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
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Weight Loss Clothing Size Calculator — How Weight Loss Changes Your Fit
As you lose weight through diet, exercise, or prescription weight loss medication, your clothing sizes will gradually change. Understanding how weight loss translates to dress size reductions can help you track progress beyond the scales and stay motivated throughout your weight management journey. This guide explains the relationship between weight loss and clothing sizes in the UK context.
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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.
How Weight Loss Affects Clothing Sizes
Weight loss typically results in visible clothing size changes after losing approximately 5–10% of your body weight, though this varies by individual, body shape, and where fat is lost. In the UK, dress sizes generally decrease by one size for every 6–10kg of weight loss, though this is approximate and depends on your starting size and body composition.
- 5–10kg loss: Often visible in how clothes fit, but may not change formal dress sizes
- 10–15kg loss: Usually results in dropping one UK dress size
- 15–20kg loss: Typically drops one to two sizes
- 20kg+ loss: May drop two or more sizes depending on distribution
Use our free BMI calculator to understand your weight loss target, and track progress with our weight loss progress tracker to monitor both weight and clothing fit changes over time. Men's clothing sizes (chest and waist measurements) typically shift by one size for every 5–8kg of weight loss.
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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.
Weight Loss and Body Composition — Why Size Matters Beyond Weight
Two people losing the same amount of weight may experience different clothing size changes because weight loss isn't uniform across your body. Fat loss from the face, arms, or torso becomes visible in clothing fit before you see the same change on a scale. If you're combining weight loss with strength training or physical activity, muscle gain can offset some weight loss on the scales, but clothing fit may still improve significantly.
For those using prescription weight loss medication like GLP-1 weight loss injections, tracking clothing fit alongside your BMI using our free BMI calculator provides valuable motivation. Converting your weight using our weight converter between kg, stone, and lbs helps you understand your progress in whatever units feel most meaningful to you.
- 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 many kilograms of weight loss equals one UK dress size?
On average, dropping one UK women's dress size requires losing approximately 6–10kg, though this varies by body shape and where fat is lost first. Men's clothing sizes typically change by one size for every 5–8kg of weight loss. Individual variation is significant—tracking both your weight and how clothes fit gives the clearest picture of progress.
Can I lose weight but stay the same clothing size?
Yes. In the early stages of weight loss (first 5kg or so), clothes may fit slightly better without changing size. Additionally, if you're building muscle through exercise while losing fat, your weight may decrease less than expected, but clothing fit often improves noticeably. This is why tracking both scales and fit is valuable.
How long does it take to drop a clothing size?
At a healthy rate of losing 0.5–1kg per week, you might expect to drop a dress size in approximately 6–10 weeks. However, this depends on your starting size, body composition, and where your body loses fat first. Faster weight loss with prescription medication like Mounjaro or Wegovy may accelerate visible size changes, though individual results vary.
Does weight loss happen evenly across your body?
No. Weight loss typically follows a genetically determined pattern—many people lose from the face and upper body first, with lower body fat being last to shift. This is why you might notice clothes fitting differently in some areas before others. Tracking progress across different measurements (waist, hips, chest) alongside weight gives a fuller picture.
What's the best way to track clothing size changes while losing weight?
Keep a note of your current sizes across different shops (sizes vary between brands), and check fit every 2–4 weeks. Use our free progress tracker to record weight alongside clothing fit changes. Our BMI calculator and weight converter help you understand your progress in familiar UK measurements, making it easier to stay motivated throughout your weight management journey.
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.