Macro Calculator

Macro Calculator

A "macro" is short for macronutrient - the three nutrients that make up almost all of the calories you eat: protein, carbohydrates, and fat. Hitting a calorie target alone doesn't tell you whether those calories are building muscle, fuelling workouts, or just adding fat. This calculator turns your body stats, activity level, and goal into a concrete daily target in grams for each macro, so you know not just how much to eat, but what to eat it as.

How it works

The calculation happens in three stages.

1. Basal Metabolic Rate (BMR)

BMR is the energy your body burns at complete rest just to stay alive - breathing, circulating blood, maintaining body temperature. This calculator uses the Mifflin-St Jeor equation, widely considered the most accurate BMR formula for the general population:

$$BMR_{male} = 10 \times weight_{kg} + 6.25 \times height_{cm} - 5 \times age + 5$$ $$BMR_{female} = 10 \times weight_{kg} + 6.25 \times height_{cm} - 5 \times age - 161$$

2. Total Daily Energy Expenditure (TDEE)

BMR is then scaled up by an activity multiplier to estimate how many calories you actually burn in a full day, including movement and exercise:

Activity level	Multiplier
Sedentary (little or no exercise)	1.2
Lightly active (light exercise 1-3 days/week)	1.375
Moderately active (moderate exercise 3-5 days/week)	1.55
Very active (hard exercise 6-7 days/week)	1.725
Extremely active (hard daily exercise + physical job)	1.9

$$TDEE = BMR \times activityMultiplier$$

3. Goal-adjusted calories and macro split

Your goal shifts TDEE up or down:

• Lose weight: 80% of TDEE (a ~20% deficit)
• Maintain weight: 100% of TDEE
• Gain weight: 115% of TDEE (a ~15% surplus)

That target calorie figure is then split into grams of protein, carbs, and fat according to your chosen diet style, using the fact that protein and carbs supply 4 calories per gram while fat supplies 9 calories per gram:

$$grams = \frac{targetCalories \times macroPercent}{caloriesPerGram}$$

Diet style	Protein	Carbs	Fat
Balanced	30%	40%	30%
High Protein	40%	30%	30%
Low Carb	35%	20%	45%
Keto	25%	5%	70%

Worked example

A 30-year-old male weighing 80 kg, 178 cm tall, moderately active, aiming to lose weight on a balanced diet:

1. BMR = 10 x 80 + 6.25 x 178 - 5 x 30 + 5 = 1,777.5 calories/day
2. TDEE = 1,777.5 x 1.55 ≈ 2,755 calories/day
3. Target calories (lose, 80%) ≈ 2,204 calories/day
4. Protein (30%): 2,204 x 0.30 / 4 ≈ 165 g
5. Carbs (40%): 2,204 x 0.40 / 4 ≈ 220 g
6. Fat (30%): 2,204 x 0.30 / 9 ≈ 73 g

How to use this calculator

1. Enter your weight, height, and age.
2. Select your biological sex (used by the BMR formula).
3. Select your activity level and weight goal.
4. Choose a diet style - Balanced works well for most people; High Protein suits strength training; Low Carb and Keto suit specific dietary approaches.
5. Submit to see your daily calorie target and the exact grams of protein, carbs, and fat to aim for each day.

A note on accuracy

This tool gives a standard, formula-based estimate for a healthy adult - it is not personalised medical or dietary advice. Individual metabolism, medical conditions, and training history can shift real requirements. If you have a medical condition, are pregnant, or are training for a competitive event, check your plan with a doctor or registered dietitian before following it strictly.