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
Working Out The Square Metre — A UK Health Guide
Working out the square metre is an important calculation in clinical health assessments, particularly when determining medication doses and monitoring body surface area. This UK health guide explains what square metres mean in a health context, why they matter, and how to calculate them accurately. Understanding this measurement helps you have more informed conversations with your GP or healthcare professional about personalised dosing and health assessments.
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.
Why Square Metres Matter in UK Health Assessments
Body surface area (BSA) is measured in square metres and is used by healthcare professionals for several important reasons. Unlike simple weight measurements, BSA accounts for both your height and weight together, making it more accurate for calculating safe medication doses, particularly for certain injectable treatments and chemotherapy. The NHS and clinical guidelines use BSA to personalise treatment plans.
Square metres are also relevant if you're discussing body composition or monitoring health changes over time. Healthcare professionals may reference your BSA when:
- Calculating appropriate medication dosing
- Assessing cardiovascular risk factors
- Monitoring treatment effectiveness
- Determining nutritional requirements
Your GP can calculate your BSA using your height and weight, or you can work it out yourself using a simple formula. Knowing your square metre measurement gives you better context for understanding your health assessments and personalised health guidance.
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.
How to Calculate Your Body Surface Area
The most common formula used in UK healthcare is the Mosteller formula, which is straightforward and widely accepted: BSA (m²) = √[(height in cm × weight in kg) ÷ 3,600].
For example, if you weigh 75 kg and are 170 cm tall: √[(170 × 75) ÷ 3,600] = √3.54 = 1.88 m². Most adults fall between 1.5 and 2.5 square metres. Your weight converter and BMI calculator on this page can help you confirm your measurements in the right units. If you're unsure about your calculations, your GP can confirm your BSA instantly using their clinical systems. This measurement becomes especially important if you're considering or using injectable health treatments where dosing is BSA-adjusted.
- 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 a square metre in health terms?
A square metre (m²) is a measurement of body surface area (BSA) used in healthcare. It combines your height and weight to give a more precise assessment than weight alone. BSA is used to calculate safe medication doses and monitor health changes. Most UK adults have a BSA between 1.5 and 2.5 square metres.
Why do healthcare professionals use square metres?
Square metres account for both height and weight, making them more accurate than weight alone for determining safe medication doses. The NHS uses BSA particularly for injectable treatments, personalised dosing, and assessing cardiovascular risk. It's a more precise clinical measurement for tailoring healthcare to your individual body size.
How do I calculate my body surface area?
Use the Mosteller formula: BSA (m²) = √[(height in cm × weight in kg) ÷ 3,600]. For example, at 75 kg and 170 cm tall, your BSA would be approximately 1.88 m². Your GP can also calculate this instantly using their clinical systems if you'd prefer professional confirmation.
Is body surface area the same as BMI?
No — they're different measurements. BMI only uses weight and height to calculate a general health category. BSA (body surface area) calculates your actual surface area in square metres, which is more precise for medication dosing and clinical assessment. Use our free BMI calculator to check your BMI alongside discussing BSA with your GP.
Do I need to know my square metres for weight management?
For general weight management, your weight and BMI are usually sufficient. However, if you're being assessed for prescription weight loss treatment or injectable medications, your healthcare professional may reference BSA for personalised dosing. Your GP will guide you on whether BSA is relevant to your individual health plan.
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.