In short: Every diet on the internet eventually comes back to one number: how many calories your body actually burns in a day. Eat far under it and you crash; eat far over it and you gain. The problem is that generic advice like 2,000 calories ignores your weight, height, age, sex and how much you move.
Updated August 28, 2026, after a fresh review, with updated visuals and links.
This calculator uses the Mifflin-St Jeor equation, the one the Academy of Nutrition and Dietetics rates as the most accurate for most people, and then splits your target into protein, carbs and fat so the number is usable in the kitchen, not just on paper.
How to read your results
First comes your BMR, the calories you burn in bed all day. A 30-year-old, 70 kg, 170 cm woman sits near 1,445 kcal before lifting a finger. That floor matters because eating below it for weeks is what triggers the tiredness and rebound eating people blame on willpower.
Second is your maintenance calories (TDEE): BMR multiplied by your real activity. The difference between sedentary and lightly active is roughly 300 kcal a day, which is why an honest activity pick matters more than a flattering one.
Finally you get two working targets: about 500 kcal under maintenance for steady weight loss (close to 0.5 kg a week) and 300 kcal over for controlled gain, each converted into grams of protein, carbs and fat with a 30/35/35 split. With 1,800 kcal, that is about 135 g protein, 158 g carbs and 70 g fat per day.
Worth remembering
- Weigh yourself three mornings a week and compare weekly averages, not single days. Water swings hide real fat loss for days at a time.
- If after three weeks the average has not moved, adjust by 100-200 kcal, never by slashing in half. Small corrections survive; big ones get abandoned.
Frequently asked
How accurate is the Mifflin-St Jeor equation?
For most adults it lands within about 10 percent of lab-measured expenditure. Very muscular or very high body fat profiles drift a bit more, which is why the real calibration is your scale trend over three weeks.
Should I eat back the calories my watch says I burned?
Usually no. Fitness watches overestimate workout burn by 20 to 50 percent. Your activity multiplier already accounts for regular training, so eating back watch calories double-counts the exercise.
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