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
Understanding Health Calculators for UK Weight Management
Health calculators are free online tools that help you understand your weight, BMI, and potential health outcomes based on your personal measurements. In the UK, these calculators use metric and imperial units—kilograms, stone, and pounds—making them practical for everyday use. Whether you're checking your BMI against NHS guidelines, converting your weight between units, or exploring weight loss options, health calculators provide instant, evidence-based results. They're not medical advice, but they're a helpful first step in understanding your health and deciding whether to speak with your GP.
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 UK Health Calculators Support Weight Management
The most common UK health calculators include BMI calculators, which measure your weight relative to your height and compare it against NHS guidelines. Our free BMI calculator instantly shows whether your measurement falls into the healthy weight, overweight, or obese category—with ethnicity-adjusted thresholds for adults of South Asian, Chinese, Black African, or Black Caribbean heritage.
- Weight converters switch between kg, stone, and pounds—essential because UK adults use stone, but NHS clinical records use kilograms
- GLP-1 weight loss calculators estimate potential weight loss at different doses of Mounjaro or Wegovy, based on clinical trial data
- Healthy weight range calculators show the ideal weight band for your height according to NHS thresholds
These tools are complementary to professional medical advice, not replacements for it. Use our free BMI calculator above to get your personal BMI instantly, then share the result with your GP if you have concerns about your health.
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.
When to Use Calculators and When to See Your GP
Health calculators are most useful as a screening and awareness tool. They help you understand your starting point and track progress over time using our free progress tracker. However, they should never replace professional medical advice.
See your GP if: your BMI is 25 or above with health concerns, you're interested in prescription weight loss medication, you have symptoms like fatigue or joint pain, or you want personalised nhs health advice based on your medical history. Your GP can assess your individual situation, review your medications, and discuss whether interventions like Mounjaro, Wegovy, or lifestyle changes are appropriate for you. Use the weight converter and BMI calculator on this page to gather your measurements before your appointment—it helps your GP understand your starting point.
- 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.
Are UK health calculators accurate?
Health calculators are accurate for what they measure—BMI, weight conversions, and rough weight loss projections based on clinical trials. However, they have limits. BMI doesn't distinguish between muscle and fat, and weight loss predictions vary by individual. They're screening tools, not diagnostic tools. Always discuss results with your GP for personalised interpretation.
What's the difference between a UK BMI calculator and a US one?
UK BMI calculators use the same formula but compare results against NHS thresholds and often include ethnicity-adjusted categories. US calculators use MHRA guidelines. The calculation itself is identical, but UK guidance recognises that South Asian and Black African adults face higher health risks at lower BMI levels—reflected in adjusted thresholds on UK calculators.
Can I use a health calculator to replace my GP visit?
No. Health calculators provide useful information but are not medical assessments. They can't diagnose conditions, review your medications, or assess whether prescription treatments are safe for you. Use calculators to understand your baseline, then discuss results with your GP. Only a qualified healthcare professional can prescribe medications like Mounjaro or Wegovy after a clinical assessment.
How often should I use a weight or BMI calculator?
Weekly or monthly tracking is reasonable if you're actively managing your weight. Our free progress tracker helps you log measurements over time and spot trends. Daily weighing can be misleading due to fluid fluctuation. Monthly checks are ideal for sustainable weight management—they show genuine progress without obsessive monitoring.
What should I do if my BMI calculator shows I'm overweight?
A high BMI reading means it's worth speaking with your GP, especially if you have other health concerns like joint pain, high blood pressure, or fatigue. Your GP can assess your overall health, discuss whether weight management is appropriate, and explain options—which might include lifestyle changes, NHS weight management programmes, or prescription medications. Not everyone with a high BMI needs to lose weight, but it's worth a conversation.
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.