Macro Calculator

How this estimate is calculated

The calculation uses the Mifflin-St Jeor formula, a widely recognized method for estimating basal metabolic rate (energy spent at rest). This figure is then multiplied by an activity factor to get your total daily energy expenditure, then adjusted based on your goal (a modest deficit for gradual weight loss, a modest surplus for muscle gain).

The macronutrient split follows general principles: enough protein to support muscle recovery, fat for basic hormonal function, and carbs to cover the rest of your energy needs, particularly important for an athlete training regularly.

The formulas behind the calculation

The Mifflin-St Jeor formula estimates your basal metabolic rate (BMR), the energy you burn at rest:

• Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
• Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161

BMR is then multiplied by an activity factor: 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (high) or 1.9 (very high), then adjusted for your goal.

Two worked examples

These values correspond to weight maintenance. For weight loss or weight gain, the calculator applies a moderate adjustment: a gradual gap beats a crash diet when you are preparing for a race.

How much protein for a Hyrox athlete?

For endurance and strength athletes, the most commonly cited recommendations are around 1.4 to 2 g of protein per kilogram of body weight per day, depending on training volume and goal. Carbohydrates cover most of the remaining energy: they are your main fuel for running sessions and intense circuits. The calculator gives you a starting point that you then adjust based on your energy, your recovery and how your weight evolves.

Adjusting your intake around training and race day

• Before an intense session: a carbohydrate-rich, easy-to-digest meal or snack.
• After the session: protein and carbohydrates to support recovery.
• On race day: nothing new. Test your food and hydration in training; our article on nutrition before and after a Hyrox race covers these basics.

This calculator does not replace the advice of a health professional or sports dietitian, especially in case of pregnancy, medical conditions, treatment or a history of eating disorders.

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