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
Calculate Your Optimal Weight Using NHS Guidelines
Your optimal weight depends on your height, age, and overall health rather than a single target number. The NHS provides evidence-based healthy weight ranges using BMI (body mass index) as the primary screening tool. For most UK adults, a healthy BMI falls between 18.5 and 24.9, though ethnicity-adjusted thresholds apply for South Asian, Chinese, Black African, and Black Caribbean backgrounds. Use our free BMI calculator to find your personal healthy weight range instantly, and discover how weight management approaches can support your long-term health 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.
Finding Your Healthy Weight Range
Your optimal weight is not about reaching a single number—it's about finding a range that supports your individual health. The NHS uses BMI (weight in kg divided by height in metres squared) as a practical screening tool for healthy weight.
- Healthy BMI range: 18.5–24.9 for most UK adults
- South Asian, Chinese, Black African, or Black Caribbean adults: 18.5–22.9 (lower thresholds due to higher health risks at equivalent BMI)
- Overweight range: BMI 25–29.9
- Obese range: BMI 30 and above
To calculate your personal healthy weight range, use our free BMI calculator above. For a 1.73m tall adult (5ft 8in), the healthy weight range is approximately 55–74 kg (8st 10lbs to 11st 9lbs). However, BMI has limitations—it doesn't distinguish between muscle and fat, so athletes may have a higher BMI with low body fat. Your GP can provide personalised guidance based on your individual health picture.
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.
Moving Towards Your Optimal Weight
If your current weight is above the healthy range, the NHS recommends gradual, sustainable weight loss of 0.5–1 kg per week. This typically requires a calorie deficit of around 500 kcal per day, achieved through balanced eating and increased physical activity. Weight management approaches vary—some people benefit from structured diet plans, others from lifestyle changes alone, and some from prescription support alongside behaviour change.
For adults with a BMI of 30 or above (or 27+ with weight-related health conditions such as type 2 diabetes or high blood pressure), prescription weight loss medications may be considered through NHS specialist services or private assessment. Track your progress using our free progress tracker, and use the weight converter to switch easily between stone, pounds, and kilograms as you work towards your goal.
- 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 optimal weight range?
Multiply your height in metres by itself, then divide your weight in kg by that number to get your BMI. A healthy BMI is 18.5–24.9 for most UK adults. Multiply your BMI target (e.g. 24.9) by your height squared to find your maximum healthy weight. Use our free BMI calculator to do this instantly.
Is there one "perfect" weight for me?
No—optimal weight is a range, not a single number. It varies based on muscle mass, bone density, age, and individual health factors. Even within a healthy BMI range, what's optimal for you depends on your fitness level and any health conditions. Your GP can help identify your personal target range.
Why are BMI thresholds different for some ethnic groups?
Research shows South Asian, Chinese, Black African, and Black Caribbean adults face higher health risks at lower BMI levels. The NHS recommends these groups use a healthy BMI range of 18.5–22.9 instead of 18.5–24.9 to better reflect their individual cardiovascular and diabetes risk.
How quickly should I aim to reach my optimal weight?
The NHS recommends losing no more than 0.5–1 kg per week for sustainable results. Faster weight loss can lead to muscle loss and nutritional deficiencies. A calorie deficit of around 500 kcal per day typically supports 0.5 kg weekly loss. Weight management should combine dietary changes with increased physical activity.
Can medication help me reach my optimal weight?
For eligible adults, prescription weight loss medications may support sustainable results alongside lifestyle changes. These are available through NHS specialist services or private assessment for those with a BMI of 30+ (or 27+ with health conditions). Any medication requires a prescription from a licensed prescriber and ongoing health monitoring.
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.