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
What Is Your Optimum Weight For Height And Age?
Finding your optimum weight depends on your height, age, and overall health rather than a single "perfect" number. The NHS uses BMI (Body Mass Index) as the primary screening tool to determine healthy weight ranges for adults. For most adults, a healthy BMI falls between 18.5 and 24.9, which translates to a specific weight range based on your height. However, age, muscle mass, genetics, and individual health conditions all play a role in what weight is genuinely optimum for you personally. Your GP can provide personalised guidance based on your complete health picture. Try our free BMI calculator above to check where your current weight sits on the NHS scale.
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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.
NHS Healthy Weight Ranges By Height
The NHS doesn't prescribe a single "ideal" weight — instead, it uses BMI ranges to define healthy weight zones for different heights. A healthy BMI of 18.5–24.9 means your weight is in a lower-risk range for chronic diseases like type 2 diabetes and heart disease.
- 5ft 4in (163cm): Healthy weight range approximately 8st 4lbs–11st 1lbs (53–70kg)
- 5ft 6in (168cm): Healthy weight range approximately 8st 12lbs–11st 11lbs (56–75kg)
- 5ft 8in (173cm): Healthy weight range approximately 9st 7lbs–12st 7lbs (60–80kg)
- 5ft 10in (178cm): Healthy weight range approximately 10st 3lbs–13st 5lbs (65–85kg)
These ranges are based on standard adult BMI calculations and apply to men and women. Use our weight converter to calculate your personal healthy weight range, or try our free BMI calculator to check your current BMI instantly.
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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 Age Matters Less Than You Think
Many people assume optimum weight changes significantly with age, but the NHS BMI categories remain the same from age 18 onwards. However, age does affect body composition — as we age, we naturally lose muscle mass and may gain fat, even if the scale doesn't change. This means an older adult and a younger adult with the same BMI may have different actual body fat percentages.
What does change with age is how your body responds to weight gain and the health risks associated with excess weight. An 18-year-old and a 65-year-old with a BMI of 32 both face health risks, but the older adult may experience more immediate joint and cardiovascular strain. Your GP can assess whether your current weight is optimum for your specific age and health profile through a full health check.
- 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.
Does optimum weight change as you get older?
BMI categories stay the same from age 18 onwards, but body composition changes with age — you may lose muscle and gain fat. Your GP can advise on what's optimum for your specific age and health conditions. Health risks from excess weight often increase with age, making weight management increasingly important.
How do I calculate my optimum weight for my height?
Use the NHS BMI formula: your weight in kg divided by your height in metres squared. A healthy BMI is 18.5–24.9. You can use our free BMI calculator above to find your personal healthy weight range instantly based on your exact height.
Is optimum weight different for men and women?
No — the same BMI ranges apply to both men and women. However, women naturally have higher body fat percentages than men (around 25–31% is acceptable for women vs 18–24% for men), so two people with the same BMI may look different. Individual factors matter more than gender.
What if I'm very muscular — does BMI still apply?
BMI doesn't distinguish between muscle and fat, so very muscular individuals may have a high BMI despite low body fat. If you're athletic or strength-train regularly, discuss your personal optimum weight with your GP rather than relying on BMI alone. Waist measurement is also useful.
Can my GP help me find my optimum weight?
Yes — your GP can assess your individual health, medical history, and goals to advise on what weight is optimum for you personally. They may refer you to NHS weight management services if needed. Visit your GP for a health check and personalised guidance on healthy weight management.
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.