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 Calculate Macros For Weight Loss
Calculating your macronutrient breakdown is a practical way to support weight loss whilst maintaining muscle and energy levels. Macros — short for macronutrients (protein, carbohydrates, and fats) — work alongside a calorie deficit to help you lose weight in a sustainable way. This guide walks you through calculating your ideal macro ratios based on your goals, activity level, and current weight. When combined with consistent tracking and lifestyle changes, a macro-balanced approach can be more effective than calorie counting alone.
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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.
Understanding Your Three Macronutrients
Protein is essential for preserving muscle mass during weight loss. Aim for 1.6–2.2g of protein per kilogram of body weight daily — higher intakes support muscle retention when eating in a calorie deficit. Carbohydrates fuel your workouts and brain function; most people do well with 2–4g per kg of body weight depending on activity level. Fats support hormone production and nutrient absorption — aim for at least 0.8g per kg of body weight. The NHS recommends a balanced approach rather than extreme restriction of any macronutrient.
- Protein: preserves muscle, increases satiety, has a higher thermic effect (burns more calories during digestion)
- Carbs: provide energy for exercise and daily activity
- Fats: essential for hormone balance and brain health
Your exact macro ratio depends on your fitness goals, activity level, and personal preference. There is no single "perfect" ratio — flexibility and consistency matter more than precision.
Clinically BackedWeight 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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Step-by-Step Macro Calculation
Step 1: Calculate your daily calorie needs. Use your basal metabolic rate (BMR) or total daily energy expenditure (TDEE) as your starting point. Most weight loss involves a deficit of 300–500 kcal per day. Calculate your personal healthy weight range and BMI using our free BMI calculator above to understand where you are now.
Step 2: Assign your macro percentages. A common balanced split for weight loss is 40% protein, 35% carbs, 25% fats. Convert these percentages to grams: multiply your calorie target by the percentage, then divide by the calories per gram (protein and carbs = 4 kcal/g; fat = 9 kcal/g).
Step 3: Track and adjust. Use a tracking app like MyFitnessPal or Cronometer for 2–3 weeks, then assess your progress. If weight loss stalls, reduce calories by 100–150 kcal and re-evaluate after another 2 weeks. Use our free progress tracker to monitor trends over time.
- 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 best macro ratio for weight loss?
There is no single "best" ratio — it depends on your activity level, preferences, and lifestyle. A common starting point is 40% protein, 35% carbs, 25% fats. The most important factor is maintaining a calorie deficit whilst hitting adequate protein intake to preserve muscle. Experiment for 3–4 weeks and adjust based on your energy levels, hunger, and progress.
How does protein help with weight loss?
Protein helps preserve muscle mass during a calorie deficit, keeps you feeling fuller for longer, and has a higher thermic effect — meaning your body burns more calories digesting protein compared to carbs or fats. The NHS recommends higher protein intake during weight loss. Aim for 1.6–2.2g per kg of your current body weight daily.
Should I use a macro calculator or calculate manually?
Both work. Online macro calculators are quick and convenient — you input your weight, height, activity level, and goal, and they calculate your targets. a UK pharmacy calculation gives you more control and understanding of the process. For most people, a calculator combined with tracking apps like MyFitnessPal is the easiest approach.
Can I lose weight without counting macros?
Yes. Weight loss fundamentally requires a calorie deficit — macros are secondary. Many people lose weight by simply eating whole foods, controlling portion sizes, and being active. Macro counting is useful if you want to preserve muscle, optimise energy for exercise, or have specific fitness goals, but it's not essential for basic weight loss.
How does prescription weight loss medication fit with macro tracking?
Prescription weight loss medications like those used in NHS weight management programmes or GLP-1 weight loss medication work alongside dietary changes, not instead of them. Macro tracking can still be helpful to ensure you're meeting your nutritional needs whilst on medication. If taking prescription weight loss treatment, your prescriber will advise on dietary support. Ask your GP or a registered dietitian for personalised guidance.
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.