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 essential tools for understanding your weight and overall health status. MyWeightCheck offers a suite of free, evidence-based health calculators designed specifically for UK adults, using stone, pounds, and kilograms. These tools provide instant insights aligned with NHS guidance, helping you track your healthy weight range, convert measurements, and monitor progress. Whether you're exploring weight management options or simply want to understand your BMI, our calculators offer practical, personalised information at no cost.
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.
What Health Calculators Can Tell You
Health calculators are screening tools that help you understand key health metrics. Our BMI calculator uses your height and weight to assess whether you fall into a healthy weight range according to NHS guidelines. The weight converter instantly translates between stone, pounds, and kilograms — essential for UK health information where doctors use kg but many adults prefer stone. We also offer a GLP-1 weight loss calculator to estimate potential weight loss with prescription medications, and a progress tracker to monitor changes over weeks and months. These tools are most useful when combined with professional advice from your GP, as they provide screening information rather than diagnosis.
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 Calculators Within NHS Health Advice
The NHS recommends using BMI as part of a broader assessment of weight health. Healthy weight UK adults should aim for a BMI between 18.5 and 24.9, though lower thresholds apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage. A calculator alone cannot replace professional assessment — weight is influenced by genetics, medical conditions, medications, and lifestyle factors. Use our tools to understand your starting point, then discuss results with your GP or a healthcare professional. For weight management support, the NHS health guide recommends tier 1 self-help, digital tools (like our calculators), and community programmes as first steps before considering specialist services or prescription options.
- 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.
Why should I use a health calculator?
Health calculators provide quick screening information aligned with NHS guidance. They help you understand your BMI category, convert between UK measurements, and track progress. They're not diagnostic but are useful first steps before speaking to your GP about weight health or management options.
Are these calculators accurate?
Our calculators use clinically standard formulas (NHS BMI categories, exact conversion ratios). However, BMI has limitations — it doesn't distinguish muscle from fat, doesn't account for ethnicity-specific thresholds, and isn't accurate during pregnancy. Use them as screening tools, not definitive health assessments.
Can a calculator tell me if I need weight loss treatment?
No. A calculator can show your BMI category, but eligibility for NHS weight management services or prescription medications requires assessment by a GP or specialist. They consider your full health picture, comorbidities, and individual circumstances.
What's the difference between your calculators and NHS tools?
MyWeightCheck calculators use the same NHS formulas and thresholds. Our tools are free, designed specifically for UK measurements, and include additional features like weight loss projections and progress tracking. They complement NHS guidance rather than replace it.
Can I use these calculators for children?
No. Child BMI uses age and sex-specific centiles, not adult categories. Always use the NHS Healthy Weight Calculator for children, or ask your health visitor or GP for guidance on your child's weight health.
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.