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
Calculator for Mass — Convert Weight and Check Your BMI
A calculator for mass helps you understand your weight in different units and how it relates to your health. In the UK, we use kilograms, stone, and pounds to measure body weight — and converting between them is the first step towards understanding your healthy weight range. Whether you're tracking your progress, preparing for a health appointment with your GP, or simply curious about what your weight means according to NHS guidance, the right tools make all the difference. Our free calculators let you convert your mass instantly and see where you fall on the healthy weight scale.
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.
Understanding Mass, Weight, and Your Health
Mass and weight are related but different: Mass is the amount of matter in your body (measured in kilograms or pounds), whilst weight technically refers to the force of gravity acting on that mass. In everyday UK health contexts, we use "weight" and "mass" interchangeably to mean the same thing.
- Kilograms (kg): The metric standard used by NHS clinicians and most of the world
- Stone and pounds: The traditional UK unit — 1 stone equals 14 pounds exactly, and 1 stone equals 6.35 kg
- Pounds (lbs): Used individually, especially in US contexts, but less common in UK health
A calculator for mass lets you convert between these units instantly. More importantly, once you know your weight in kg, you can use our free BMI calculator on this page to check where your mass falls on the NHS healthy weight scale — whether that's underweight, healthy weight, overweight, or obese. This is the foundation of understanding your personal health baseline.
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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.
Why Measuring Your Mass Matters for Your Health
Your mass alone doesn't tell the full health story, but it's an essential starting point. The NHS uses body mass index (BMI) — your weight in relation to your height — to assess health risk. A healthy BMI for most UK adults is between 18.5 and 24.9. If you're overweight (BMI 25–29.9) or obese (BMI 30 and above), your risk of type 2 diabetes, heart disease, and certain cancers increases significantly.
The good news: even a 5–10% reduction in your mass can improve blood pressure, blood sugar control, and overall wellbeing. Use the weight converter and BMI calculator above to understand your current mass and healthy weight range. If you have health concerns, your GP can offer personalised guidance based on your individual circumstances.
- 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 mass and weight?
In physics, mass measures the amount of matter in your body, whilst weight measures the gravitational force acting on that mass. In UK health contexts, we use these terms interchangeably. Your mass in kilograms or stone is what your GP and NHS services use to assess your health.
How do I convert my mass from kilograms to stone?
Divide kilograms by 6.35029 to get stone. For example, 70 kg ÷ 6.35 = 11.02 stone (approximately 11 stone 0 pounds). Use our free weight converter on this page for instant conversion between kg, stone, and pounds.
What is a healthy mass according to the NHS?
A healthy mass depends on your height. The NHS recommends a BMI between 18.5 and 24.9 for most UK adults. Use our free BMI calculator above to find your healthy weight range. For South Asian, Chinese, Black African, and Black Caribbean adults, lower thresholds apply (BMI 18.5–22.9).
How does my mass affect my health?
Your mass relative to your height (BMI) indicates health risk. Being overweight or obese increases risk of type 2 diabetes, heart disease, and other conditions. However, even a 5–10% reduction in mass can significantly improve health markers like blood pressure and blood sugar control.
Can a mass calculator help me with weight loss?
Yes. A mass/weight calculator helps you track your progress and understand your starting point. If you're considering weight loss treatment, our free GLP-1 weight loss calculator can show you potential outcomes. Always discuss any weight management plan with your GP first.
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.