Daily Calorie Deficit
Time to Goal
Estimated Goal Date
Table of Contents
How Long Will It Take to Lose Weight?
Weight loss comes down to one principle: burning more calories than you consume. But knowing exactly how long it will take to reach your goal weight — and how large a daily deficit you need — is where this calculator helps. Enter your current weight, target weight, and preferred weekly pace to get a clear timeline and daily calorie target.
How weight loss is calculated
One kilogram of body fat stores approximately 7,700 calories of energy. To lose that kilogram, your body needs to be in a cumulative calorie deficit of 7,700 calories. At a deficit of 550 calories per day — roughly 3,850 calories per week — you would lose approximately 0.5 kg per week.
This calculator works backwards from your chosen weekly rate to determine the daily deficit required: daily deficit = (weekly rate × 7,700) ÷ 7. Your timeline is then calculated as the total weight to lose divided by your weekly pace.
It is important to note that this is a mathematical estimate. Real-world weight loss is influenced by metabolic adaptation, water retention, hormones, and individual variation. The estimate is most accurate over longer periods and for people with moderate amounts of weight to lose.
Choosing the right pace
0.25 kg/week requires a daily deficit of just 275 calories. This is ideal for people close to their goal weight, those who prefer a very gradual approach, or athletes who cannot afford to cut calories more aggressively. It is the most sustainable option but the slowest.
0.5 kg/week requires approximately 550 calories per day. This is the most commonly recommended target — it is challenging enough to make meaningful progress but gentle enough to preserve muscle and avoid excessive hunger. Most people can achieve this through a combination of modest dietary changes and regular exercise.
0.75 kg/week requires roughly 825 calories per day. Achievable for most people, but requires consistent effort. At this rate, attention to food quality and protein intake becomes more important to avoid muscle loss.
1.0 kg/week requires approximately 1,100 calories per day. This is the upper limit recommended by most health authorities. It may be appropriate for people with a significant amount of weight to lose under medical supervision, but is difficult to sustain long-term without professional guidance.
How to create a calorie deficit
A calorie deficit can be created through three levers: eating less, moving more, or a combination of both. Research consistently shows that combining dietary changes with increased physical activity is more effective for long-term weight loss than either approach alone, because exercise preserves muscle mass and helps prevent metabolic adaptation.
Dietary changes are typically responsible for the majority of the deficit. Reducing portion sizes, cutting out high-calorie drinks, and prioritising filling foods (protein, fibre, vegetables) make it easier to sustain a deficit without feeling constantly hungry.
Exercise adds to the deficit and improves body composition. Cardiovascular exercise burns calories directly, while strength training preserves muscle mass and keeps your metabolism higher as you lose weight. Aim for a mix of both.
Use our Calorie Calculator to estimate your daily maintenance calories, then subtract the daily deficit shown above to find your target intake.
Why weight loss is not always linear
Most people experience faster weight loss in the first week or two — this is largely water weight, as the body depletes glycogen stores when calories are reduced. After this initial drop, progress typically slows to the rate predicted by your calorie deficit.
As you lose weight, your body needs fewer calories to function because there is less mass to maintain. This means the same deficit will produce slightly slower results over time. If your weight loss has stalled for several weeks, recalculate your maintenance calories using your current weight and adjust your intake or activity level accordingly.
Hormonal factors, sleep, stress, and medication can all affect both actual calorie burn and the body's tendency to retain water, causing fluctuations that can be frustrating on a day-to-day basis. Weighing yourself weekly rather than daily, and tracking the average trend over time, gives a more accurate picture of progress.
Setting a realistic goal
This calculator works best when the goal weight is realistic for your height and body type. Use the BMI Calculator or Body Fat Percentage Calculator to help identify a healthy target weight range. Losing weight to a point below a healthy BMI is counterproductive and carries its own health risks.
Once you have reached your goal, the challenge shifts from losing to maintaining. The habits that produced the loss — consistent exercise, attention to diet quality, and regular monitoring — are the same ones that make maintenance possible.
FAQs
Weight loss is calculated using the principle that one kilogram of body fat contains approximately 7,700 calories. To lose weight, you need a calorie deficit — burning more calories than you consume. The daily deficit required equals your chosen weekly loss rate multiplied by 7,700, divided by 7. For example, to lose 0.5 kg per week, you need a daily deficit of roughly 550 calories.
A safe and sustainable deficit is typically 500–750 calories per day, which supports a loss rate of 0.5–0.75 kg per week. Deficits larger than 1,000 calories per day are generally not recommended as they can cause muscle loss, nutritional deficiencies, and metabolic adaptation. For most people, a 500-calorie daily deficit is a good starting point.
Most health authorities, including the NHS and CDC, recommend a loss rate of 0.5 to 1 kg (1 to 2 lbs) per week as safe and sustainable. Faster rates tend to result in muscle loss, fatigue, and increased likelihood of regaining weight. Slower rates of 0.25 kg per week can also be effective for people close to their goal or who prefer a very gradual approach.
As you lose weight, your body requires fewer calories to function — your basal metabolic rate decreases because there is less mass to maintain. This means the same calorie deficit that produced quick initial results will gradually produce slower results. Recalculating your calorie needs every 5–10 kg of weight lost helps you stay on track.
Diet is generally more impactful for creating a calorie deficit because it is easier to cut 500 calories from your intake than to burn 500 extra calories through exercise. However, combining a moderate calorie reduction with regular exercise preserves muscle mass, improves metabolic health, and makes the deficit easier to maintain long-term. Neither approach alone is as effective as both together.
A calorie deficit occurs when you consume fewer calories than your body expends over a given period. Your body responds to this energy shortfall by drawing on stored fat for fuel, which results in weight loss over time. The size of the deficit determines how quickly weight is lost — a larger deficit means faster loss, but also greater risk of muscle loss and nutritional deficiency if sustained too aggressively.