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
How To Calculate A Weight — And What It Means For Your Health
Calculating your weight is straightforward, but understanding what that number means for your health is what really matters. Whether you're tracking progress, checking your BMI, or exploring weight management options, knowing how to measure and interpret your weight is the first step. We'll walk you through the practical methods, UK measurements, and NHS health guidance to help you make sense of the numbers.
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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.
Methods For Measuring And Recording Your Weight
Weighing yourself accurately is the foundation of any health assessment. Use a digital bathroom scale on a flat, hard surface—avoid carpeted areas which give inconsistent readings. Weigh yourself at the same time each day, preferably in the morning before eating or drinking, as this eliminates daily fluctuations from food and water intake. Wear minimal clothing or no clothing for accuracy, and note that weight naturally varies by 1–2 kg throughout the day depending on hydration, meals, and exercise.
- Record your weight in kg for clinical accuracy, though UK adults often prefer stone and pounds
- Use our free weight converter to switch between kg, stone, and lbs instantly
- Take weekly averages rather than daily readings to see true progress
- Track trends over 2–4 weeks rather than focusing on single measurements
For weight management purposes, consistency matters more than precision. If you're exploring prescription weight loss options like Mounjaro or Wegovy, your healthcare provider will need accurate baseline measurements, so establishing a reliable weighing routine is essential.
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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.
Understanding Your Weight In Context — BMI And Health
Your weight alone doesn't tell the full health story. The NHS uses BMI (body mass index) to assess whether your weight is healthy for your height. BMI = weight (kg) ÷ height (m)². A healthy BMI range is 18.5–24.9 for most UK adults, though lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage (18.5–22.9).
- Calculate your BMI instantly using our free BMI calculator on this page
- A BMI of 30 or above, or 27–29.9 with weight-related health conditions, may qualify you for prescription weight management support
- Remember: BMI doesn't distinguish muscle from fat—waist measurement and overall fitness matter too
Once you know your weight and BMI, your GP can provide personalised advice about whether interventions suit your individual health picture.
- 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 best time of day to weigh yourself?
Weigh yourself each morning before eating, drinking, or exercising, after using the toilet. This gives the most consistent and accurate reading. Avoid weighing at night or after meals, as weight naturally increases during the day due to food and fluid intake. Consistency matters more than the exact time—pick one time and stick with it daily.
Should I record my weight in kg or stone?
Record in kg for clinical accuracy and healthcare provider discussions—the NHS uses kg. However, convert to stone and lbs using our free weight converter if you prefer imperial measurements or find them more relatable. Many UK adults use both: kg for health assessments, stone for personal tracking.
How often should I weigh myself when losing weight?
Once weekly is ideal for most people. Daily weighting creates anxiety and obscures real progress, as weight fluctuates 1–2 kg naturally due to hydration and food intake. Weekly weighing, recorded on a progress tracker, shows genuine trends over 2–4 weeks and is much more motivating and accurate.
What does my weight calculation mean for weight management?
Your weight combined with height determines your BMI, which indicates whether you qualify for prescription weight management support like Mounjaro or Wegovy. Try our free GLP-1 weight loss calculator to explore potential outcomes. Always discuss your weight and health options with your GP first.
Why does the NHS focus on BMI rather than just weight?
BMI accounts for height, giving context to your weight. Two people weighing 80kg may have completely different health risks depending on their height. BMI is a screening tool—it's not perfect (doesn't account for muscle), but it's a practical starting point for NHS health guidance and treatment eligibility assessment.
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.