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
Online Calculators for UK Health — Free Tools & Guidance
Online health calculators have become essential tools for UK adults managing their weight and understanding their health. MyWeightCheck provides free, easy-to-use calculators designed specifically for UK measurements—stone, pounds, and kilograms—aligned with NHS health thresholds and guidance. Whether you're checking your BMI, converting weight units, or exploring weight management options, our suite of online calculators helps you make informed health decisions without any cost or obligation.
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 Online Health Calculators Can Tell You
Online health calculators provide quick, evidence-based insights into your health status using simple measurements. The most widely used tool is the BMI calculator, which uses your height and weight to determine whether you fall into a healthy weight range according to NHS guidelines. A healthy BMI for most UK adults is between 18.5 and 24.9, though lower thresholds apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage.
- BMI calculators help identify if weight-related health risks may apply to you
- Weight converters allow you to switch between stone, pounds, and kilograms—essential since the NHS uses kg clinically but most UK adults think in stone
- GLP-1 weight loss calculators project potential outcomes with prescription weight management medications like Mounjaro and Wegovy
- Progress trackers help you log and monitor weight changes over time
These tools are informational only and do not replace advice from your GP. Use them to start conversations about your health, not as diagnostic tools.
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 Online Calculators Safely — NHS Context
The NHS recommends using online health calculators as part of a broader approach to understanding your weight and health. Our free BMI calculator and weight converter are designed to align with current NHS health thresholds, making them practical for UK health planning.
Important considerations: online calculators cannot assess your individual health, account for muscle mass versus fat, or consider medical conditions you may have. A BMI in the overweight or obese range does not automatically mean you need treatment—your GP will assess your overall health picture, including waist measurement, blood pressure, and other factors. If you're considering prescription weight management options, a licensed prescriber will conduct a full clinical assessment before any prescription is issued.
Use our online tools to gather information, track progress, and prepare informed questions for your GP.
- 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 online health calculators accurate?
Online calculators like BMI tools are accurate for their intended purpose—providing a screening measurement. However, they have limitations. BMI doesn't distinguish between muscle and fat, doesn't account for where fat is stored, and may be less accurate in elderly people or very muscular individuals. Use them as a starting point, not a diagnosis. Your GP can provide personalised assessment.
What's the difference between NHS health guidance and other online calculators?
MyWeightCheck calculators are aligned with NHS health thresholds, including ethnicity-adjusted BMI ranges for South Asian and Black African backgrounds. The NHS recommends a healthy BMI of 18.5–24.9 for most adults, but lower thresholds (18.5–22.9) for certain ethnic groups who face higher health risks at lower BMI. Always check that any online tool uses current NHS guidance.
Can I use an online weight loss calculator to estimate results with Mounjaro or Wegovy?
Yes. Our GLP-1 weight loss calculator helps you estimate potential weight loss outcomes based on clinical trial data from medications like Mounjaro (tirzepatide) and Wegovy (semaglutide). However, individual results vary significantly. Clinical trials show average weight loss of 15–21% with Mounjaro and approximately 15% with Wegovy, but your personal outcome depends on many factors including adherence, lifestyle changes, and individual response.
Should I rely on an online calculator instead of seeing my GP?
No. Online calculators are informational tools only. If you have concerns about your weight, health, or are considering prescription weight management medication, consult your GP. They can assess your full health picture, discuss your individual risk factors, and refer you to appropriate services. Prescription medications like Mounjaro and Wegovy require a clinical assessment and prescription from a licensed healthcare professional.
How often should I use an online progress tracker?
Weekly tracking is typical for weight management. Weigh yourself at the same time of day, preferably in the morning before eating. Weight fluctuates naturally due to water retention, hormones, and digestion, so focus on trends over weeks rather than daily changes. If you're using prescription weight loss medication, your prescriber may recommend specific tracking frequency during dose adjustments.
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.