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
Calories Weight Loss Calculator: How Many Calories to Lose Weight?
Understanding how calories affect weight loss is the foundation of sustainable weight management in the UK. A calorie deficit—eating fewer calories than your body burns—is essential for losing weight. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week, which typically requires a deficit of around 500 calories per day. This guide explains how to calculate your calorie needs, how weight loss medication like GLP-1 injections can support your goals, and how to use our free tools to track your progress.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Many Calories Do You Need to Lose Weight?
Your daily calorie needs depend on your age, sex, height, current weight, and activity level. The NHS recommends a calorie deficit of approximately 500 kcal per day to lose around 0.5 kg (1 lb) per week—a safe and sustainable rate. To calculate your personal calorie needs, multiply your weight in kg by 24 for a rough baseline, then adjust for activity level. A sedentary person might multiply by 1.3–1.5, while someone moderately active multiplies by 1.5–1.75.
- Basal metabolic rate (BMR): The calories your body burns at rest, typically 1,200–1,800 kcal/day for women and 1,500–2,200 kcal/day for men
- Total daily energy expenditure (TDEE): BMR multiplied by your activity factor; this is what you'd consume to maintain current weight
- Weight loss target: Subtract 500 kcal from TDEE to lose approximately 0.5 kg per week
The key is consistency over perfection. Even a 300–400 kcal daily deficit, combined with increased physical activity and support from weight management UK services, can produce meaningful results over time. Use our free BMI calculator to establish your current health status and target weight range.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Weight Loss Medication and Calorie Reduction
Prescription weight loss medication can support calorie reduction by helping you feel fuller longer and reducing food cravings. GLP-1 medications like Wegovy (semaglutide) and Mounjaro (tirzepatide) are licensed for weight management in the UK and work alongside dietary changes—not instead of them. Clinical trials showed that adults using GLP-1 weight loss medication lost an average of 15–20% of their body weight over 68 weeks when combined with a reduced-calorie diet and increased physical activity. Access to prescription weight loss UK is available through NHS specialist services or private assessment. Our GLP-1 weight loss calculator can help you estimate potential results at different doses. Always consult your GP before starting any medication.
- 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 per day should I eat to lose weight safely?
The NHS recommends a deficit of around 500 calories per day for safe, sustainable loss of 0.5–1 kg per week. Calculate your total daily energy expenditure first (using your BMR and activity level), then subtract 500 kcal. Avoid dropping below 1,200 kcal/day without medical supervision, as this risks nutrient deficiencies and muscle loss.
Can I lose weight without counting calories?
Yes. Focusing on whole foods, portion control, regular physical activity, and eating slowly can support weight loss without precise calorie counting. However, awareness of calorie content helps most people. Our BMI calculator and progress tracker help you monitor health markers beyond just calories.
How do GLP-1 medications like Wegovy fit into calorie reduction?
GLP-1 medications are prescription-only treatments that help reduce appetite and food cravings, making it easier to maintain a calorie deficit. They are not a replacement for dietary changes. Clinical trials showed they work best alongside a reduced-calorie diet and exercise. Your prescriber will assess whether you're eligible.
What's the difference between a calorie deficit and a very low-calorie diet?
A moderate calorie deficit (500 kcal/day) is sustainable long-term and supports healthy weight loss of 0.5–1 kg/week. A very low-calorie diet (under 800 kcal/day) is used only under medical supervision for gradual weight management, typically in specialist NHS weight loss services, and carries higher risks of muscle loss and nutrient deficiency.
How can I track my calorie intake and weight loss progress?
Use a food diary app (MyFitnessPal, Cronometer) to log meals, or keep a simple written record. Track your weight weekly using our free progress tracker to monitor trends over time. Take measurements and photos as well—weight alone doesn't show muscle gain or body composition changes. Share regular updates with your GP 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.