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 Calories For Weight Loss
Calculating calories for weight loss is one of the most practical ways to manage your weight in the UK. The basic principle is simple: to lose weight, you need to consume fewer calories than your body burns. The NHS recommends aiming for a calorie deficit of approximately 500 calories per day, which typically results in losing around 0.5 to 1 kg per week — a safe and sustainable rate. However, individual needs vary based on age, activity level, metabolism, and current weight. Our free BMI calculator and weight loss tools can help you understand your personal starting point and set realistic goals.
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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 Calorie Deficits and Weight Loss
A calorie deficit is the difference between the calories you consume and the calories your body burns each day. To lose weight, you need to create this deficit consistently over time.
- 500 kcal/day deficit = approximately 0.5 kg weight loss per week
- 750 kcal/day deficit = approximately 0.75 kg weight loss per week
- 1000 kcal/day deficit = approximately 1 kg weight loss per week (maximum safe rate recommended by NHS)
Your daily calorie needs depend on your basal metabolic rate (BMR) — the calories your body burns at rest — plus activity level. A typical UK adult woman burns 1400–1800 kcal daily; a typical man burns 1700–2200 kcal daily. To find your specific needs, use your current weight, height, age, and activity level. Many people underestimate calorie intake, so tracking food for at least a few weeks can reveal where you actually stand. Weight loss medication such as GLP-1 injections may support this process by reducing appetite, but they work best alongside reduced-calorie intake and increased physical activity.
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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.
Practical Steps to Calculate and Track Your Calories
Start by calculating your estimated daily calorie needs using an online calculator (many are available free) or asking your GP for guidance. Once you know this, decide on your target deficit — the NHS suggests 500 kcal/day for most adults. Use a food tracking app or food diary to log what you eat for one week to establish your baseline. Many people find this surprisingly eye-opening. Then, gradually reduce intake by swapping high-calorie foods for lower-calorie alternatives: choose whole grains over refined carbs, lean proteins over fatty cuts, and add more vegetables. Track your weight weekly using our free progress tracker — remember that weight naturally fluctuates, so look at the trend over 2–3 weeks rather than daily changes. If you have a BMI in the overweight or obese range for UK weight management, discuss prescription weight loss options with your GP as part of a comprehensive approach to achieving your goal.
- 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.
How many calories should I eat per day to lose weight?
This depends on your individual basal metabolic rate (BMR) and activity level. A typical approach is to eat 500 kcal less than your body burns daily, resulting in approximately 0.5 kg weight loss per week. Use your current weight, height, age, and activity level to estimate your daily needs — your GP can also help calculate this. The NHS recommends not dropping below 1200 kcal/day without medical supervision.
Is a 1000 calorie daily deficit safe?
The NHS recommends a maximum safe weight loss rate of 1 kg per week, which requires approximately a 1000 kcal/day deficit. This is safe for most adults in the short term, but very low calorie diets (under 800 kcal/day) should only be followed under medical supervision. gradual weight management increases the risk of muscle loss, nutritional deficiencies, and gallstones. Slower, gradual loss (0.5–1 kg/week) is more sustainable long-term.
How do I know my daily calorie burn?
Your daily calorie burn (TDEE — total daily energy expenditure) depends on your basal metabolic rate plus activity level. Online TDEE calculators use your weight, height, age, sex, and activity level to estimate this. For a quick reference: a typical UK adult woman burns 1400–1800 kcal daily; a typical man burns 1700–2200 kcal daily. Your GP or a registered dietitian can provide a personalised estimate.
Does weight loss medication reduce the need to count calories?
Prescription weight loss medications like GLP-1 injections (such as Wegovy) may help reduce appetite and food cravings, making it easier to eat fewer calories. However, they work most effectively alongside a reduced-calorie diet and increased physical activity — not as a replacement. Clinical trials show that people taking weight loss medication alongside lifestyle changes achieve better results than either approach alone. Medication requires a prescription and clinical assessment.
How can I track my weight loss progress?
Track your weight weekly at the same time of day on the same scales — morning, after the toilet, before eating is typical. Record the figure in a food diary or use our free progress tracker on this site. Weight naturally fluctuates daily due to water, food, and hormones, so look at the average trend over 2–3 weeks rather than individual daily readings. Aim for 0.5–1 kg loss per week as a realistic, healthy target.
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.