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 Weight Management
MyWeightCheck provides free, accessible health calculators designed specifically for UK adults using stone, pounds, and kilograms. Our suite of tools helps you understand your weight in the context of NHS healthy weight guidance, calculate your BMI accurately, convert between different measurement units, and estimate potential weight loss outcomes with GLP-1 medications like Mounjaro and Wegovy. All calculators are built on evidence-based formulas and aligned with current NHS health advice. Whether you're exploring your health metrics or considering weight management options, our calculators provide instant, personalised results without requiring personal information or payment.
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 Our Free Health Calculators Do
MyWeightCheck offers four core health calculation tools, each serving a different aspect of weight and health management:
- BMI Calculator — Enter your height and weight to instantly calculate your Body Mass Index and see where you fall on the NHS healthy weight scale. The calculator adjusts thresholds for different ethnic groups, recognising that South Asian, Chinese, Black African, and Black Caribbean adults face higher health risks at lower BMI levels.
- Weight Converter — Convert your weight between kilograms, stone, and pounds instantly. The converter uses exact conversion formulas and is ideal for understanding your weight across different measurement systems used in the UK, NHS clinics, and international health resources.
- GLP-1 Weight Loss Calculator — If you're considering prescription weight loss medications like Mounjaro or Wegovy, this tool estimates potential weight loss outcomes based on clinical trial data. It helps you understand what results might be realistic, acknowledging that individual outcomes vary significantly.
- Progress Tracker — Log your weight over time and visualise your progress with a simple, confidential tracking tool. Track weight loss journeys, monitor health improvements, and stay motivated with visual progress records.
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.
Why Use UK Health Calculators Instead of Generic Tools
Generic health calculators often use American measurements, outdated formulas, or don't account for UK-specific NHS healthy weight guidance. MyWeightCheck calculators are built specifically for UK adults and use:
- UK measurements — Stone, pounds, and kilograms as standard, reflecting how UK adults naturally think about weight.
- NHS thresholds — BMI categories and healthy weight ranges aligned with current NHS guidelines, not generic global standards.
- Ethnicity-adjusted data — Recognising that healthy weight thresholds differ for people of South Asian, Chinese, Black African, and Black Caribbean heritage.
- Current clinical evidence — Weight loss calculator data based on recent SURMOUNT and STEP clinical trials for GLP-1 medications.
All our tools are free, require no registration, and don't sell or store your personal data.
- 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 MyWeightCheck calculators accurate?
Yes. Our calculators use evidence-based formulas aligned with NHS guidelines. BMI uses the standard WHO formula, weight conversions use exact metric equivalents, and the GLP-1 calculator is based on data from the SURMOUNT-1 and STEP-1 clinical trials. However, all health information tools have limitations — always discuss your personal health with your GP.
Do the calculators work for children?
Our BMI calculator is designed for adults. Children's BMI is assessed differently using age and sex-specific centile charts. If you're concerned about your child's weight, speak to your GP or visit the NHS Healthy Weight Calculator for children.
What if my ethnicity isn't listed in the BMI calculator?
Our BMI calculator shows adjusted thresholds for South Asian, Chinese, Black African, and Black Caribbean adults. If your ethnicity isn't listed, use the standard NHS BMI categories. Your GP can advise on what a healthy weight range means for your individual circumstances.
Can I use these calculators to diagnose a health condition?
No. These calculators are informational tools only. They don't diagnose conditions or provide medical advice. A BMI result, for example, indicates whether your weight falls in a certain range — it doesn't diagnose obesity or any medical condition. Always consult your GP for personal health advice.
Are these calculators safe to use if I'm pregnant?
No. BMI and weight loss calculations are not appropriate during pregnancy. If you're pregnant or planning to become pregnant, speak to your midwife or GP about healthy weight management during pregnancy.
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.