"Eat less, exercise more" is the most common weight loss advice, but it's worthless without a number. How many calories are "less"? A sedentary 70kg person burns roughly 1,700 calories per day at rest (doing nothing), plus 300-500 from daily movement, totaling ~2,000-2,200 maintenance calories. To lose weight, they might eat 1,500 calories (500 calorie deficit), targeting roughly 0.5kg loss per week. But if they're very active (gym 5x/week), their maintenance might be 2,800 calories, and the same 1,500-calorie diet would be dangerously low. Without knowing your personal maintenance calorie number, any diet advice is guesswork. You can't optimize what you don't measure.",
"This calorie calculator does the math for you. It calculates your BMR (Basal Metabolic Rate—calories burned at rest) using the Mifflin-St Jeor equation, then multiplies by your activity level to get TDEE (Total Daily Energy Expenditure—your true maintenance calories). From there, weight loss becomes arithmetic: eat 500 calories below TDEE for roughly 0.5kg loss/week, eat 250 below for 0.25kg/week (slower, more sustainable), or eat above for weight gain. The calculator shows all three scenarios instantly. Whether you're trying to lose weight, maintain, or build muscle, you now have a scientific starting point instead of guessing.",
The disclaimer: these are estimates, not prophecies. Your actual calorie burn varies based on body composition, genetics, metabolism, and how accurately you measure food intake. But they're well-validated estimates (the Mifflin-St Jeor equation is used by nutritionists worldwide) and they give you a starting point to test and adjust based on real results. Track your food intake honestly for 2-3 weeks, compare actual weight change to predictions, and adjust calories up or down slightly if needed.
How daily calorie needs are estimated
First the calculator finds your BMR (resting calorie burn) with the
Mifflin-St Jeor equation, then multiplies it by an activity factor to
get your maintenance calories (TDEE). Goal targets simply add or subtract a calorie
adjustment from that maintenance figure. BMR varies significantly by age, sex, height, and weight: a 25-year-old male at 180cm and 80kg burns roughly 1,800 calories at rest, while a 50-year-old female at 160cm and 65kg burns about 1,300 calories. That 500-calorie difference is pure biology—muscle tissue burns more calories even when sleeping.
Activity level and its impact on calorie burn
Your BMR is just baseline—add activity and it increases significantly. A sedentary person (office job, minimal exercise) has a 1.2x activity multiplier. Someone exercising 3-4 days/week uses 1.55x. An athlete training hard 5-6 days/week uses 1.725x. The difference is enormous: a 1,700 BMR becomes 2,040 calories (sedentary) vs. 2,933 calories (athlete). These same people eating the same amount gain or lose weight at completely different rates. The calculator accounts for this by asking about your activity level and adjusting accordingly.
Weight loss strategies: deficits and sustainability
A 500 calorie daily deficit means losing roughly 0.5kg per week, accumulating 2kg per month (realistic and sustainable for most people). A 1,000 calorie deficit loses 1kg weekly but feels extreme: if your maintenance is 2,000 calories, eating 1,000 is psychologically hard and physically unsustainable long-term. Moderate deficits (250-500 calories) are better because you're less hungry, keep more strength/energy, and have higher completion rates. The calculator lets you explore these trade-offs: slower loss (250/day deficit = 0.25kg/week) versus faster (500/day = 0.5kg/week) and helps you choose based on lifestyle. Most successful dieters find a deficit they can sustain for 3-6 months rather than a severe deficit they quit after 2 weeks.
years
cm
kg
Daily calories to maintain weight
2,633 kcal/day
Mild weight loss (~0.25 kg/week)
2,383
Weight loss (~0.5 kg/week)
2,133
Maintain weight
2,633
Mild weight gain (~0.25 kg/week)
2,883
Weight gain (~0.5 kg/week)
3,133
Using the goal targets
Lose weight — eat below maintenance (a moderate deficit).
Maintain — eat at maintenance.
Gain weight — eat above maintenance (a moderate surplus).
Frequently asked questions
How many calories do I need per day?
Your maintenance calories equal your BMR multiplied by an activity factor. Eat around that number to maintain weight, fewer to lose, and more to gain.
How big should a calorie deficit be?
A deficit of about 500 calories a day is a common, sustainable target for roughly half a kilogram (about one pound) of weight loss per week. Very aggressive deficits are harder to maintain and may not be healthy.
Are these numbers exact?
They are well-validated estimates. Real needs vary with body composition, genetics and daily movement, so adjust based on how your weight actually changes over a few weeks.
Should I eat below my BMR?
Generally it is not recommended to eat below your BMR for long periods. For personalised guidance, especially with health conditions, consult a doctor or dietitian.
For general information only — not medical advice.
