A calorie deficit occurs when you consume fewer calories than your body burns. It is the fundamental mechanism behind all weight loss — regardless of diet type. This calculator takes your Total Daily Energy Expenditure (TDEE) and your target weight loss rate, and gives you a daily calorie target to aim for.
Not sure of your TDEE? Use our Daily Calorie Needs Calculator first, then come back here with your result.
🧮 Calculate Your Calorie Deficit
📊 Your Daily Calorie Targets
Deficit size relative to maintenance (max shown: 30%)
💡 What This Means in Practice
📖 How a Calorie Deficit Works
The 3,500 Calorie Rule
One pound of body fat stores approximately 3,500 calories of energy. To lose one pound per week you need to create a deficit of 3,500 calories over seven days — or 500 calories per day. This is the most widely cited figure in weight loss science and underpins this calculator.
In practice, weight loss is not perfectly linear. The body adapts to reduced intake by lowering metabolism slightly over time, meaning actual results may be slightly slower than predicted. However the 3,500 calorie rule remains a reliable planning tool for most people.
Choosing the Right Deficit Size
0.5 lb per week (250 cal/day deficit) — The most sustainable approach. Small enough that most people don't feel significantly restricted. Best for people who want to make a gradual, lasting change or who have less than 10 lbs to lose.
1 lb per week (500 cal/day deficit) — The most commonly recommended rate. Meaningful enough to see progress, modest enough to be sustainable for most people. Generally considered the sweet spot.
1.5 lbs per week (750 cal/day deficit) — Appropriate for people with more weight to lose. Requires more dietary discipline. Still within the range considered safe without medical supervision for most healthy adults.
2 lbs per week (1,000 cal/day deficit) — The maximum generally recommended without medical supervision. Should only be attempted by people with significant weight to lose. At this rate, preserving muscle mass through adequate protein and resistance training becomes particularly important.
Deficit vs Exercise
A calorie deficit can be achieved through eating less, exercising more, or a combination of both. Research consistently shows that combining moderate dietary restriction with regular exercise produces better long-term results than either approach alone. Use our Calories Burned Calculator to see how exercise contributes to your daily deficit.
What to Eat on a Deficit
The distribution of your calories matters. Prioritising protein (at least 0.7g per pound of body weight) helps preserve muscle mass during weight loss. Use our Protein Intake Calculator to find your daily protein target, and our Macro Calculator to plan your full macro split. Log your daily food intake with our Food Tracker to stay within your calorie target.
❓ Frequently Asked Questions
A calorie deficit means consuming fewer calories than your body burns. When your intake is below your total daily energy expenditure (TDEE), your body uses stored fat to make up the difference, resulting in weight loss.
A deficit of approximately 3,500 calories over time produces one pound of fat loss. This figure is approximate — actual results vary based on metabolic adaptation, body composition changes, and water weight fluctuations.
A deficit of 500 calories per day (producing about 1 pound per week of weight loss) is the most commonly recommended rate. Smaller deficits of 250 calories per day are more sustainable for people with less to lose.
Larger deficits of 750-1,000 calories per day are appropriate for people with significant weight to lose but require more discipline and careful attention to protein intake to preserve muscle mass.
The most common reason is underestimating calorie intake. Studies show people typically underestimate their food intake by 20-40%, often by missing oils, dressings, drinks, or grazing.
Other reasons include overestimating exercise calorie burn, water retention from sodium or hormonal changes, and metabolic adaptation over time. Track intake precisely for 1-2 weeks to rule out underestimation before adjusting your target.
Rates above 2 pounds per week typically result in losing muscle mass along with fat, especially without resistance training and adequate protein. Very rapid weight loss is also associated with higher rates of regain, gallstones, and nutritional deficiencies.
Most health authorities recommend not exceeding 1-2 pounds per week without medical supervision. The exception is the early weeks of weight loss when significant water weight loss can produce faster initial results.
Both work, but research consistently shows that combining moderate dietary restriction with regular exercise produces better long-term results than either approach alone.
Diet is more efficient per minute spent (eating less takes no time; exercising takes hours), but exercise preserves muscle, improves cardiovascular health, and offsets metabolic adaptation. A typical approach is 75% of the deficit from diet and 25% from added activity.
Yes, but typically less than people fear. Metabolic adaptation reduces calorie burn by approximately 10-15% beyond what is explained by weight loss alone. This is real but manageable.
Adequate protein, resistance training, and avoiding extremely aggressive deficits minimise the slowdown. Periodic diet breaks (eating at maintenance for 1-2 weeks) can also help reset metabolic adaptation during longer cuts.
Most people can sustain a moderate deficit (500 calories per day or less) for 3-6 months before needing a diet break. Aggressive deficits should be limited to 4-8 weeks at a time.
Continuous deficits beyond these timeframes lead to increased metabolic adaptation, hormonal disruption, and adherence breakdown. Plan diet breaks at maintenance every 8-12 weeks during longer fat loss phases.
Focus on high-protein, high-fibre, whole foods that satisfy hunger for fewer calories. Adequate protein (0.7-1g per pound of bodyweight) preserves muscle mass during weight loss.
Fibre-rich vegetables and fruits add volume and nutrients with few calories. Avoid the trap of eating low-calorie but unsatisfying foods that leave you constantly hungry — sustainability matters more than perfection.
Hitting your deficit daily is what matters. Our AI tracker reads your meal description ("eggs, toast, avocado") and instantly logs the calories — no database searching, no scale required. 100% free.
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