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
Health Calculators — Your NHS-Aligned UK Guide
Health calculators are practical tools that help UK adults understand their current health status and track progress towards wellness goals. Whether you're assessing your BMI, converting between weight measurements, or exploring weight management options, using reliable calculators aligned with NHS guidance gives you accurate, actionable information. MyWeightCheck provides free calculators specifically designed for UK measurements and health thresholds to support informed decisions about your health.
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.
NHS-Aligned Calculators for UK Health Assessment
The NHS recommends regular health monitoring using evidence-based tools that apply UK-specific guidance. Our free health calculators follow NHS standards and use UK measurements (stone, pounds, kilograms) to give you results that are immediately relevant to your healthcare.
- BMI Calculator: Assess your body mass index against NHS healthy weight categories (18.5–24.9). We include ethnicity-adjusted thresholds for South Asian, Chinese, Black African, and Black Caribbean adults, reflecting NHS recommendations that these groups face higher health risks at lower BMI levels.
- Weight Converter: Instantly convert between kg, stone, and pounds — the standard UK measurements your GP and NHS services use.
- GLP-1 Weight Loss Calculator: If you're exploring prescription weight management options like Mounjaro or Wegovy, our projection calculator helps estimate potential outcomes based on clinical trial data.
Each calculator provides personalised results in seconds, helping you understand where you stand and what healthy targets look like for your height and circumstances.
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 as Part of Your Health Journey
Calculators are most valuable when used as part of a broader health strategy rather than standalone snapshots. Your NHS GP can interpret your results in context of your medical history, family background, and individual risk factors. If your BMI falls into the overweight or obese category, or if you're considering weight management options, a calculator result is a good starting point for a conversation with your GP.
Use our free tools to track progress over time — logging your weight monthly and monitoring changes helps identify trends. Many people find that visible progress tracking motivates sustained lifestyle changes alongside any medical support. Your GP can refer you to specialist NHS weight management services if appropriate, or you can explore private options following clinical assessment by a UK-licensed prescriber.
- 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.
Which calculator should I use first?
Start with the BMI calculator — it gives you a quick snapshot of where your weight falls on the NHS healthy weight scale. From there, use the weight converter if you need to switch between metric and imperial, or explore the GLP-1 calculator if you're interested in understanding weight loss medication options.
Are these calculators accurate for all UK adults?
Our calculators use NHS-standard formulas and thresholds. However, they are screening tools, not diagnostic tools. BMI doesn't account for muscle mass or fat distribution, and individual health needs vary. Always discuss your results with your GP for personalised advice.
How often should I use the calculators?
Monthly weighing and recording is a good routine for tracking real progress. Weekly weighing can be demotivating due to normal water and hormonal fluctuations. Use the progress tracker to log your journey — seeing trends over weeks and months is more meaningful than daily changes.
Can I use these calculators for children?
Adult BMI categories do not apply to children — they use age and sex-specific growth charts instead. Always consult your GP or use the NHS Healthy Weight Calculator for children. These tools are designed for adults only.
What should I do after using the calculator?
If your result shows you're overweight or obese, book a GP appointment to discuss what it means for your health and what options are available. Your GP can refer you to NHS tier 3 weight management services, recommend lifestyle changes, or explore prescription options if clinically appropriate. These calculators are the starting point, not the end.
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.