Macro Calculator

What this tool does

The Macro Calculator estimates your calorie needs from Mifflin-St Jeor and your goal, or uses your own target, and splits it into protein, carbohydrate and fat grams with preset or custom percentages. It shows per-meal amounts, protein in g/kg and a fibre target, and flags splits that fall outside common guidance.

Calories decide whether you gain or lose weight, but the macronutrients that make up those calories shape how you feel, perform and recover. Enough protein preserves muscle in a deficit, carbohydrate fuels hard training and fat supports hormones and vitamin absorption. Converting percentages into grams is where most people get stuck, because each macro carries a different energy density.

This calculator first estimates total daily energy expenditure with Mifflin-St Jeor and your activity level, then adjusts it for your goal (for example −20 percent to lose fat or +10 percent for a lean gain). You can also type your own calorie target. The chosen split is converted with 4 kcal per gram for protein and carbohydrate and 9 kcal per gram for fat, and the result is divided across your meals. A fibre target of 14 g per 1,000 kcal follows the US Dietary Guidelines.

How to use Macro Calculator

1. Enter units, sex, age, weight and height, and choose your activity level.
2. Select a goal, or switch on "Use my own calorie target" and type a number.
3. Pick a macro split preset, or choose Custom percentages and enter protein, carbs and fat (they must add up to 100).
4. Set how many meals you eat per day.
5. Read daily grams for each macro and the per-meal amounts in the result cards.
6. Check the chart and table, including protein in g/kg, and download the table for your food log.

Tips for better results

• Set protein first (often 1.6 to 2.2 g/kg when training), then split the remaining calories between carbs and fat to taste.
• Endurance athletes usually perform better with higher carbohydrate splits; a ketogenic split suits some people but impairs high-intensity work for others.
• Hit your weekly average rather than chasing exact grams every single day.

Common use cases

• Setting up a food-tracking app with daily macro goals.
• Planning a high-protein cutting phase without losing strength.
• Comparing how a keto or low-fat split changes grams per meal.
• Meal-prepping portions that match a coach's percentage plan.

Common mistakes to avoid

• Letting fat drop below about 20 percent of calories for long periods.
• Forgetting that alcohol contributes 7 kcal per gram outside the three macros.
• Using percentages alone on a very low calorie target, which can leave protein too low in grams.
• Re-entering an inflated activity level after already adding exercise calories elsewhere.