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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Find Your Ideal Body Weight
Finding your ideal body weight isn't about chasing a single "perfect" number — it's about reaching a healthy weight range that supports your overall health and wellbeing. The NHS defines healthy weight using BMI (body mass index) alongside other factors like waist circumference and individual health conditions. Your ideal weight depends on your height, age, muscle mass, and personal health goals. This guide explains how UK health services approach ideal weight, how to calculate your own healthy weight range, and why working with your GP is the most effective approach to sustainable weight management.
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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 the NHS Defines Healthy Weight
The NHS uses BMI (body mass index) as the primary screening tool for healthy weight. For most UK adults, a healthy BMI falls between 18.5 and 24.9. However, BMI is not a perfect measure — it doesn't distinguish between muscle and fat, and it doesn't account for where your body stores fat (which matters for health risk).
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds: a healthy BMI starts at 18.5 but only goes up to 22.9. This is because these populations face higher risks of type 2 diabetes and cardiovascular disease at lower BMI levels.
Waist circumference is equally important. The NHS advises:
- Men: under 94cm (37 inches) is ideal; over 102cm (40 inches) indicates high health risk
- Women: under 80cm (31.5 inches) is ideal; over 88cm (34.5 inches) indicates high health risk
Your ideal weight also depends on whether you have weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Use our free BMI calculator to check where you currently stand against these NHS thresholds.
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.
Calculate Your Healthy Weight Range
To find your personal healthy weight range, the formula is simple: multiply your height (in metres, squared) by 18.5 for the lower bound, and by 24.9 for the upper bound. For example, if you're 1.73m tall (5ft 8in), your healthy weight range is approximately 55kg to 74kg (8st 9lbs to 11st 8lbs).
Several other formulas exist for ideal body weight — the Devine and Robinson formulas are widely used — but the NHS BMI range is the most evidence-based starting point for UK health services. Remember that muscle weighs more than fat, so athletes may have a higher "ideal" weight than the BMI range suggests. Your progress tracker can help you monitor changes over time alongside other health markers like energy levels and fitness improvements, not just the scale.
- 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's the difference between ideal weight and healthy weight?
Ideal weight is a personal target within your healthy weight range. Healthy weight is defined by NHS guidelines (BMI 18.5–24.9 for most adults). Your ideal weight depends on your muscle mass, frame size, age, and personal health goals — all factors your GP can help you assess.
Can I use a weight converter to calculate my ideal weight in stone?
Yes. Use our free weight converter to switch between kg, stone, and pounds. Once you know your healthy weight range in kilograms using the BMI formula, convert it to stone and pounds for a measurement that feels more familiar in the UK context.
Should my ideal weight be the same as my partner's if we're the same height?
No. Ideal weight varies based on muscle mass, bone density, frame size, age, and genetics. Two people of identical height can have different healthy weight ranges. This is why BMI is a screening tool, not a diagnosis — your GP provides personalised advice.
What's a realistic timeline to reach my ideal body weight?
The NHS recommends losing 0.5–1kg per week for sustainable results. Reaching your ideal weight safely typically takes months, not weeks. If you're considering prescription weight loss support, discuss timelines and expectations with your GP or a specialist weight management service.
Does my ideal weight change if I have a health condition like type 2 diabetes?
Yes. If you have weight-related health conditions, reaching a lower BMI (or even a 5–10% reduction in current weight) can significantly improve blood sugar control, blood pressure, and cardiovascular health. Your GP can advise on a personalised target weight that best supports your specific conditions.
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.