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
Count and Calculate Your Way to Better Health in the UK
Counting and calculating are at the heart of effective health management in the UK. Whether you're tracking calories for weight loss, calculating your BMI, or working out a healthy weight range for your height, having the right tools and knowledge makes all the difference. This guide explains the key calculations used in NHS health guidance, how to use them correctly, and where to find free UK health information to support your wellness journey.
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.
Essential Health Calculations and NHS Guidance
BMI (Body Mass Index) is the most widely used health calculation in the UK. The formula is straightforward: divide your weight in kilograms by your height in metres squared (kg ÷ m²). For example, a person weighing 70kg and 1.73 metres tall would have a BMI of approximately 23.4, which falls within the healthy weight range of 18.5 to 24.9 according to NHS guidelines.
Calorie counting is another essential calculation for weight management. A deficit of around 500 calories per day typically results in losing approximately 0.5kg per week — the safe rate recommended by NHS guidance. However, BMI has limitations: it doesn't distinguish between muscle and fat, and ethnicity-adjusted thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults, who face higher health risks at lower BMI levels.
- Use our free BMI calculator above to check your personal BMI instantly
- Calculate your healthy weight range using the formula: 18.5 × height(m)² for the lower bound
- Track calories using established portion guides or a food tracking app
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.
Practical UK Health Tools and Resources
Calculating your own health metrics is empowering, but using reliable tools ensures accuracy. Our free weight converter allows you to switch between kg, stone, and pounds instantly — essential since the UK uses mixed measurements. Our BMI calculator removes the maths from the equation, giving you instant context against NHS healthy weight ranges.
For those interested in weight loss support, our GLP-1 weight loss calculator can help you understand potential outcomes if you're considering prescription weight loss medication alongside lifestyle changes. However, individual results always vary, and any health decision should involve your GP. Your healthcare provider can assess your personal circumstances, discuss your weight management options, and recommend whether prescription treatments or NHS weight management services are appropriate for you.
- 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 is the correct BMI calculation formula for UK adults?
BMI = weight (kg) ÷ height (m)². For example, someone weighing 75kg who is 1.70m tall would have a BMI of approximately 26. The NHS classifies this as overweight. Our free BMI calculator above does this instantly if you'd rather not calculate manually.
How many calories should I aim to lose per day for safe weight loss?
The NHS recommends a calorie deficit of around 500 calories per day, which typically results in losing approximately 0.5kg per week. This is considered safe and sustainable. Very gradual weight management (more than 1.5kg per week) should only be attempted under medical supervision.
Why do ethnicity-adjusted BMI thresholds matter in UK health guidance?
People of South Asian, Chinese, Black African, and Black Caribbean heritage have higher risk of type 2 diabetes and cardiovascular disease at lower BMI levels. The NHS therefore recommends lower thresholds for these groups: healthy weight starts at BMI 18.5–22.9 instead of 18.5–24.9, reflecting individual health risk.
How do I calculate my healthy weight range?
Multiply your height in metres by itself, then multiply by 18.5 (lower bound) and 24.9 (upper bound). For example, at 1.70m tall: lower = 18.5 × 2.89 = 53.5kg; upper = 24.9 × 2.89 = 71.9kg. Use our weight converter to switch between kg and stone.
Where can I get personalised health advice about my weight calculations?
Your GP is the best starting point for personalised guidance. They can assess your individual health, discuss your BMI in context, and recommend appropriate support — whether that's NHS tier 1–4 weight management services, referral to a specialist, or other options suited to 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.