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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RMR Calculator — Understanding Your Resting Metabolic Rate
Your resting metabolic rate (RMR) is the number of calories your body burns at rest just to maintain basic functions like breathing, circulation, and cell production. Knowing your RMR is valuable for understanding your daily energy needs and supporting weight management decisions. This UK health guide explains what RMR means, how it's calculated, and how it fits into the NHS guidance for healthy weight management. Whether you're managing your weight independently or considering prescription weight loss options, understanding your metabolic baseline helps you make informed choices about diet and activity levels.
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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.
What Is RMR and Why Does It Matter?
Resting metabolic rate (RMR) is the number of calories your body uses while at complete rest to maintain essential functions like heartbeat, breathing, digestion, and cell repair. It accounts for approximately 60–75% of your total daily energy expenditure for most people, making it the largest component of your overall calorie burn.
RMR differs from basal metabolic rate (BMR) — BMR is measured under very strict laboratory conditions, whilst RMR is measured under more relaxed conditions and is slightly higher. For practical weight management purposes, the terms are often used interchangeably.
Understanding your RMR helps you:
- Calculate how many calories you need daily to maintain your current weight
- Determine the calorie deficit needed for sustainable weight loss (typically 500 kcal/day for ~0.5 kg weekly loss)
- Identify whether your weight management approach aligns with NHS guidance
- Make informed decisions about diet and exercise planning
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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.
How to Calculate Your RMR — UK Methods
The most commonly used formula for estimating RMR is the Mifflin-St Jeor equation, which accounts for age, sex, height, and weight. This is the gold standard for UK and international health guidance.
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 RMR, multiply it by your activity level factor (1.2–1.9) to estimate your total daily energy expenditure. Use our free BMI calculator alongside this calculation to understand your healthy weight range, and consider our weight converter to cross-reference your measurements in stone, pounds, and kilograms for easy tracking with UK health resources.
- 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 RMR and BMI?
RMR (resting metabolic rate) measures daily calories burned at rest — it's about energy expenditure. BMI (body mass index) is a screening tool that compares height to weight to assess whether your weight falls in a healthy range. Both are useful: BMI shows if weight loss might benefit your health, while RMR helps you understand how to achieve it through calorie balance. Calculate your BMI with our free BMI calculator on this page.
Does RMR change with age?
Yes. RMR decreases with age — typically by 2–8% per decade after age 30, primarily because muscle mass naturally declines with age. This is why older adults often need fewer calories to maintain weight. Regular physical activity, including strength training, helps preserve muscle mass and support RMR as you age.
How does RMR relate to weight loss on NHS guidance?
The NHS recommends a calorie deficit of approximately 500 kcal per day for sustainable weight loss of 0.5–1 kg weekly. Knowing your RMR helps you calculate this deficit accurately. If your RMR is 1,500 kcal, a 2,000 kcal daily intake creates the recommended deficit. NHS guidance emphasises sustainable approaches alongside lifestyle changes, not rapid restriction.
Can RMR help if I'm considering weight loss medication?
Yes. Understanding your RMR provides baseline context for your metabolic health. If you're eligible for prescription weight loss treatment like GLP-1 medications (Mounjaro or Wegovy), knowing your RMR helps you and your prescriber understand your starting point. These medications work alongside calorie reduction and increased activity — your RMR helps guide realistic calorie targets.
Should I consult my GP about my RMR?
If you're making significant diet or activity changes, or if you're considering weight loss support, discussing your RMR and overall metabolic health with your GP is valuable. Your GP can assess whether your weight management approach aligns with NHS guidance and whether you might benefit from tier 3 specialist services or prescription support options available in your area.
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.