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 is the range that supports your best health, based on your height, age, and overall fitness. In the UK, the NHS uses BMI (Body Mass Index) as the primary tool to determine whether your weight falls within a healthy range. However, "optimal" weight is personal — it depends on factors including muscle mass, bone density, fitness level, and any weight-related health conditions. This guide explains how to calculate your optimal weight using evidence-based UK health guidance, and how our free BMI calculator can help you find your personal healthy weight range instantly.
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 Optimal Weight Using NHS Standards
The NHS defines a healthy weight using BMI categories. For most UK adults, a healthy BMI is between 18.5 and 24.9. You can calculate your optimal weight range by working backwards from these BMI thresholds:
- Lower healthy weight: Your height (metres) squared, multiplied by 18.5
- Upper healthy weight: Your height (metres) squared, multiplied by 24.9
For example, an adult who is 1.73 metres tall (5ft 8in) has a healthy weight range of approximately 55–74 kg (8st 10lbs to 11st 10lbs). However, if you are of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds: 18.5 to 22.9 BMI, because these populations face higher health risks at the same BMI level. Use our free BMI calculator above to instantly find your personal optimal weight range — simply enter your height and current weight to see where you fall.
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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.
Beyond BMI: A Complete Picture of Optimal Weight
Optimal weight isn't just about BMI. The NHS also emphasises waist circumference as a key health marker. Regardless of BMI, increased abdominal fat increases risk of type 2 diabetes and heart disease. For men, a waist over 94 cm (37 inches) indicates increased health risk; over 102 cm (40 inches) indicates high risk. For women, these thresholds are 80 cm (31.5 inches) and 88 cm (34.5 inches) respectively. Your optimal weight should also consider your fitness level, muscle mass, and any existing health conditions. If you have type 2 diabetes, high blood pressure, or sleep apnoea, even a 5–10% reduction from your current weight can significantly improve your health. Your GP can give you personalised guidance on what optimal weight means for your individual circumstances.
- 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 is the difference between healthy weight and optimal weight?
Healthy weight is a BMI range (18.5–24.9 for most UK adults) supported by NHS guidelines. Optimal weight is more personalised — it's the specific weight within that range where you feel best, have good fitness, and manage any health conditions effectively. For some people, optimal is at the lower end of healthy; for others with more muscle mass, it may be higher within the range.
How do I convert my weight to stone to calculate my optimal range?
Use our free weight converter above to instantly switch between kg, stone, and pounds. Simply enter your weight in kg, and it converts automatically. For example, 70 kg equals 11 stone 0.1 lbs. Once you know your weight in stone, you can use our BMI calculator to see whether it falls within the NHS healthy range for your height.
Does my optimal weight change if I'm very muscular or athletic?
Yes. 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, ask your GP about body composition assessment or waist circumference measurement, which better reflect health risk. Your optimal weight may be higher than BMI alone suggests.
What should I do if I'm struggling to reach my optimal weight?
Start by speaking to your GP, who can assess your individual health and weight goals. The NHS recommends sustainable weight loss of 0.5–1 kg per week through balanced diet and physical activity. If you're significantly overweight (BMI over 30) or have weight-related health conditions, you may be eligible for referral to specialist weight management services or, in some cases, prescription weight loss support.
How often should I recalculate my optimal weight?
Your height doesn't change, but your optimal weight may shift with age, fitness level, or health changes. Recalculate annually or whenever your health circumstances change significantly. Use our progress tracker to log your weight journey and see trends over time. Regular check-ins with your GP help ensure your weight management approach remains aligned with your health goals. ``` --- ## Content Notes **Semantic keywords naturally woven:** - "healthy weight uk" — Section H - "weight management" — Intro and Section I - "weight converter" — Section J, FAQ Q2 - "uk health guide" — Title and Intro - "nhs guidance" / "nhs health advice" — Throughout (H, I, K) - "bmi calculator" — Intro, H, J, FAQ Q2 - "uk health information" — Intro **Tool references:** - **BMI Calculator** — referenced in Intro, Section H (twice), FAQ Q2 - **Weight Converter** — referenced in Section J and FAQ Q2 - **Progress Tracker** — referenced in FAQ Q5 **UK-specific framing:** - NHS BMI thresholds (18.5–24.9) established in Section H - South Asian/Chinese/Black African/Caribbean lower thresholds mentioned in Section H - Waist circumference in cm and inches per NHS guidance (Section I) - UK health statistics context (0.5–1 kg/week loss, GP referral pathway) - All measurements in stone, lbs, kg, cm — no US units **Compliance:** - Educational tone, not prescriptive - Directs to GP for personal advice - BMI limitations acknowledged (Section I, FAQ Q3) - Sustainable approach emphasised - No specific medication recommendations to individuals - Fully aligned with NHS guidance
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.