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
Understanding the Weight Mass Equation in UK Health
The weight mass equation is a fundamental concept in health and fitness that helps you understand the relationship between your body weight and overall health. In the UK, we use weight in kilograms, stone, and pounds to measure body mass, and this measurement is crucial for calculating your BMI and assessing whether you're at a healthy weight according to NHS guidance. Understanding how weight relates to your health can help you make informed decisions about your wellbeing.
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 Weight Mass Works in UK Health Assessment
In UK health guidance, weight is measured in kilograms (kg), stone, or pounds (lbs), and it forms the basis of several important health calculations. The weight mass equation is essentially the principle that your body weight, combined with your height, determines your BMI (Body Mass Index) — the NHS's primary screening tool for healthy weight assessment. The equation is straightforward: BMI = weight (kg) ÷ height (m)². According to NHS guidance, a healthy BMI for most UK adults falls between 18.5 and 24.9, though for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the threshold is lower (18.5 to 22.9). Weight management is about understanding this relationship and using tools like our free BMI calculator above to assess where you sit on the healthy weight spectrum. Your weight alone doesn't tell the full story — it's the combination of weight and height that matters for health screening. If you're concerned about your weight or want personalised advice, your GP can assess your individual circumstances and recommend appropriate health guidance based on NHS standards.
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 Measurements for UK Health Guidance
In the UK, we convert weight between metric (kilograms) and imperial (stone and pounds) measurements regularly, so understanding both systems is important. A healthy weight range depends on your height — for example, for someone who is 5ft 8in (173cm) tall, the healthy weight range is approximately 55kg to 74kg (8st 9lbs to 11st 9lbs). You can instantly convert between units and check your personal healthy weight range using our free weight converter and BMI calculator on this page. Weight management forms part of broader health management, and the NHS encourages a holistic approach including balanced nutrition, regular physical activity, and adequate sleep. If your weight falls outside the healthy range, your GP can discuss personalised strategies with you, which may include referral to weight management support services, lifestyle advice, or in some cases, prescription weight management options alongside lifestyle changes. Remember that sustainable weight management typically involves losing no more than 0.5–1kg per week.
- 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 the weight mass equation?
The weight mass equation is the formula used to calculate BMI: weight (kg) ÷ height (m)². This combines your weight with your height to determine whether you fall within the NHS healthy weight range (18.5–24.9 BMI). It's a key health screening tool used across UK healthcare, though it has limitations — it doesn't distinguish muscle from fat.
How do I convert my weight for UK health assessment?
Use our free weight converter to switch between kg, stone, and pounds. For example, 70kg equals 11 stone 0.1lbs. Then use the BMI calculator with your height to see where you fall on the NHS healthy weight scale. This helps you understand your weight in the context of UK health guidance.
What is a healthy weight in the UK according to NHS guidance?
A healthy BMI is 18.5–24.9 for most UK adults. For those of South Asian, Chinese, Black African, or Black Caribbean heritage, it's 18.5–22.9. Your specific healthy weight depends on your height. Use our free BMI calculator to find your personal healthy weight range based on your measurements.
Why is weight important in UK health management?
Weight combined with height determines your BMI, which is the NHS's primary screening tool for assessing health risk. Excess weight increases the risk of type 2 diabetes, heart disease, and other conditions. Even a 5–10% reduction in body weight can have significant health benefits according to NHS guidance.
Should I be concerned about my weight if my BMI is high?
If your BMI is above 25, it's worth discussing with your GP. They can assess your individual health, consider other factors like waist circumference and family history, and recommend personalised support. NHS weight management services are available through your GP, and in some cases, prescription weight management options may be appropriate.
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.