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 Weight Management
Health calculators are essential tools for understanding your current weight status and planning sustainable weight loss. Whether you're checking your BMI, converting between stone and kilograms, or exploring weight loss medication options, using the right calculator helps you make informed decisions about your health. MyWeightCheck provides free UK-aligned health calculators that work with NHS guidelines and UK measurements, making it easier to track your wellness journey and discuss results with your GP.
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.
Types of Health Calculators Available
Several key calculators help with weight management in the UK context. Your BMI calculator determines whether your current weight falls within the NHS healthy weight range (18.5–24.9), overweight (25.0–29.9), or obese (30.0+) categories. For those of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply, making personalised assessment crucial. A weight converter switches between kilograms, stone, and pounds — essential since UK adults typically use stone and pounds while clinical measurements use kilograms. Our GLP-1 weight loss calculator projects potential weight loss if you're considering prescription medications like Mounjaro or Wegovy, based on clinical trial data. These tools work together: calculate your current BMI using our free BMI calculator above, convert your weight to your preferred unit with the weight converter, and if eligible, explore projected outcomes with the GLP-1 calculator to understand realistic expectations.
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.
How to Use Health Calculators Effectively
Start by gathering accurate measurements: your current weight (in any unit — the weight converter handles this), height in centimetres or feet and inches, and age if required. Enter these into the relevant calculator to get gradual improvement. Write down your results and discuss them with your GP, especially if your BMI suggests overweight or obesity, or if you're interested in weight loss medication. Results from health calculators are screening tools, not diagnoses — your GP can provide personalised advice based on your complete health picture. Use the progress tracker alongside calculators to monitor changes over weeks and months, which often shows progress that scales alone might miss. Remember that even modest weight loss (5–10% of body weight) delivers meaningful health benefits like improved blood pressure and better blood sugar control.
- 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.
Why do UK health calculators use different units than other countries?
The UK traditionally measures body weight in stone and pounds, while clinical systems use kilograms. Most health calculators offer all three units because GPs and NHS resources work in kilograms, but patients prefer stone. This dual approach ensures you understand your results in familiar terms and can discuss them clearly with your healthcare provider using the same measurements your GP uses.
Is a BMI calculator accurate for everyone?
BMI is a useful screening tool but has limitations. It doesn't distinguish between muscle and fat — athletes may have high BMI but low body fat. BMI is also less accurate for elderly adults, during pregnancy, or for very tall or very short individuals. Always discuss your personal BMI with your GP, especially if you're muscular or have health concerns, as waist circumference and overall health matter too.
What's the difference between Mounjaro and Wegovy calculators?
Both are GLP-1-based medications licensed for weight management in the UK, but they work slightly differently. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials show both may help with weight loss — Mounjaro averaged 15–clinically studied weight loss, Wegovy around 15%. A calculator based on your weight and dose can project realistic outcomes, though individual results vary considerably.
Can I use a health calculator to diagnose obesity?
No — calculators are screening tools only, not diagnostic instruments. A BMI calculator shows your BMI category according to NHS guidelines, but diagnosis requires assessment by a healthcare professional. Your GP can evaluate your complete health picture, family history, and any weight-related conditions to determine whether treatment is appropriate for you.
Should I use a health calculator before speaking to my GP about weight loss?
Absolutely. Calculating your BMI, noting your current weight in kilograms and stone, and understanding your healthy weight range beforehand gives you concrete information to discuss with your GP. This makes your appointment more productive — you can ask specific questions about whether prescription weight loss treatment like Mounjaro or Wegovy might be suitable, based on your BMI and health conditions, rather than starting from scratch.
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.