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 Much Weight Have I Lost Calculator — UK Guide
Tracking weight loss is essential to staying motivated and understanding your progress. Whether you're measuring in stone, pounds, or kilograms, knowing exactly how much weight you've lost helps you see real results and adjust your approach if needed. Our free weight loss calculator uses NHS-aligned healthy weight ranges and BMI standards to give you personalised context about your progress. Simply enter your starting weight and current weight in your preferred units — stone, pounds, or kilograms — and the calculator shows you your total loss, percentage of body weight lost, and how your BMI has changed. This gives you a complete picture of your health journey, not just a number on the scales.
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 Your Weight Loss Results
Our free weight loss calculator does more than just subtract numbers — it shows you how your weight loss translates to real health improvements. When you enter your starting weight and current weight, the calculator instantly displays your total loss in kilograms, stones, and pounds, making it easy to track progress in the units you prefer. It also calculates your percentage of body weight lost, which is a more meaningful measure than absolute numbers — for example, losing 5kg means something different for a person who started at 80kg versus 120kg.
The calculator then compares your starting BMI and current BMI against NHS healthy weight categories. This shows you whether you've moved from overweight into the healthy range, or how much further you need to progress. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the calculator applies the lower NHS thresholds (healthy BMI 18.5–22.9), recognising that these groups face higher health risks at standard BMI levels.
Use our free BMI calculator above alongside this progress tracker to understand your personal healthy weight range and see exactly where you stand today.
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.
What to Do With Your Results
If your calculator shows you're now in the healthy weight range (BMI 18.5–24.9), that's excellent — even if you haven't reached a "goal" number. Research shows that losing just 5–10% of your body weight brings significant health benefits: lower blood pressure, improved blood sugar control, reduced joint pain, and better sleep quality.
If your results show you're still above the healthy weight range, remember that progress isn't always linear. Weight fluctuates daily due to water retention, hormones, and digestion. Use our free progress tracker to log weekly or monthly measurements rather than obsessing over daily changes. This helps you spot real trends beneath the daily noise.
If you'd like support reaching your ideal weight for your height, your GP can discuss options including structured diet programmes, increased physical activity, or prescription weight loss medication — always tailored to 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.
How do I calculate my weight loss in stone and kilograms?
Enter your starting weight and current weight using the calculator above — you can input in kilograms, stone, or pounds. The calculator instantly converts between all units and shows your total loss, percentage lost, and BMI change. This gives you a complete picture across all common UK measurements.
Is my weight loss amount good progress?
The NHS recommends losing 0.5–1 kg (1–2 lbs) per week as sustainable and healthy. Total progress depends on your timeframe — losing 5kg over 10 weeks is excellent, whereas 5kg over 2 weeks may indicate very rapid loss requiring medical support. Use the percentage of body weight lost as a key indicator; 5–10% loss brings measurable health benefits.
What is a healthy weight for my height?
A healthy weight varies by height, age, sex, and muscle mass. The NHS healthy weight range is a BMI of 18.5–24.9. Use our free BMI calculator to enter your height and current weight — it instantly shows your healthy weight range for your height. For adults from certain ethnic backgrounds, lower thresholds apply.
Why does my weight fluctuate even though I'm losing fat?
Daily weight changes are often water retention, hormones, digestion, or sodium intake — not fat loss. Real fat loss is gradual. Tracking weekly or monthly averages using our free progress tracker is far more meaningful than daily weighing. You'll see the true downward trend over time, even if daily numbers bounce around.
Should I aim for a specific number on the scales?
Rather than a single number, aim for a healthy BMI range (18.5–24.9) and how you feel — energy levels, fitness, sleep quality, and clothes fit matter too. Your GP can advise on a healthy weight range for you personally, considering your height, build, and any health conditions. Weight is just one measure of health.
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.