Mifflin-St Jeor

Macros

Macro Calculator

Turn your calorie needs into daily macros — protein, carbohydrate and fat in grams. The calorie base comes from the Mifflin-St Jeor equation; the results show your split at maintenance and around your goals.

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What are macros?

Macros — short for macronutrients — are the three things calories come from: protein, carbohydrate and fat. Protein and carbs carry about 4 calories per gram, fat about 9. Tracking macros rather than just calories helps make sure enough of your intake is protein.

What macro split should I use?

A balanced macro split is 30% protein, 40% carbohydrate and 30% fat of daily calories — converted to grams at 4 kcal/g for protein and carbs and 9 kcal/g for fat. That is this calculator's default; once calories and protein are set, the carb–fat balance is mostly preference. For a protein-first target see the protein calculator.

A worked example

At a 2,500-calorie day on the default 30/40/30 split:

2,500 kcal at 30% protein / 40% carbs / 30% fat
MacroShareCaloriesGrams
Protein30%750 kcal188 g
Carbohydrate40%1,000 kcal250 g
Fat30%750 kcal83 g

Where the calories come from

The macro grams are built on your calorie figure, which is your TDEE from the Mifflin-St Jeor equation. To set macros for fat loss, work out your deficit first, then apply the split.

Sources

  1. Food and Agriculture Organization of the United Nations. Food energy — methods of analysis and conversion factors (Atwater general factors: protein 4, carbohydrate 4, fat 9 kcal/g). FAO Food and Nutrition Paper 77, 2003. FAO
  2. Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength. Br J Sports Med. 2018;52(6):376–384. PubMed

Common questions

How do I calculate my macros?

Start from your daily calories, then split them between protein, carbohydrate and fat. This calculator uses a balanced 30% protein / 40% carbs / 30% fat split by default, converting each share into grams (protein and carbs at 4 calories per gram, fat at 9).

What macros should I eat to lose weight?

Set your calories from your deficit target first, then keep protein high to protect muscle — often around 2 g per kg of body weight — and divide the rest between carbs and fat to taste. The split matters less than hitting your calories and protein.

What macros should I eat to build muscle?

Keep protein at roughly 1.6–2.2 g per kg of body weight (the same evidence-based range as the protein calculator), set calories at a modest surplus above your TDEE, and let carbohydrate take most of the remainder to fuel training. As with fat loss, the exact carb–fat balance matters less than hitting calories and protein.

Is a 40/30/30 split good?

It is a reasonable, balanced starting point, as is 30/40/30. There is no single best ratio — once calories and protein are set, carbs and fat are largely a matter of preference and what keeps you full and training well.