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 Basal Metabolic Rate
Your basal metabolic rate (BMR) is the number of calories your body burns at rest just to maintain basic functions like breathing, circulation, and cell production. Understanding your BMR is essential for effective weight management and creating a sustainable calorie deficit. This UK health guide explains what BMR is, how to calculate it, and why it matters for your overall health and nutrition planning.
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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 to Calculate Your Basal Metabolic Rate
There are several established formulas for calculating BMR, with the Mifflin-St Jeor equation being the most accurate for modern populations. This formula accounts for your weight (in kg), height (in cm), age (in years), and sex.
- For men: BMR = (10 × weight) + (6.25 × height) − (5 × age) + 5
- For women: BMR = (10 × weight) + (6.25 × height) − (5 × age) − 161
For example, a 35-year-old man weighing 80kg and standing 175cm tall would have a BMR of approximately 1,760 calories per day. The older Harris-Benedict equation is slightly less accurate but still widely used. Once you know your BMR, multiply it by your activity factor (typically 1.2–1.9) to calculate your total daily energy expenditure (TDEE) — the total calories you burn including exercise.
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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.
Why BMR Matters for Weight Management
Your BMR represents the metabolic foundation of your weight management strategy. A higher BMR means you naturally burn more calories at rest, making weight loss easier to achieve. Factors like age, muscle mass, genetics, and hormones all influence BMR — which is why two people of the same weight and height may have different calorie needs.
Understanding your BMR helps you set realistic calorie targets. The NHS recommends a moderate calorie deficit of around 500 kcal per day for sustainable weight loss of approximately 0.5kg per week. Use our free BMI calculator alongside BMR calculations to gain a complete picture of your health metrics and weight management baseline.
- 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 BMR and TDEE?
BMR is calories burned at rest; TDEE (total daily energy expenditure) includes activity on top of BMR. To find TDEE, multiply your BMR by your activity factor: sedentary (1.2), lightly active (1.375), moderately active (1.55), very active (1.725), or extremely active (1.9). TDEE tells you total daily calorie burn.
How accurate are BMR calculators?
The Mifflin-St Jeor equation is accurate within approximately ±10–20% for most people. Online BMR calculators using this formula are generally reliable, though individual variation exists. Indirect calorimetry (measured in labs) is more precise but impractical for general use. Use calculated BMR as a starting point and adjust based on real-world results.
Does BMR change with age?
Yes. BMR naturally decreases by approximately 2% per decade after age 30, partly due to age-related muscle loss. This is why weight management can become harder as you age. Maintaining muscle through strength training and adequate protein intake can help preserve BMR and support healthier weight management throughout life.
Can I increase my BMR?
You can moderately increase BMR by building muscle mass through resistance training and ensuring adequate protein intake. BMR is largely determined by genetics, body composition, and hormones — it cannot be dramatically increased. Focus on sustainable lifestyle changes: balanced nutrition, regular physical activity, quality sleep, and stress management for best long-term results.
How does BMR relate to weight loss injections like Mounjaro or Wegovy?
Weight loss injections work alongside your BMR and calorie deficit — they don't replace it. These prescription-only medications may help reduce appetite and food cravings, making it easier to maintain a calorie deficit. Clinical trials showed Wegovy helped participants lose approximately 15% body weight, but results were achieved with reduced-calorie diet and increased physical activity combined with medication.
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.