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 Difference Calculator — UK Health Guide
A weight difference calculator helps you track how much weight you've lost or gained over a specific period. Whether you're monitoring your progress towards a healthier weight, recovering from illness, or managing weight for health reasons, understanding the numerical change is the first step. Our free calculator lets you compare your weight across different units—stone, kilograms, and pounds—making it easy to see your progress in the measurements you prefer. This simple tool supports your weight management goals with NHS-aligned health guidance.
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 Use a Weight Difference Calculator for UK Weight Management
A weight difference calculator works by comparing two weight measurements taken at different times. Simply enter your starting weight and current weight, select your preferred units (stone and pounds, kilograms, or pounds), and the calculator instantly shows the difference. Most UK adults find it helpful to track progress weekly or monthly rather than daily, as weight naturally fluctuates due to hydration, food intake, and hormones.
- Starting weight: Your weight at the beginning of your tracking period
- Current weight: Your weight on today's date
- Time period: Note how many weeks or months have passed—this helps you understand your rate of weight loss or gain
- Unit preference: Use stone for familiar UK measurements, kg for clinical context, or lbs for detailed tracking
The NHS recommends tracking weight progress at a sustainable rate of 0.5 to 1 kg (approximately 1 to 2 lbs) per week. Use our free weight converter and BMI calculator together with this tool to understand not just the number that's changed, but what that means for your healthy weight uk range and overall health context.
Clinically BackedWeight Loss
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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 Difference Tracking Matters for Your Health
Monitoring weight change is valuable for understanding your health trajectory and the effectiveness of any lifestyle changes. Even modest weight loss—as little as 5 to 10 per cent of your body weight—can bring measurable health benefits including lower blood pressure, improved blood sugar control, and reduced joint strain. Tracking regularly builds motivation and helps you spot patterns.
Our free progress tracker allows you to log multiple measurements over time, creating a visual record of your weight management journey. If you're using prescription weight loss medication or following an NHS weight loss programme, tracking becomes even more important for demonstrating progress to your GP and staying motivated. For personalised advice about what weight loss target is right for you, always consult your GP or a health professional.
- 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 tracking weight in stone versus kilograms?
Stone and pounds are traditional UK measurements—most UK adults use them for body weight. Kilograms are the clinical standard used by the NHS and healthcare professionals. Both are equally valid; choose whichever feels more meaningful to you. Use our weight converter to switch between units instantly.
How often should I weigh myself when using a weight difference calculator?
The NHS suggests weighing yourself once a week, ideally at the same time of day and in similar clothing. Daily weighing can be discouraging because natural water retention, food, and hormonal changes cause daily fluctuations. Weekly tracking gives a clearer picture of genuine progress.
Is losing weight quickly better if I'm using a weight difference calculator to track it?
No. gradual weight management (more than 1 to 2 lbs per week) is not recommended without medical supervision and often leads to muscle loss, nutrient deficiencies, and unsustainable habits. The NHS recommends gradual, steady loss alongside dietary changes and increased physical activity.
Can I use a weight difference calculator if I'm on weight loss medication like Mounjaro or Wegovy?
Yes, absolutely. Tracking with a calculator is very helpful if you're using GLP-1 medication. Our GLP-1 weight loss calculator can help you project expected loss at different doses, and your weight difference tracker records your actual progress against those projections.
What should I do with my weight difference measurements—should I share them with my GP?
Yes. If you're working towards a healthier weight or managing a weight-related health condition, sharing progress with your GP is valuable. Bring your tracked measurements to appointments; they help your GP understand your commitment and adjust any lifestyle advice or treatment if needed.
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.