Maintenance Calories
2,635kcal/day
Scenario
How Many Calories to Lose 1 kg Per Week — The Math
Learn exactly how many calories you need to cut to lose 1 kg per week. Based on the 7,700 kcal per kg rule, you need a 1,100 kcal daily deficit. Find your target.
Interactive Calculator
Your Details
kcal
kg
kg
kcal
Your Calorie Deficit Plan
Deficit Intake
2,135kcal/day
Daily Deficit
500kcal
Weekly Weight Loss
0.45kg/week
weeks
To lose 10 kg at 0.45 kg/week
12-Week Weight Projection
Linear estimate with approximate 95% prediction interval.
Deficit Rate Comparison
Weekly weight loss at different deficit levels. Highlighted = your selection.
Summary: Your maintenance calories are 2,635 kcal/day. With a daily deficit of 500 kcal, consume 2,135 kcal/day to lose approximately 0.45 kg per week, reaching your goal in about 22 weeks.
The formula
The formula
What Calorie Deficit Measures
A calorie deficit is the difference between the calories your body burns and the calories you consume. When you consume fewer calories than your body needs for maintenance, your body turns to stored energy — primarily body fat — to make up the shortfall. This is the fundamental principle behind all weight loss, regardless of the specific diet or approach you follow.
Creating a calorie deficit is not about starving yourself. It is about understanding your body's energy needs and finding a sustainable balance that allows gradual, steady fat loss while preserving muscle, energy, and overall health. The size of your deficit determines how quickly weight changes occur, and the quality of your nutrition during the deficit determines whether that weight change comes from fat or lean tissue.
The Calorie Deficit Formula
Maintenance = BMR × Activity Factor
Deficit Intake = Maintenance − Daily Deficit
Weight loss per week ≈ (Daily Deficit × 7) ÷ 7,700 kg
Weeks to goal = Total weight loss ÷ (Weekly loss) — or Total deficit ÷ Daily Deficit ÷ 7
Formula Source
The 7,700 kcal per kilogram of body fat approximation is widely used in clinical and research settings. It is derived from the energy density of adipose tissue and has been validated in controlled feeding studies. The underlying energy balance model — change in energy stores = energy in − energy out — is a fundamental principle of thermodynamics applied to human physiology.
Reference URL: https://doi.org/10.1016/j.ajcnut.2022.02.001
Last Verified: 2026-08-09
Worked Example
A 35-year-old woman with a BMR of 1,350 kcal and a moderately active lifestyle (activity factor 1.55) has a maintenance of approximately 2,093 kcal. To lose 0.5 kg per week, she needs a daily deficit of about 550 kcal, bringing her target intake to roughly 1,543 kcal/day. At this rate, she would lose approximately 5 kg in about 10 weeks. If she wanted a more modest pace of 0.25 kg per week, she would aim for a 275 kcal deficit and eat around 1,818 kcal/day, taking about 20 weeks to reach the same goal.
Calorie Deficit Reference Table
| Deficit Level | Daily Deficit | Weekly Loss (kg) | Weekly Loss (lb) |
|---|---|---|---|
| Mild | 250 kcal | ≈ 0.23 kg | ≈ 0.5 lb |
| Moderate | 500 kcal | ≈ 0.45 kg | ≈ 1.0 lb |
| Moderate-High | 750 kcal | ≈ 0.68 kg | ≈ 1.5 lb |
| Aggressive | 1,000 kcal | ≈ 0.91 kg | ≈ 2.0 lb |
Why Calorie Deficit Alone Is Not a Full Picture
While the calorie deficit is the mathematical foundation of weight loss, the body is not a simple furnace. Metabolic adaptation — sometimes called adaptive thermogenesis — means that when you reduce calorie intake, your body responds by slightly lowering its energy expenditure. This is an evolutionary survival mechanism. The result is that the actual rate of weight loss often slows after the first few weeks, even if you maintain the same deficit.
Hormones also play a major role. Prolonged calorie restriction can alter levels of leptin, ghrelin, cortisol, and thyroid hormones, which together influence hunger, satiety, and metabolic rate. The quality of the calories you eat matters as much as the quantity — sufficient protein, fiber, and micronutrients support a healthier metabolic response to the deficit.
Known Limitations
- The 7,700 kcal per kg rule is an approximation. Actual fat loss depends on individual body composition, dietary composition, and metabolic adaptations.
- BMR estimates from population formulas can be off by ±10 percent or more for individuals, especially at the extremes of body size or for people with high muscle mass.
- Activity factors are subjective. Your actual total daily energy expenditure depends on your specific movement patterns, occupation, and exercise habits.
- Does not account for the thermic effect of food, which varies by macronutrient composition and can affect the net deficit.
- Not suitable for individuals with eating disorders, metabolic conditions, or those who are pregnant, breastfeeding, or under medical supervision for weight-related conditions.
- Results are estimates only and should not replace personalized advice from a qualified healthcare provider.
Scenario guide
Scenario guide
The 7,700 kcal Rule
The widely used rule is that 1 kilogram of body fat stores approximately 7700 kcal of energy. This figure comes from the energy density of adipose tissue: pure fat contains 9 kcal per gram, but body fat is roughly 87 percent triglyceride plus water and connective tissue, giving an average energy density of about 7.7 kcal per gram. This rule is an approximation — actual energy content varies with individual body composition — but it is accurate enough for practical calorie targeting. Applied across a week, 7700 kcal ÷ 7 days = 1100 kcal per day. That is the daily calorie deficit required to lose roughly 1 kg of body fat per week.
Daily Deficit for 1 kg per Week
To create a 1100 kcal daily deficit, subtract 1100 from your TDEE. For a TDEE of 2500 kcal, your daily calorie target would be 1400 kcal. For a TDEE of 2200 kcal, the target would be 1100 kcal — which hits the absolute minimum floor for women. This illustrates why a 1 kg/week deficit is only appropriate for people with a sufficiently high TDEE: typically men over 90 kg, women over 75 kg, or anyone with a TDEE above roughly 2300 kcal. If your TDEE is lower, pursuing 1 kg per week pushes you below safe minimum intake and accelerates muscle loss. A deficit of 500 kcal per day (roughly 0.5 kg/week) is often the smarter choice.
Is 1 kg Per Week Realistic
- For higher starting weights: Yes. Individuals over 90 kg with high TDEEs can sustain a 1000 to 1100 kcal deficit without falling below safe intake floors. Rates of 1 kg/week are common in the first 4 to 8 weeks.
- For average body weights: Difficult. Most men below 80 kg and women below 65 kg have TDEEs that make a 1100 kcal deficit unsafe or unsustainable.
- For lean individuals: Not advisable. Lean individuals have less stored fat to draw on and a higher fraction of their body weight is metabolically active lean tissue. Rates above 0.5 kg/week in lean individuals accelerate muscle loss.
- Initial rapid loss is misleading: The first 1 to 2 weeks of a deficit often produce 2 to 3 kg of loss, but most of this is water and glycogen, not fat. Steady fat-loss rates settle near the deficit-based prediction after week 2 or 3.
How to Hit the Number
A 1100 kcal deficit can be achieved by eating less, moving more, or combining both — and combining both is usually more sustainable. For example, eating 500 kcal fewer than TDEE and burning an additional 600 kcal through exercise and increased daily activity produces the same 1100 kcal deficit without as drastic a drop in food intake. Prioritize the dietary component because self-reported exercise calories are often overestimated by 20 to 40 percent by wearable devices. Keep protein high (1.8 to 2.2 g/kg/day), resistance train to preserve muscle, and treat any exercise calories as conservative estimates. Track weight as a 7-day average, since the scale swings 0.5 to 2 kg daily due to hydration and sodium.
Adjusting When Progress Stalls
Even a perfectly executed 1 kg/week deficit will eventually stall. As body weight drops, TDEE falls, so the original 1100 kcal gap shrinks — a 1100 kcal deficit at 100 kg may be only 800 kcal at 80 kg on the same calorie target. Non-exercise activity typically drops subconsciously as the body conserves energy. If weekly average loss slows to below 0.5 kg for 2 consecutive weeks, take one of three actions: re-calculate TDEE at your new weight and restore the 1100 kcal gap, increase daily walking by 30 minutes, or reduce intake by 150 to 200 kcal. If loss exceeds 1.5 kg per week, slightly increase intake — too-rapid loss accelerates muscle loss and raises rebound-regain risk.
FAQ
Frequently Asked Questions
Based on the 7700 kcal per kg rule, losing 1 kg of body fat per week requires a daily deficit of approximately 1100 kcal (7700 ÷ 7 days). Subtract 1100 kcal from your TDEE to find your daily calorie target. For a TDEE of 2500 kcal, your target would be 1400 kcal per day. A 1100 kcal deficit is aggressive and is best suited to people with high starting weights and high TDEEs; most adults should aim for 0.5 kg per week instead (a 500 kcal daily deficit).
Losing 1 kg per week is achievable and generally safe for individuals with higher starting weights (men over 90 kg, women over 75 kg, or TDEEs above roughly 2300 kcal) when protein is high (1.8 to 2.2 g/kg/day) and strength training is maintained. It is not advisable for lean individuals or anyone whose TDEE would push them below 1200 kcal/day for women or 1500 kcal/day for men. Most adults achieve better long-term results at 0.5 to 0.75 kg per week, which better preserves lean mass and supports adherence.
The rule states that 1 kilogram of body fat stores approximately 7700 kcal of energy. This is derived from the energy density of adipose tissue: pure fat has 9 kcal per gram, but body fat is roughly 87 percent triglyceride plus water and connective tissue, averaging about 7.7 kcal per gram. To lose 1 kg per week, divide 7700 by 7 to get a required daily deficit of about 1100 kcal. The rule is an approximation but is accurate enough for practical calorie targeting.
In theory, a 1100 kcal deficit purely from exercise would require roughly 1.5 to 2 hours of moderate-to-vigorous exercise per day, which is unsustainable for most people. A combined approach is more practical: eat 500 to 700 kcal below TDEE and burn an additional 300 to 600 kcal through exercise and daily activity. Note that wearable devices typically overestimate exercise calories by 20 to 40 percent, so treat exercise calories as conservative estimates and rely more on dietary control for the deficit.
Stalls typically appear after 4 to 8 weeks because as you lose weight your TDEE drops, shrinking the effective deficit. If weekly average loss slows to below 0.5 kg for 2 consecutive weeks, re-calculate TDEE at your new weight and restore the 1100 kcal gap, add 30 minutes of daily walking, or reduce intake by 150 to 200 kcal. Avoid slashing further — dramatic cuts accelerate muscle loss and adaptation. If loss exceeds 1.5 kg per week, slightly increase intake to protect lean mass.
Keep going
Related calculators & guides
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Protein Calculator
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Meal Calorie Calculator
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