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? — UK Calculator Guide
Your optimum weight is the healthy weight range for your height, calculated using NHS-approved methods. Finding your ideal target weight helps you set realistic health goals and understand what a healthy weight management approach looks like for you. Our guide explains how to calculate your optimum weight using UK measurements, what the NHS recommends, and how different factors affect your personal target range.
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 Optimum Weight in the UK
Your optimum weight depends on three main factors:
- Height — measured in cm or feet and inches
- Age and sex — muscle mass changes with age and differs between men and women
- Body composition — muscle weighs more than fat, so two people at the same weight can look very different
The NHS uses BMI (Body Mass Index) as the primary screening tool for healthy weight. A healthy BMI range is 18.5 to 24.9 for most UK adults. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower range of 18.5 to 22.9 because these groups face higher health risks at the same BMI.
To find your optimum weight range, you can use our free BMI calculator above, which instantly shows you the healthy weight range for your height. You can also use standard formulas like the Devine or Robinson method — these provide an approximate ideal weight based on height, though individual variation is normal.
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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.
Using UK Health Guidance to Set Your Target
The NHS emphasises that one healthy weight doesn't suit everyone. Your optimum weight depends on your genetics, muscle mass, lifestyle, and overall health — not just a number on the scales. Rather than aiming for a single "ideal" weight, health guidance recommends working towards a healthy weight range for your height.
Weight management should be gradual and sustainable. The NHS recommends losing no more than 0.5 to 1 kg per week through a combination of balanced nutrition and physical activity. Use our free weight converter to track your progress in stone and kg, and our progress tracker to log changes over time. If you're concerned about your weight or health, speak with your GP — they can assess your individual situation and refer you to appropriate support.
- 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 optimum weight and ideal weight?
Optimum weight is the healthy range for your height according to health guidelines like BMI. Ideal weight is a specific target based on formulas like Devine or Robinson. In practice, any weight within your healthy BMI range (18.5–24.9) is optimum for you — there's no single "ideal" number that applies to everyone.
How accurate is the BMI calculator for finding optimum weight?
BMI is a useful screening tool and is recommended by the NHS, but it has limitations. It doesn't distinguish between muscle and fat, so very muscular people may have a high BMI despite low body fat. Waist circumference and overall health are also important — speak with your GP for personalised guidance.
Does my optimum weight change as I age?
Yes, metabolism and muscle mass change with age. The healthy BMI range (18.5–24.9) stays the same, but your body composition changes. Older adults may lose muscle naturally, so maintaining strength becomes more important alongside weight management.
Can I use a weight calculator instead of seeing my GP?
Online calculators like MyWeightCheck's BMI calculator are helpful for understanding healthy weight ranges, but they can't replace personal medical advice. Your GP can assess your individual health, medications, and circumstances — always speak with them before starting a weight loss programme.
What should I do if my current weight is well above my optimum range?
Gradual progress is more sustainable than rapid loss. Aim for 0.5–1 kg per week through balanced diet and activity. Your GP can refer you to NHS weight management services (tier 3) or you can access support through community programmes — contact your GP for options in your area.
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.