Macro Calculator

Counting total calories tells you how much to eat, but not what to eat. This macro calculator takes the calorie-counting one step further: it estimates your daily energy needs and then divides your target calories into grams of the three macronutrients that make up every food label — protein, carbohydrate and fat. That way you can plan meals or set targets in a food-tracking app rather than guessing.

It works in three moves. First it estimates your Basal Metabolic Rate (BMR) — the energy your body burns at complete rest — with the Mifflin-St Jeor equation. Then it scales that up by an activity multiplier to give your Total Daily Energy Expenditure (TDEE). Finally it applies your chosen calorie adjustment (a deficit to lose, maintenance, or a surplus to gain) and splits the result into grams. If you only want the calorie side of that story, the TDEE calculator and the BMR calculator cover those steps in isolation.

A calorie target alone doesn’t tell you what to put on your plate. Structured macro targets give food tracking a concrete daily checklist — hit your protein gram number, fill the rest with carbs and fat — which is why many nutrition coaches and tracking apps build their guidance around grams rather than a single calorie count.

The engine runs these steps in order:

BMR (male) = 10 × kg + 6.25 × cm − 5 × age + 5
BMR (female) = 10 × kg + 6.25 × cm − 5 × age − 161
TDEE = BMR × activity multiplier (1.2 to 1.9)
Goal calories = TDEE + your adjustment (floored at a safe minimum)
Protein g = goal kcal × protein% ÷ 4
Carb g = goal kcal × carb% ÷ 4
Fat g = goal kcal × fat% ÷ 9

The divisors 4, 4 and 9 are the Atwater general factors — the standard energy densities used on nutrition labels: protein and carbohydrate each yield about 4 kcal per gram, while fat is more than twice as energy-dense at 9 kcal per gram. That is why a “30% fat” split produces far fewer grams than a “30% carb” split from the same calories.

A 30-year-old man, 70 kg and 175 cm, moderately active, eating at maintenance with a 30% protein / 40% carb / 30% fat split. His BMR is about 1,649 kcal, his TDEE about 2,556 kcal, and those calories break down as follows (generated live by the same engine that powers the calculator, so the numbers can never drift from the tool):

There is no single “correct” split — the National Academies publish ranges (the Acceptable Macronutrient Distribution Ranges) rather than fixed targets. The table below shows where common approaches sit inside those ranges. Whichever you pick, the three shares must add up to 100% so the grams reconstitute your calorie goal.

A per-body-weight protein target (roughly 1.6-2.2 g/kg for people who train) is often a better anchor than a flat percentage. Once you know your calorie goal from the calorie calculator, set your protein first, then divide the rest between carbs and fat to taste.

• BMR uses Mifflin-St Jeor, the most accurate common predictive equation for healthy adults, but any predictive formula carries roughly ±10% error versus measured resting energy expenditure. Body composition, medications and health conditions all shift the real figure. Some calculators instead use the Katch-McArdle formula, which factors in lean body mass and can be more accurate for people who know their body-fat percentage; this tool uses Mifflin-St Jeor because it only needs age, weight, height and sex.
• TDEE is BMR times a single activity multiplier; it does not separately model deliberate exercise and everyday movement (NEAT), so an unusually active or sedentary lifestyle may need a manual calorie tweak.
• The percentage split is a convention, not a medical prescription. Protein needs are often better expressed per kilogram of body weight than as a flat percentage of calories.
• The −500 kcal ≈ 0.45 kg/week rule is a linear approximation; real weight change slows as your body adapts.
• Grams use the three-macronutrient Atwater model and are rounded to the nearest gram for display. Fiber, alcohol and sugar alcohols are not modeled separately. Mifflin-St Jeor is validated for adults, not children, adolescents, or pregnant/lactating women.