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 Do You Calculate Your Weight?
Calculating your weight sounds simple—you step on a scale and get a number. But understanding what that weight means for your health is more nuanced. In the UK, we measure body weight in kilograms, stone, and pounds, and that weight sits within health contexts like BMI and healthy weight ranges. This guide explains how weight is calculated, what it tells you about your health, and how to use our free weight converter and BMI calculator to get the full picture of your weight management journey.
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 to Calculate and Understand Your Weight
Your body weight is the total mass of your body measured in kilograms (kg), stone, or pounds (lbs). To measure your weight accurately:
- Use a reliable digital scale on a flat, hard surface
- Weigh yourself at the same time each day—preferably in the morning before eating or drinking
- Wear minimal or consistent clothing to avoid fluctuation
- Measure weekly rather than daily, as weight naturally varies by 1–2 kg due to water retention, digestion, and hormones
In the UK, GPs and NHS health services use kilograms for clinical measurements, but many adults prefer stone and pounds for personal tracking. Our free weight converter on this page lets you switch between kg, stone, and lbs instantly. Once you know your weight, you can calculate your BMI (Body Mass Index) using the simple formula: weight (kg) ÷ height (m)². This gives you context—whether your weight falls in the healthy, overweight, or obese range according to NHS guidelines. Use our free BMI calculator above to find your personal BMI instantly.
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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 Weight Calculation Matters for Health
Knowing your weight is just the starting point. NHS guidance recommends comparing your weight against your height to determine if you're in a healthy range. A healthy BMI is 18.5–24.9, though for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the threshold is lower (18.5–22.9) due to higher health risks at the same weight. Weight alone doesn't tell the full story—your GP considers your waist circumference, fitness level, medical history, and weight-related conditions like high blood pressure or type 2 diabetes. If you're concerned about your weight or considering weight management, your GP can give you personalised NHS health advice tailored to your 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.
How do I calculate my BMI from my weight?
BMI = weight (kg) ÷ height (m)². For example, if you weigh 70kg and are 1.73m tall: 70 ÷ (1.73 × 1.73) = 70 ÷ 2.99 = 23.4 BMI. Use our free BMI calculator on this page to calculate instantly—no a UK pharmacy maths needed.
What's the difference between kg, stone, and pounds?
1 kilogram (kg) = 0.157 stone = 2.2 pounds. In the UK, we often use stone and pounds together (e.g. 11 stone 4 pounds). Our weight converter above lets you switch between all three instantly.
What's a healthy weight for my height in the UK?
A healthy weight range depends on your height and corresponds to a BMI of 18.5–24.9. For example, at 5ft 8in (1.73m), a healthy weight is roughly 55–75kg (8st 9lbs to 11st 10lbs). Your GP can advise your personal healthy range.
Should I weigh myself every day?
Weekly weigh-ins are more reliable than daily—your weight naturally fluctuates 1–2kg daily due to water, food, and hormones. Weigh yourself at the same time each week, preferably in the morning, for the most consistent picture.
What if my weight is in the overweight or obese range?
If your BMI is 25 or above, your GP can discuss your individual health risks and options, which may include lifestyle changes, weight management programmes, or in some cases, prescription support. NHS health advice is always personalised to your circumstances.
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.