A 30-year-old man, 175 cm and 70 kg, moderately active and keeping his weight, needs about 2,556 kcal a day: 112 g of protein, 367 g of carbohydrate and 71 g of fat. To lose weight the same man would eat 2,056 kcal, with 140 g of protein.
What this calculates
Enter your age, sex, height, weight and activity level, and choose to lose, maintain or gain weight. This works out your BMR, your daily calories for the goal, and the grams of protein, carbohydrate and fat that make them up, with a table and a chart of where the calories come from.
The formula
Calories
TDEE = BMR × activity factor; goal = TDEE − 500 (lose), TDEE (maintain) or TDEE + 300 (gain)Protein
protein (g) = 2.0, 1.6 or 1.8 × weight in kgFat and carbohydrate
fat (g) = 25% × calories ÷ 9; carbs (g) = (calories − 4 × protein − 9 × fat) ÷ 4The BMR is Mifflin-St Jeor: 10 × kg + 6.25 × cm − 5 × age, plus 5 for men or minus 161 for women.
Worked example
To lose weight the calories become 2,056 with 140 g protein, 246 g carbs and 57 g fat. A woman who would fall below 1,200 kcal is held at 1,200.
When to use it, and the mistakes to avoid
Use it to set a starting target for a diet or a gain phase, to see how a goal changes the split, or to plan meals around protein.
The mistakes that cost the most:
- Following the numbers rigidly. They are estimates; adjust from your own results.
- Eating too little. Very low calories cost muscle and energy; the minimums exist for a reason.
- Forgetting protein. Hitting calories with little protein can cost muscle on a diet.
- Mis-setting activity. Overestimating it raises the calories too high.
- Treating it as medical advice. For a health condition, see a doctor or dietitian.
FAQ
What are macros?
Macronutrients: protein, carbohydrate and fat, the three nutrients that supply calories. Protein and carbohydrate give 4 kcal a gram and fat 9. Your daily calories set the total, and the macros say how to split it.
How much protein do I need?
This calculator uses 1.6 g per kilogram of body weight to maintain, 1.8 to gain and 2.0 to lose weight, where the extra helps protect muscle. For a 70 kg person that is 112 g, 126 g or 140 g. Needs vary, so treat these as a starting point.
How are the calories worked out?
From your BMR (Mifflin-St Jeor) times an activity factor, which gives the calories to keep your weight. Losing weight takes 500 off a day, about 0.5 kg a week, and gaining adds 300. A diet is never set below 1,500 kcal for men or 1,200 for women without supervision.
Why is fat 25% of the calories?
It sits in the middle of the commonly recommended 20% to 35% range, enough for hormones and absorbing vitamins while leaving room for carbohydrate. Carbohydrate is simply what is left once protein and fat are set.
Are the numbers exact?
No. Calorie needs can differ from the estimate by 10% or more, and the protein and fat shares are guidelines, not rules. Follow the plan for two to three weeks, track your weight, and adjust the calories up or down. This is not medical advice.