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
Weight Calculator — Your NHS-Aligned UK Health Tool
A weight calculator is an essential tool for understanding your health status in the UK. Whether you want to check your BMI, convert between stone and kilograms, or discover your healthy weight range, our free weight calculator and related health tools help you make informed decisions about your weight management. The NHS recommends using your BMI as a starting point, alongside other health measurements, to assess whether your weight falls within a healthy range for your height and age.
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 NHS Weight Guidelines Work in the UK
The NHS provides clear guidance on healthy weight ranges for UK adults. Your BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in metres squared. A healthy BMI falls between 18.5 and 24.9 according to NHS standards. However, the NHS also recognises that people from South Asian, Chinese, Black African, and Black Caribbean backgrounds have higher health risks at lower BMI levels, so recommended thresholds start at 18.5–22.9 for these groups.
The NHS emphasises that BMI is a screening tool, not a diagnosis. It doesn't account for muscle mass, bone density, or where fat is stored. That's why your GP may also assess your waist circumference (men over 94cm, women over 80cm indicates increased health risk). Use our free BMI calculator above to check your personal BMI instantly, and our weight converter to switch between kilograms, stone, and pounds.
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.
Weight Management Tools and Next Steps in the UK
Once you've used a weight calculator to understand your current position, the next step is deciding on an appropriate action. The NHS recommends a sustainable weight loss rate of 0.5–1 kg per week, achieved through a reduced-calorie diet and increased physical activity. For those with a BMI over 30, or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea), prescription options including GLP-1 weight loss injections may be considered following a clinical assessment with your GP or specialist service.
Track your progress using our free progress tracker, or try our GLP-1 weight loss calculator to explore potential outcomes. Always consult your GP before starting any weight loss programme or considering medication.
- 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 a weighting calculator and why do I need one?
A weight calculator helps you understand your health status by converting your weight between different units (kg, stone, lbs) and calculating your BMI. It's useful because the UK predominantly uses stone for everyday weight, but NHS health guidance uses kilograms and BMI. A calculator instantly shows you where your weight sits relative to NHS healthy ranges.
What's the difference between BMI and healthy weight range?
BMI is a screening ratio of weight to height (18.5–24.9 is healthy for most adults). Your healthy weight range is the band of actual weights that produce a healthy BMI for your specific height. For example, at 5ft 8in, the healthy weight range is approximately 55–74 kg (8st 10lbs–11st 10lbs). Use our BMI calculator to find your personal range.
Is BMI accurate for everyone?
BMI is a useful screening tool but has limitations. It doesn't distinguish between muscle and fat, so athletes may have a high BMI despite low body fat. It also doesn't account for age, bone density, or where fat is stored. Your GP considers BMI alongside waist measurement and other health factors for a complete picture.
Can I use a weight calculator if I'm from a South Asian or Black African background?
Yes, but the thresholds are different. The NHS recommends South Asian, Chinese, Black African, and Black Caribbean adults use a healthy BMI range of 18.5–22.9 (not 18.5–24.9) because these groups face higher risks of type 2 diabetes and heart disease at lower BMI levels. Always discuss your personal health with your GP.
What should I do after checking my weight with a calculator?
If your BMI is in the healthy range, maintain your current lifestyle. If it's above 25, consider speaking to your GP. The NHS recommends sustainable weight loss of 0.5–1 kg per week through diet and activity. For BMI over 30, your GP may refer you to specialist weight management services or discuss prescription options like GLP-1 injections following clinical assessment.
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.