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
How To Work Out Your Ideal Body Weight
Your ideal body weight depends on your height, age, sex, and individual health factors — there's no single "perfect" number. The NHS recommends using BMI as a starting point to understand whether your weight is in a healthy range, but ideal weight is personal. This guide explains how to work out what a healthy weight means for you using UK health guidance, formulas, and practical tools to help you find your 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.
Understanding Ideal vs Healthy Weight — NHS Framework
The NHS doesn't specify a single "ideal" weight — instead, it focuses on healthy weight ranges based on your height and BMI category. A healthy BMI is between 18.5 and 24.9 according to UK guidelines.
- Healthy weight range: The weight range where your BMI falls between 18.5–24.9
- Why BMI matters: It's a screening tool that links height to weight and correlates with health risk
- Ethnicity adjustment: For South Asian, Chinese, Black African, or Black Caribbean adults, the healthy BMI range starts at 18.5–22.9 due to higher health risks at lower BMI levels
- Waist measurement: Where you carry weight matters too — the NHS recommends keeping waist circumference below 94cm for men and 80cm for women
Use our free BMI calculator above to find your personal healthy weight range instantly based on your height.
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.
Calculating Ideal Weight Using Formula Methods
Several formulas estimate ideal body weight, though none is universally "correct." The most common UK-used methods are the Devine formula and Robinson formula.
Devine formula: Men: 50kg + 2.3kg per inch over 5 feet; Women: 45.5kg + 2.3kg per inch over 5 feet.
Robinson formula: Men: 52kg + 1.9kg per inch over 5 feet; Women: 49kg + 1.7kg per inch over 5 feet.
These formulas give a starting point, but individual ideal weight varies based on muscle mass, bone density, and frame size. Your GP can help interpret these results in the context of your personal health.
- 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?
Healthy weight refers to a BMI range (18.5–24.9) linked to lower disease risk. Ideal weight is more personal — it's where you feel healthy and energised, which may differ from calculated formulas. Both matter; use healthy weight as a baseline and adjust based on how you feel.
How do I convert my target weight between kg and stone?
Use our free weight converter above to switch between units instantly. As a guide: 1 stone equals 6.35kg. So if your target is 70kg, that's approximately 11 stone. The converter handles the maths for you.
Does my ideal weight change as I age?
BMI categories stay the same, but healthy weight may shift slightly with age due to muscle loss. The NHS BMI ranges apply to all adults, but your GP can advise on realistic targets that account for your age and health conditions.
Should I aim for the lower or upper end of the healthy BMI range?
There's no "better" end — both 18.5–24.9 are healthy. Choose a weight where you feel strong, energised, and can maintain it long-term through balanced diet and activity. Extreme targets often lead to unsustainable patterns.
What if my ideal weight doesn't match my BMI calculation?
This can happen if you have high muscle mass (muscle weighs more than fat). Discuss your personal target with your GP, who can assess your overall health rather than relying on numbers alone.
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.