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
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How to Work Out Your BMR
Your basal metabolic rate (BMR) is the number of calories your body burns at rest just to keep you alive. Understanding your BMR is a useful starting point for weight management and healthy weight UK planning, as it shows how many calories you need daily before any physical activity. This nhs health advice guide explains the simple formulas you can use to calculate your BMR in minutes, plus how to use that number for practical weight management decisions.
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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.
BMR Calculation Formulas
Two widely used formulas can estimate your BMR. The Mifflin-St Jeor equation (considered most accurate for average adults) and the Harris-Benedict formula (older but still useful) both require your age, sex, height, and weight in kilograms.
Mifflin-St Jeor for men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
Mifflin-St Jeor for women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
For example, a 30-year-old woman who is 165cm tall and weighs 70kg would calculate: (10 × 70) + (6.25 × 165) − (5 × 30) − 161 = approximately 1,490 kcal per day. This means her body burns around 1,490 calories daily at complete rest, before any movement or exercise.
The result gives you your daily baseline calorie burn — essential information for understanding weight management and creating a sustainable calorie deficit if you're planning weight loss.
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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.
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Using Your BMR for Weight Management
Your BMR is only part of the picture. To estimate total daily calorie burn, multiply your BMR by an activity factor: sedentary (BMR × 1.2), lightly active (BMR × 1.375), moderately active (BMR × 1.55), or very active (BMR × 1.9).
For sustainable weight loss, the NHS recommends a calorie deficit of around 500 kcal daily, which typically results in approximately 0.5kg lost per week. Our free BMI calculator can show you whether you're in a healthy weight UK range, and our weight converter helps you track progress across kg, stone, and lbs. Combined with nhs guidance on nutrition and physical activity, understanding your BMR creates a solid foundation for evidence-based weight management decisions.
- 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 complete rest. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by your activity level. TDEE is what you actually burn daily with normal activity and exercise. Both are useful for weight management planning.
Is BMR calculation accurate for everyone?
Formulas like Mifflin-St Jeor are estimates based on average populations. Individual BMR varies due to muscle mass, metabolism, and genetics. A formula gives you a reasonable starting point, but adjusting based on real weight change over 2–4 weeks is more accurate.
Does BMR change with age?
Yes. BMR decreases approximately 2–8% per decade after age 30 due to muscle loss. This is why weight management often requires adjustments as you get older. Maintaining muscle through strength training can help preserve BMR.
How does weight loss medication fit with BMR calculations?
Weight loss medications like those used in nhs health advice and weight management programmes work alongside calorie deficit. They may help reduce appetite, making it easier to maintain the calorie deficit your BMR calculation suggests you need for sustainable weight loss.
Should I use my current weight or goal weight in the BMR formula?
Always use your current weight for an accurate BMR reading. Your BMR will change as you lose or gain weight, so recalculate every 5–10kg of weight change to keep your calorie targets accurate and relevant.
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.