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
Free Health Calculators for UK Adults
Health calculators are straightforward tools that help you understand your weight, BMI, and health metrics using UK measurements. Whether you're converting weight between stone and kilograms, checking your BMI against NHS guidelines, or exploring weight loss options, free online calculators provide instant, evidence-based results. MyWeightCheck offers several free calculators designed specifically for UK adults, aligned with NHS healthy weight guidance and using familiar measurements like stone and pounds.
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.
Understanding UK Health Calculators and NHS Guidance
The NHS recommends using BMI as a screening tool for healthy weight, though it has limitations — it doesn't distinguish between muscle and fat. A healthy BMI range is 18.5 to 24.9 for most UK adults; for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower threshold of 18.5 to 22.9 due to higher health risks at lower BMI levels.
Our free BMI calculator above provides your personal BMI instantly using your height and weight in UK measurements (stone, pounds, or kilograms). Beyond BMI, waist circumference also matters — the NHS advises that men's waist over 94cm (37 inches) and women's waist over 80cm (31.5 inches) indicate increased cardiovascular risk.
- Healthy weight range: BMI 18.5–24.9 for most adults
- Overweight: BMI 25–29.9
- Obese: BMI 30 or above
- Ethnicity adjustment: Lower thresholds for South Asian and Black African backgrounds
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.
Using Free Calculators Alongside GP Advice
Free health calculators are helpful starting points, but they're not substitutes for personalised medical advice. If your BMI suggests you're outside a healthy range, or if you're concerned about your weight and health, speak with your GP. They can assess your individual circumstances, discuss any underlying health conditions, and advise on weight management options — whether lifestyle changes, NHS specialist services (tier 3 weight management), or prescription medication if appropriate.
Our weight converter tool helps you switch between kilograms, stone, and pounds — useful if you need to compare your weight against NHS healthy weight charts or understand your results in familiar UK measurements. Track your progress with our free progress tracker as you work towards your health goals.
- 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 healthy BMI in the UK?
According to NHS guidance, a healthy BMI is between 18.5 and 24.9 for most UK adults. However, adults of South Asian, Chinese, Black African, or Black Caribbean heritage should aim for 18.5 to 22.9 due to higher health risks at the same BMI. Your GP can advise on what's healthy for you personally.
How accurate are free online health calculators?
Free calculators like BMI tools are accurate if you enter correct measurements. However, BMI has limitations — it doesn't account for muscle mass, age, or where fat is stored. Waist measurement is also important. Use calculators as a guide, not a diagnosis. Always consult your GP for personalised advice.
Can I use a calculator to check if I need weight loss treatment?
A BMI calculator is a useful first step. If your BMI suggests overweight or obesity (BMI 25+) and you have weight-related health conditions, you may be eligible for support. Our GLP-1 weight loss calculator can help estimate potential outcomes. However, eligibility for prescription medication requires assessment by your GP or a healthcare professional.
Why do UK health calculators use stone and pounds?
Most UK adults use stone and pounds for body weight, even though the NHS uses kilograms clinically. Our calculators offer both metric and imperial measurements so you can use whichever feels more familiar. Use our weight converter to switch between units instantly.
Should I use a calculator instead of seeing my GP about weight?
Calculators provide useful information but aren't a replacement for medical advice. If you're concerned about your weight, health, or eligibility for weight management support, speak with your GP. They can discuss NHS services, lifestyle changes, and treatment options tailored to your health needs.
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.