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 UK Health Calculators — Your Wellness Tools
Health calculators are essential tools for understanding your weight, BMI, and potential health outcomes. MyWeightCheck provides free UK health calculators designed specifically for British measurements and NHS guidance. Whether you want to check your BMI using the standard NHS categories, convert your weight between kg, stone, and pounds, or explore how GLP-1 weight loss medications might help you, our suite of free health tools gives you instant, personalised insights. All tools are aligned with current UK health thresholds and are completely free to use.
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 translate your personal measurements into actionable health information. A BMI calculator uses your weight and height to determine whether you fall into the healthy weight range, overweight, or obese categories according to NHS guidance. The BMI categories are: healthy weight (18.5–24.9), overweight (25–29.9), and obese (30 and above). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, NHS recommends lower thresholds starting at BMI 23 for overweight status.
A weight converter helps you switch between kilograms, stone, and pounds—essential since UK adults typically use stone and pounds, whilst clinical settings use kg. A GLP-1 weight loss calculator projects potential weight loss outcomes if you were to use prescription medications like Mounjaro or Wegovy, based on clinical trial data. These calculators work alongside nhs health advice to give you a clearer picture of where you stand health-wise.
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 UK Health Calculators Safely
Remember that calculators provide screening information, not medical diagnosis. A BMI reading is useful but has limitations—it doesn't distinguish between muscle and fat, and doesn't account for where fat is stored. Your GP can give you personalised interpretation of your results and recommend next steps.
When using a weight management calculator, understand that individual results vary significantly. Clinical trials show average outcomes, but your personal journey depends on adherence, lifestyle, genetics, and overall health. Always consult your GP before starting any weight loss programme or considering prescription medications. Use calculator results to start a conversation with your healthcare provider, not as a substitute for professional advice.
- 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 these UK health calculators accurate?
Yes, all MyWeightCheck calculators use NHS-aligned formulas and clinically validated data. The BMI calculator uses the standard formula: weight (kg) ÷ height (m)². Weight converters use precise conversion rates. GLP-1 calculators are based on STEP and SURMOUNT clinical trial data. However, calculators provide screening information only—your GP can give personalised interpretation.
What's the difference between BMI and body composition?
BMI measures weight relative to height and doesn't distinguish muscle from fat. A muscular athlete might have a high BMI but low body fat. Body composition analysis is more detailed but requires specialist equipment. Use our BMI calculator as a starting point, then discuss results with your GP for a fuller picture of your health.
Can I use these calculators to diagnose a health condition?
No. These are screening tools only and do not diagnose any medical condition. They help you understand whether your weight falls within NHS healthy ranges and can prompt a conversation with your GP. Always consult a healthcare professional for diagnosis and personalised health advice.
What if I'm pregnant or breastfeeding?
BMI categories don't apply during pregnancy or breastfeeding. Our BMI calculator is designed for non-pregnant adults. If you're pregnant or breastfeeding and want to discuss your weight, speak with your GP, midwife, or health visitor who can provide guidance suited to your situation.
How often should I use a weight calculator?
You can use weight converters anytime you need to switch between units. For BMI and weight loss calculators, checking monthly or quarterly is reasonable if you're actively managing your weight. More frequent checking can create unhelpful focus on daily fluctuations. Sustainable health is a long-term process—calculators are tools to track progress, not daily metrics.
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.