How do I calculate my calorie deficit?

To calculate your calorie deficit: 1) First, determine your TDEE (Total Daily Energy Expenditure) using factors like age, weight, height, and activity level. 2) Subtract your desired daily deficit from your TDEE. A 500 calorie daily deficit typically results in about 0.5kg of weight loss per week. Our calculator uses the Mifflin-St Jeor equation, which is considered one of the most accurate methods.

What is a healthy calorie deficit?

A healthy calorie deficit is typically 300-500 calories below your TDEE, resulting in 0.25-0.5kg of weight loss per week. The NHS recommends losing no more than 0.5-1kg per week for sustainable weight loss. Very large deficits (over 1,000 calories) can lead to muscle loss, nutritional deficiencies, and metabolic slowdown. Always ensure you're eating at least 1,500 calories (men) or 1,200 calories (women) daily.

How many calories do I need to cut to lose 1kg?

To lose 1kg of body fat, you need to create a total deficit of approximately 7,700 calories. This is because 1kg of fat contains about 7,700 calories of stored energy. To lose 1kg per week, you would need a daily deficit of about 1,100 calories (7,700 ÷ 7 days). However, the NHS recommends a more gradual approach of 0.5kg per week for sustainable results.

Does a calorie deficit actually work for weight loss?

Yes, a calorie deficit is the fundamental principle of weight loss, supported by extensive scientific research. When you consistently consume fewer calories than you burn, your body must use stored energy (fat) to make up the difference. While factors like hormones and metabolism can affect the rate, creating a calorie deficit is the only proven way to lose weight. Combining a moderate deficit with adequate protein intake and exercise helps preserve muscle mass.

What is BMR and why does it matter?

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest just to maintain vital functions like breathing, circulation, and cell production. It typically accounts for 60-75% of your total daily calorie burn. Understanding your BMR helps set realistic calorie targets - you should never eat below your BMR as this can slow your metabolism and cause health issues.

What is TDEE and how is it different from BMR?

TDEE (Total Daily Energy Expenditure) is the total number of calories you burn in a day, including all activities. It's calculated by multiplying your BMR by an activity factor. For example, if your BMR is 1,500 and you're moderately active (factor of 1.55), your TDEE would be about 2,325 calories. Your TDEE is what you should base your calorie deficit on, not your BMR.

How fast can I safely lose weight?

According to NHS guidelines, a safe rate of weight loss is 0.5 to 1kg per week. Losing weight faster than this can result in muscle loss, nutritional deficiencies, gallstones, and a slower metabolism. Rapid weight loss is also harder to maintain long-term. Our calculator limits recommendations to a maximum of 1kg per week to ensure your plan is both effective and safe.

Why is protein important when in a calorie deficit?

When you're in a calorie deficit, your body may break down muscle for energy alongside fat. Eating adequate protein (1.6-2.2g per kg of body weight) helps preserve muscle mass during weight loss. This is important because muscle is metabolically active - the more muscle you have, the more calories you burn at rest. High protein intake also helps you feel fuller for longer, making it easier to stick to your calorie target.

Why has my weight loss stalled (plateau)?

Weight loss plateaus are common and can happen for several reasons: 1) As you lose weight, your TDEE decreases, so your previous deficit becomes smaller. 2) Your body adapts to sustained calorie restriction by reducing non-exercise activity. 3) Water retention can mask fat loss temporarily. Solutions include recalculating your TDEE at your new weight, slightly increasing activity, or taking a brief "diet break" at maintenance calories before resuming your deficit.

Should I exercise while in a calorie deficit?

Yes, exercise is highly beneficial during a calorie deficit. Resistance training helps preserve muscle mass, while cardio increases your calorie burn. However, don't overdo it - excessive exercise combined with severe calorie restriction can lead to burnout and muscle loss. Aim for 2-3 strength training sessions and 150 minutes of moderate cardio per week. Remember, you cannot out-exercise a bad diet - nutrition is the primary driver of weight loss.

Do I need to track every calorie?

While tracking calories can be helpful, especially when starting out, it's not required for everyone. Some people find it creates an unhealthy relationship with food. Alternative approaches include portion control, using your hand as a measuring guide, or following structured meal plans. The key is finding a sustainable approach that creates a consistent calorie deficit without causing excessive stress or obsession.

What is the minimum number of calories I should eat?

The NHS recommends never going below 1,500 calories per day for men or 1,200 calories per day for women without medical supervision. Eating too few calories can cause nutrient deficiencies, muscle loss, hormonal disruptions, and metabolic adaptation. Very low calorie diets (VLCDs) of 800 calories or less should only be followed under medical supervision for specific health conditions.

What are the NHS guidelines for calorie deficit and weight loss?

The NHS guidelines recommend: 1) Aiming for a weight loss of 0.5-1kg per week. 2) Creating a daily deficit of 500-600 calories. 3) Not going below 1,500 calories (men) or 1,200 calories (women) without medical advice. 4) Combining dietary changes with regular physical activity. 5) Making sustainable lifestyle changes rather than following fad diets. 6) Consulting a GP before starting a weight loss programme if you have underlying health conditions.

How long until I see results from a calorie deficit?

You may notice initial changes within 1-2 weeks, though this is often water weight. Noticeable fat loss typically becomes visible after 4-6 weeks of consistent calorie deficit. Others may notice changes in your appearance after 8-12 weeks. Remember, the scales don't tell the whole story - body measurements and how your clothes fit are often better indicators of progress. Taking progress photos monthly can help you see changes you might miss day-to-day.

Free Calorie Deficit Calculator UK

Q: What is a calorie deficit?

A calorie deficit occurs when you consume fewer calories than your body burns. To lose weight, you need to create a consistent calorie deficit. For example, if your body burns 2,000 calories per day but you only eat 1,500 calories, you have a 500 calorie deficit. Over time, this deficit forces your body to use stored fat for energy, resulting in weight loss.

Calculate Your Calorie Deficit

Enter your details to get personalised results

Gender

Male

Female

Age (years)

Height

Current Weight

Target Weight

Activity Level

Weekly Weight Loss Goal

The NHS recommends losing 0.5-1kg per week for safe, sustainable weight loss.

What is a Calorie Deficit?

Understanding the science behind weight loss

A calorie deficit occurs when you consume fewer calories than your body burns throughout the day. This forces your body to use stored energy (primarily body fat) to make up the difference, resulting in weight loss over time.

The Simple Equation:

Calories In–Calories Out=Calorie Balance

• Negative balance (deficit) = Weight loss
• Zero balance (maintenance) = Weight stays the same
• Positive balance (surplus) = Weight gain

Key Concepts You Need to Know:

BMR (Basal Metabolic Rate)

The calories your body burns at rest just to stay alive - breathing, circulating blood, maintaining body temperature. This typically accounts for 60-75% of your daily calorie burn.

TDEE (Total Daily Energy Expenditure)

Your total daily calorie burn including all activity - exercise, walking, even digesting food. This is what you should base your calorie target on, not your BMR.

The 7,700 Calorie Rule

Approximately 7,700 calories of energy is stored in 1kg of body fat. To lose 0.5kg per week, you need a weekly deficit of about 3,850 calories (550 per day).

NHS Recommendation: For safe and sustainable weight loss, the NHS recommends losing 0.5 to 1kg per week by reducing your daily intake by 500-600 calories below your TDEE. Learn more at the NHS Better Health website.

How to Use This Calculator

Follow these simple steps to calculate your calorie deficit

1
Enter Your Personal Details
Select your gender and enter your age. These factors affect your metabolic rate.
2
Input Your Body Measurements
Enter your current height and weight. You can switch between metric (cm/kg) and imperial (feet/stone) units.
3
Set Your Target Weight
Enter your goal weight. This should be a realistic target based on healthy BMI ranges.
4
Select Your Activity Level
Choose how active you are on a typical day. Be honest - overestimating activity is a common mistake.
5
Choose Your Weight Loss Rate
Select how quickly you want to lose weight. The NHS recommends 0.5-1kg per week for sustainable results.
6
Get Your Personalised Results
Click calculate to see your daily calorie target, macros, and a timeline showing when you'll reach your goal.

Pro Tip: Your results are automatically saved to your browser, so you can return anytime to recalculate or track your progress without re-entering your details.

Weight Loss Tips & Best Practices

Weight Loss Tips

Evidence-based tips to support your calorie deficit journey

Stay Hydrated

Drink 6-8 glasses of water daily. Sometimes thirst is mistaken for hunger. Drinking water before meals can help reduce calorie intake.

Prioritise Protein

Aim for 1.6-2.2g of protein per kg body weight. Protein keeps you fuller longer and helps preserve muscle mass during weight loss.

Get Quality Sleep

Poor sleep increases hunger hormones and cravings. Aim for 7-9 hours per night to support your weight loss efforts.

Include Strength Training

Resistance exercise helps maintain muscle mass in a deficit. Aim for 2-3 sessions per week targeting all major muscle groups.

Manage Stress

Chronic stress raises cortisol, which can increase appetite and promote fat storage. Practice relaxation techniques like deep breathing or meditation.

Be Patient & Consistent

Sustainable weight loss takes time. Focus on consistency over perfection. Small daily habits compound into significant results.

For more evidence-based advice on healthy eating and weight loss, visit the British Nutrition Foundation.

DO
Best Practices

✓Eat plenty of vegetables with each meal for volume and nutrients
✓Track your food intake, at least initially, to build awareness
✓Plan your meals in advance to avoid impulsive eating
✓Choose whole, minimally processed foods most of the time
✓Allow yourself occasional treats - restriction often leads to binges
✓Weigh yourself at the same time weekly for accurate tracking
✓Take progress photos monthly to see visual changes
✓Celebrate non-scale victories like energy levels and fitness

DON'T
Common Mistakes

✗Don't skip meals - this often leads to overeating later
✗Don't cut calories too drastically - aim for a moderate deficit
✗Don't eliminate entire food groups without medical reason
✗Don't rely on the scale alone - it fluctuates daily
✗Don't compare your progress to others
✗Don't expect linear weight loss - plateaus are normal
✗Don't use exercise to 'earn' food or punish yourself
✗Don't give up after a bad day - get back on track at the next meal

Medical Disclaimer

This calculator provides estimates based on the Mifflin-St Jeor equation and should not replace professional medical advice. If you have underlying health conditions, are pregnant, breastfeeding, or have a history of eating disorders, please consult your GP or a registered dietitian before starting a weight loss programme. For professional guidance, visit the NHS obesity guidance.

Recommended Tools for Success

These tools can help you accurately track your calorie intake

Essential

Digital Kitchen Scale

Accurate food weighing is essential for tracking calories. A good digital scale measures in grams for precision.

View kitchen scales on Amazon

Helpful

Food Portion Containers

Pre-portioned containers make meal prep easier and help with consistent portion control throughout the week.

View portion containers on Amazon

Optional

Calorie Counting Book

A comprehensive calorie reference guide for when you're away from your phone or prefer offline tracking.

View calorie guides on Amazon

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Frequently Asked Questions

Everything you need to know about calorie deficits and weight loss