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
BMR Calculator UK — What Is Your Basal Metabolic Rate?
Your basal metabolic rate (BMR) is the number of calories your body burns at rest just to maintain essential functions like breathing, circulation, and cell production. Understanding your BMR is a key part of UK health information and weight management planning. It forms the foundation for calculating your total daily energy expenditure and helps you determine the right calorie intake for sustainable weight loss or maintenance. This UK health guide explains how BMR works and how to calculate yours.
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 BMR — The Mifflin-St Jeor Formula
The most accurate BMR formula used in the UK is the Mifflin-St Jeor equation, which is preferred over older formulas like Harris-Benedict because it accounts for modern lifestyles and body composition more accurately.
For men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
For women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
Once you have your BMR, multiply it by your activity factor to find your total daily energy expenditure (TDEE). For weight management planning, subtract 500 kcal per day from your TDEE for sustainable weight loss of approximately 0.5 kg per week — aligned with NHS guidance. Use our free BMI calculator alongside BMR calculations to get a complete picture of your current health status and weight management goals.
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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.
BMR vs TDEE — Understanding Your Daily Calorie Needs
BMR is what you burn at complete rest — it does not include everyday activities. TDEE (Total Daily Energy Expenditure) includes BMR plus all movement throughout the day, from walking to exercise.
Your activity factor multiplies your BMR:
- Sedentary (little exercise): BMR × 1.2
- Lightly active (1–3 days/week): BMR × 1.375
- Moderately active (3–5 days/week): BMR × 1.55
- Very active (6–7 days/week): BMR × 1.725
- Extremely active (twice daily training): BMR × 1.9
For accurate weight management, calculate both figures and use them to set realistic calorie targets. Our weight converter tool helps you track progress in your preferred units — stone, lbs, or kg.
- 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 BMR and why does it matter for weight loss?
BMR (basal metabolic rate) is the calories your body burns at rest maintaining vital functions. It matters for weight loss because it's the baseline for calculating your total daily calorie needs. Knowing your BMR helps you create an appropriate calorie deficit (typically 500 kcal/day for sustainable 0.5 kg weekly loss) as recommended by NHS guidance.
Does age affect BMR?
Yes. BMR typically decreases with age — approximately 2% per decade after age 20. This is because muscle mass naturally declines over time. Maintaining muscle through strength training can help slow this decline and preserve metabolism.
Is BMR the same as metabolism?
No. BMR is a specific measurement of calories burned at rest. Metabolism is broader — it includes BMR plus energy used for digestion (thermic effect of food) and all daily activities. Your total daily energy expenditure (TDEE) is a more complete picture of your metabolism.
Can BMR change?
Yes. BMR changes with age, weight, muscle mass, and hormonal factors. Building muscle increases BMR because muscle tissue is more metabolically active than fat. Weight loss can temporarily lower BMR, but this effect normalises over time.
How accurate are BMR calculators?
The Mifflin-St Jeor formula is approximately 90% accurate for most people. Individual variation exists due to genetics, body composition, and metabolic differences. BMR calculations are useful estimates — pair them with practical tracking using our free progress tracker to monitor real-world results.
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.