichever you prefer for UK health tracking.
How do I know if my calculated weight is healthy for my height?
Use our free BMI calculator above — enter your height and weight to find your BMI instantly. The NHS defines a healthy BMI as 18.5 to 24.9. Your result also shows your personalised healthy weight range in both kg and stone, helping you understand what healthy weight management means for you specifically.
Why does my calculated weight fluctuate so much day-to-day?
Daily weight changes of 1–2 kg are normal due to water retention, food in your digestive system, and hormonal changes. This is why the NHS recommends tracking weight weekly rather than daily. Look for trends over weeks and months instead of focusing on single-day changes.
Is BMI the only way to calculate whether my weight is healthy?
No. While BMI is the NHS screening tool, waist circumference is equally important — excess abdominal fat carries higher health risks. Additionally, BMI doesn't account for muscle mass, so athletes may have a higher BMI despite being very fit. Your GP can discuss your individual health context.
How can I track my calculated weight over time?
Record your weight weekly in the same units (kg or stone). Use our free progress tracker on MyWeightCheck to log your weight and visualise trends over weeks and months. This helps you see real progress beyond daily fluctuations and stay motivated with evidence-based tracking.
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.