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
Weight Calc — Understanding Your Health Numbers in the UK
A weight calc is any tool or calculation that helps you understand your body weight in the context of your health. In the UK, the most important health measurements are your BMI (body mass index), your weight in stone and kilograms, and your waist circumference. This guide explains what these numbers mean, how to use them, and where to find reliable NHS guidance. MyWeightCheck provides free calculators to help you measure and track these health markers.
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 UK Weight Calculators Work
A weight calc typically combines your weight and height to calculate your BMI, which the NHS uses as a screening tool for health risk. The standard BMI formula is weight (kg) divided by height (m) squared. For UK adults, the NHS categorises BMI as follows: underweight below 18.5, healthy weight 18.5–24.9, overweight 25.0–29.9, obese 30.0–34.9, and severely obese above 40.0.
However, BMI has limitations — it doesn't distinguish between muscle and fat, and ethnicity affects health risk at the same BMI. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds: healthy weight is 18.5–22.9, and overweight begins at 23.0.
- BMI is a useful screening tool but not a complete picture of health
- Waist circumference is equally important — over 94cm for men and 80cm for women indicates increased risk
- Weight management and healthy weight uk guidance emphasise sustainable lifestyle change alongside any calculation
Use our free BMI calculator above to check your personal BMI instantly and see where you fall within NHS categories.
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 Weight Calc for Health Management
Beyond simple calculations, weight management in the UK involves understanding your individual health context. Your GP can assess whether your weight poses health risks based on your BMI, waist measurement, and any weight-related conditions you may have — such as type 2 diabetes, high blood pressure, or sleep apnoea.
Our weight converter tool lets you switch between kilograms, stone, and pounds instantly, and our progress tracker allows you to log changes over time. If you're exploring weight loss options, our GLP-1 weight loss calculator can help you understand how prescription weight management medication might work alongside lifestyle changes. Always consult your GP for personalised nhs health advice about your weight and any health concerns.
- 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's the difference between BMI and healthy weight?
BMI is a screening tool based on height and weight ratio. Healthy weight is the range of weight that statistically reduces health risks for your height — typically a BMI of 18.5–24.9 for most UK adults, lower for some ethnic groups. Your GP can discuss what's healthy for you personally.
Why do UK health measurements use stone and kilograms?
The NHS primarily uses kilograms for clinical records, but UK adults commonly use stone and pounds for personal measurement. MyWeightCheck provides conversions between all three systems so you can use whichever feels natural to you.
Can I use a weight calc to diagnose a health problem?
No. Weight calculators are screening tools only. They show whether your weight falls in a range associated with health risk, but only your GP can diagnose health conditions or recommend treatment. Always discuss results with your healthcare professional.
What's the most accurate weight calc method?
BMI remains the NHS standard, but waist circumference and body composition are also important. No single calculation is perfect — that's why your GP considers your overall health picture, not just one number.
How often should I use a weight calc to track my health?
Monthly checks are reasonable for weight tracking. However, obsessive daily weighing isn't helpful — weight naturally fluctuates. Our free progress tracker helps you see trends over weeks and months without getting caught up in daily variations.
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.