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 for UK Adults — Complete Guide
Health calculators are free online tools that help you understand your weight and health status using NHS thresholds. MyWeightCheck offers several calculators including a BMI calculator, weight converter, and GLP-1 weight loss calculator designed specifically for UK measurements like stone, pounds, and kilograms. These tools give you instant results and context about your healthy weight range according to NHS guidance. They're educational resources to support your weight management journey, not medical advice. Always consult your GP for personalised health recommendations.
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 Health Calculators Work
Health calculators use simple formulas based on your personal measurements to provide health insights. Our BMI calculator uses your height and weight to calculate your Body Mass Index — a screening tool recognised by the NHS. Your BMI is compared against NHS categories: underweight (below 18.5), healthy weight (18.5–24.9), overweight (25.0–29.9), obese (30.0+), or higher categories. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply because these groups face higher health risks at lower BMI levels.
Our weight converter instantly translates between kilograms, stone, and pounds — the measurements most UK adults use daily. The GLP-1 weight loss calculator estimates potential weight loss based on clinical trial data if you're considering prescription weight loss treatment. All calculators use evidence-based formulas aligned with NHS health advice.
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.
Who Can Use These Tools and How to Access
MyWeightCheck calculators are free and open to all UK adults. You need your current height and weight — most people already know these measurements. Simply input your details, and you'll get instant results with NHS context. For the GLP-1 weight loss calculator, you'll also enter your BMI to see estimated outcomes based on clinical trial data. Results are personalised to your measurements and UK health guidelines.
These tools support your uk health information and weight management decisions, but they're not a substitute for medical advice. If you have health concerns or want personalised guidance, discuss your results with your GP. They can provide NHS health advice specific to your circumstances and help you plan next steps toward achieving a healthy weight.
- 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.
What is a BMI calculator and why use it?
A BMI calculator measures your Body Mass Index using your height and weight. The NHS uses BMI as a screening tool to identify whether you're in a healthy weight range. Our calculator aligns with NHS thresholds and includes ethnicity-adjusted categories for adults of South Asian, Chinese, Black African, or Black Caribbean heritage. It's a quick way to understand your weight status, though BMI has limitations — it doesn't distinguish muscle from fat or account for where fat is stored.
How accurate are online health calculators?
Online calculators like ours are accurate when you input correct measurements. They use evidence-based formulas recognised by the NHS. However, they provide screening information, not diagnosis. BMI, for example, is useful but has limitations — athletes may have high BMI despite low body fat. Always confirm results with your GP, especially if you have health concerns or unusual measurements.
Can I use these calculators if I'm pregnant or have health conditions?
Standard BMI calculators aren't suitable for pregnancy because BMI thresholds change during pregnancy. If you're pregnant, speak to your midwife or GP about your healthy weight range. Similarly, people with certain health conditions should discuss their results with their GP rather than relying on calculator results alone. Healthcare professionals can give you personalised advice.
Are MyWeightCheck calculators free to use?
Yes, all MyWeightCheck calculators are completely free — our BMI calculator, weight converter, GLP-1 weight loss calculator, and progress tracker require no payment or account. We're an independent UK health information website providing free tools to support your understanding of weight and health. There are no hidden costs or subscriptions.
What should I do after using a health calculator?
Use your calculator results as a starting point for conversation with your GP or healthcare professional. If your BMI falls outside the healthy range, or if you're interested in weight loss support, your GP can discuss options aligned with NHS guidance. They may refer you to weight management services or discuss whether prescription treatments like GLP-1 medications are appropriate for you.
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.