Weight loss is, at its core, an energy balance problem.
About this calculator
Weight loss is, at its core, an energy balance problem. Burn more calories than you eat, and your body dips into fat stores to make up the difference. This calculator estimates how many calories you should eat daily to lose weight at your chosen pace, and how long the whole process will take.
It uses the Mifflin-St Jeor equation for BMR (the most accurate widely-used formula, validated in a 2005 meta-analysis of 36 studies) and multiplies by an activity factor to get your Total Daily Energy Expenditure. The deficit is calculated from the fact that 1 kg of body fat stores approximately 7,700 kcal of energy.
Safe loss rates are 0.5-1 kg per week. Faster than that and you risk muscle loss, nutrient deficiencies, gallstones, and metabolic adaptation where your body lowers its TDEE in response. The calculator warns you if the required calorie intake drops below safe minimums (1,500 kcal for men, 1,200 for women).
For a more detailed macro breakdown (protein, carbs, fat), use the [[macro]] calculator. To understand your maintenance calories in more detail, see the [[tdee]] calculator. To track body composition changes, pair with the [[body-fat]] or [[bmi]] calculator.
Common uses
- 30-year-old software engineer (80 kg, 175 cm) wanting to reach 72 kg before a wedding in 6 months
- Post-pregnancy weight loss plan targeting 0.5 kg/week while breastfeeding
- Person with BMI 28 aiming for normal BMI range, wondering how long it will realistically take
- Gym-goer at 90 kg wanting to cut to 82 kg for a summer trip while preserving muscle
- Checking whether losing 15 kg in 3 months is safe or dangerously aggressive
- Comparing the calorie target difference between losing 0.5 vs 1 kg per week
Frequently asked questions
How accurate is this calculator?
The Mifflin-St Jeor equation predicts BMR within 10% for most people. Real-world calorie needs vary based on genetics, muscle mass, NEAT (fidgeting, walking), and hormonal factors. Use this as a starting point and adjust based on actual weekly weight trends after 2-3 weeks.
Is 0.5 kg/week a realistic rate?
Yes, 0.5 kg/week is considered safe and sustainable by most health organizations. It requires a daily deficit of about 550 calories, which is achievable through a combination of eating 300-400 fewer calories and adding 20-30 minutes of walking. People with more weight to lose can safely aim for 0.75-1 kg/week initially.
What happens if my calorie target goes below 1200/1500?
Eating below these minimums consistently risks nutrient deficiencies, muscle loss, fatigue, hair loss, and metabolic slowdown. If the calculator shows you need to eat below these levels, reduce your weekly loss rate target or add more exercise to increase TDEE instead.
Should I eat back exercise calories?
Partially. If your activity level selection already accounts for regular exercise, do not add more. If you do an extra unplanned workout, eating back 50% of those calories is a good rule of thumb. Fitness trackers overestimate exercise calories by 30-50%.
Why does weight loss slow down over time?
Two reasons: (1) as you lose weight, your BMR drops because a lighter body burns fewer calories, and (2) metabolic adaptation means your body becomes more efficient. Recalculate your targets every 5 kg lost. A person at 70 kg has a lower TDEE than at 80 kg, so the same diet that produced 0.5 kg/week loss initially may only produce 0.3 kg/week later.
Is it better to cut calories or exercise more?
For pure weight loss, cutting calories is more time-efficient. A 500-calorie deficit takes 5 minutes to achieve by skipping a snack but 60 minutes of running to achieve through exercise. However, exercise preserves muscle, improves mood, and builds the habit. The best approach combines both: eat 300 fewer calories and burn 200 more through movement.
What is the minimum safe calorie intake?
Generally 1,500 kcal/day for men and 1,200 kcal/day for women for moderate-duration diets. Very low calorie diets (800-1000 kcal) exist but should only be done under medical supervision and for limited periods. They carry real risks of gallstones, muscle loss, and nutrient deficiency.
Can I lose weight without tracking calories?
Yes. Calorie counting is one approach, not the only one. Portion control, eliminating liquid calories, eating more protein and fiber, intermittent fasting, and mindful eating all create deficits without explicit counting. This calculator gives you the target number so you know what range to aim for, even if you do not count daily.