Plan your weight loss timeline with a daily calorie target
A calorie deficit occurs when you consume fewer calories than your body burns, forcing it to use stored energy (primarily body fat) to make up the difference. This is the fundamental mechanism behind all weight loss, regardless of the specific diet you follow. Whether you eat low-carb, low-fat, or a balanced diet, weight loss ultimately comes down to consistently maintaining a calorie deficit over time. The key to sustainable weight loss is choosing a deficit that is large enough to produce meaningful results but small enough to avoid excessive hunger, muscle loss, and metabolic adaptation. The NHS recommends a safe rate of weight loss of 0.5 to 1 kg per week for most adults. Extremely aggressive deficits (more than 1 kg per week) can lead to muscle loss, nutritional deficiencies, fatigue, and a phenomenon known as metabolic adaptation, where your body reduces its energy expenditure in response to prolonged severe restriction. This calculator takes your current weight, target weight, TDEE (Total Daily Energy Expenditure), and preferred rate of loss, then calculates your daily calorie target and estimates how long it will take to reach your goal. It gives you a concrete timeline so you can set realistic expectations and stay motivated.
To plan your calorie deficit: 1. Enter your current weight in kilograms. Weigh yourself first thing in the morning for the most consistent reading. 2. Enter your target weight. Set a realistic goal -- the NHS suggests that losing 5-10% of your body weight can produce significant health benefits even if you do not reach your "ideal" weight. 3. Enter your daily calorie expenditure (TDEE). If you do not know your TDEE, use the TDEE Calculator on this site first. Your TDEE is the number of calories you burn per day including activity. 4. Select your weekly loss rate. Slower rates (0.25-0.5 kg per week) are more sustainable and preserve more muscle mass. Faster rates (0.75-1.0 kg per week) produce quicker results but require a larger daily deficit and more discipline. 5. View your results. The calculator shows your daily calorie target, the size of the daily deficit, the number of weeks to reach your goal, and an estimated target date. The chart helps you visualise the energy split between intake and deficit.
The calorie deficit calculation is based on the widely accepted energy balance principle and the approximation that 1 kg of body fat contains approximately 7,700 calories of stored energy. To lose a specific amount of weight per week, the required daily deficit is: daily deficit = (weekly loss in kg x 7,700) / 7. For example, to lose 0.5 kg per week: daily deficit = (0.5 x 7,700) / 7 = 550 kcal per day. To lose 1.0 kg per week: daily deficit = (1.0 x 7,700) / 7 = 1,100 kcal per day. Your daily calorie target is then: daily calories = TDEE - daily deficit. If your TDEE is 2,200 kcal and you want to lose 0.5 kg per week, your daily target is 2,200 - 550 = 1,650 kcal. The time to reach your goal is: weeks = (current weight - target weight) / weekly loss rate. If you weigh 85 kg and target 75 kg at 0.5 kg per week, that is 10 / 0.5 = 20 weeks. The target date is calculated by adding the number of weeks to today's date. It is important to note that this is a linear estimate. In practice, weight loss is rarely linear -- you will experience fluctuations due to water retention, hormonal cycles, and changes in body composition. The calculator also does not account for metabolic adaptation, which may slow progress over time and require periodic reassessment of your TDEE and deficit.
The NHS recommends that women should not go below 1,200 kcal per day and men should not go below 1,500 kcal per day without medical supervision. If your calculated target falls below these levels, consider a slower rate of loss or increasing your TDEE through more activity. If you have a history of disordered eating or any medical conditions, consult your GP before starting a calorie-restricted diet.