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 Percentage Calculator — UK Health Guide
A weight percentage calculator helps you track how much of your body weight you've lost, which is often more meaningful than just the number of kilograms. In UK weight management and NHS health guidance, understanding your progress as a percentage can motivate sustainable changes and help you monitor whether your weight management approach is working. This guide explains how to calculate weight percentage loss, why it matters for your health, and how it relates to your overall fitness and wellbeing goals.
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 Your Weight Loss Percentage
To calculate your weight loss as a percentage, use this formula: (Starting weight − Current weight) ÷ Starting weight × 100 = Percentage lost. For example, if you started at 100kg and now weigh 90kg, you've lost 10% of your body weight.
Weight percentage is particularly useful because it shows progress relative to your starting point. Losing 10% of body weight has clinically meaningful benefits for health — even if the absolute kilogrammes seem modest. The NHS emphasises that a 5–10% reduction in body weight can improve blood pressure, blood sugar control, and reduce joint strain, regardless of whether you reach a "target weight".
- 5% loss = noticeable health improvements
- 10% loss = significant cardiovascular benefits
- 15% loss = substantial risk reduction for type 2 diabetes
Use our free BMI calculator alongside this calculation to see how your percentage loss affects your BMI category, as both metrics together give you a complete picture of your weight management progress.
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.
UK Weight Management Standards and NHS Guidance
The NHS recommends losing weight at a rate of 0.5–1kg per week for sustainable, healthy weight loss. This typically equates to losing 2–4% of your body weight per month. Rapid percentage loss (more than 2kg per week) can result in muscle loss and is not recommended without medical supervision.
In UK clinical practice, weight loss medications like GLP-1 injections are assessed based on percentage weight loss achieved in trials. For instance, clinical trials showed Mounjaro helped participants lose an average of 15–21% of body weight, whilst Wegovy supported approximately 15% loss on average — though individual results vary significantly. Your GP can advise whether monitoring your percentage loss is relevant to your personal health goals and any weight management treatment you may be considering.
Track your weight percentage progress using our free progress tracker, which automatically calculates both absolute weight lost and your percentage loss over time. This tool helps you visualise your journey month by month, making it easier to spot trends and stay motivated through plateaus.
Combine percentage tracking with our free weight converter and BMI calculator to get a holistic view of your health. Set realistic percentage goals — aiming for 5–10% loss as an initial target is evidence-based and achievable. If you're considering weight management support, your GP can help you understand what percentage loss is realistic for you based on your individual circumstances and any medical conditions.
- 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 is a healthy weight percentage loss per week?
The NHS recommends losing 0.5–1kg per week, which typically equals 1–2% of body weight per month. Faster loss is not recommended as it often results in muscle loss rather than fat loss. Sustainable weight management focuses on steady, consistent progress rather than rapid drops.
Why is weight percentage better than just tracking kilograms?
Percentage loss shows your progress relative to your starting point, making it comparable across individuals of different sizes. A 10kg loss means different things for someone starting at 70kg versus 150kg. Percentage loss also correlates more directly with health improvements recognised by the NHS.
Does clinically studied weight loss really make a health difference?
Yes — the NHS confirms that losing just 5–10% of body weight improves blood pressure, blood sugar control, reduces cardiovascular risk, and eases joint pain. These benefits occur independent of reaching a specific "target weight", making percentage-based goals meaningful for health outcomes.
Can I calculate weight percentage loss if I'm using GLP-1 medication?
Yes, percentage loss is actually how clinical trials measure GLP-1 medication effectiveness. Mounjaro and Wegovy trials reported average losses of 15–21% and 15% respectively, though individual results vary. Tracking your percentage helps you see if your progress matches realistic expectations.
How do I use the weight percentage calculator with my BMI?
Use our free BMI calculator and weight converter together with percentage loss tracking. As your percentage loss increases, your BMI should move towards the healthy range (18.5–24.9 for most adults, lower for South Asian and Black African/Caribbean adults). This combined approach gives you a complete health picture.
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.