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
How To Find Out Your BMR
Your BMR (basal metabolic rate) 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 useful for weight management planning, as it shows you how many calories you need daily before any physical activity. Several straightforward formulas can help you calculate it, and knowing your BMR can guide you towards sustainable healthy weight decisions aligned with NHS health guidance.
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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 BMR
The most widely used BMR formula is the Mifflin-St Jeor equation, which is more accurate than older formulas like Harris-Benedict:
- Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
For example, a 35-year-old woman weighing 70kg and 165cm tall would calculate: (10 × 70) + (6.25 × 165) − (5 × 35) − 161 = 700 + 1031.25 − 175 − 161 = 1,395 calories per day. You can use our free BMI calculator above to check your weight context, and then apply this formula to find your personalised BMR.
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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 tells you your basal calorie requirement — the minimum you need to eat to maintain basic body functions. To lose weight sustainably, NHS guidance suggests creating a deficit of approximately 500 calories per day below your total daily energy expenditure (which includes activity on top of BMR), resulting in roughly 0.5–1kg loss per week. Understanding your BMR helps you set realistic calorie targets and avoid eating too little, which can slow metabolism and cause muscle loss. This is especially important if you're considering any weight management approach, including lifestyle changes or discussing options with your GP.
- 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.
Is BMR the same as metabolism?
No. Your BMR is the calories burned at complete rest. Your total daily energy expenditure (TDEE) is BMR plus calories burned through activity. TDEE is what matters for weight loss planning.
Can I check my BMR without doing the maths?
Yes — some fitness trackers and smartwatches estimate BMR. However, the Mifflin-St Jeor formula is the most reliable. Our weight converter and BMI calculator can help you verify your measurements are accurate before calculating.
Does BMR change with age?
Yes. BMR decreases by approximately 2–8% per decade after age 30, partly due to muscle loss. This is why older adults often need fewer calories than younger people of the same weight.
How does BMR relate to healthy weight?
BMR doesn't determine healthy weight — that's based on BMI and health. But knowing your BMR helps you eat appropriately for your healthy weight target. Use our BMI calculator to find your healthy weight range first.
Should I eat below my BMR to lose weight faster?
No. Eating consistently below your BMR can slow metabolism, cause muscle loss, and lead to nutritional deficiency. NHS guidance recommends a modest deficit of 500 calories below your total daily expenditure, not below BMR itself. Speak to your GP if you're unsure about safe calorie targets.
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.