Calorie and macro calculator

How the numbers are worked out

Step one is your resting energy expenditure: the calories you burn just staying alive. This calculator uses the Mifflin-St Jeor equation, with weight in kilograms, height in centimeters and age in years.

Men:    10 x weight + 6.25 x height - 5 x age + 5
Women:  10 x weight + 6.25 x height - 5 x age - 161

Step two multiplies that by an activity factor (1.2 to 1.725) to estimate what you burn in a normal day. Step three adds or removes calories for your goal. Fat is set at 25% of calories, protein at 1.6 or 2.0 grams per kilogram, and carbs are what is left.

Where it comes from, and its limits

• The equation comes from Mifflin and colleagues (1990), who measured resting energy expenditure in 498 healthy adults aged 19 to 78 and fitted the formula to their data. It is less reliable outside that age range, and for anyone who is pregnant, breastfeeding or managing a medical condition.
• The activity factors are a convention, not measurements. They are the same four the Vital app uses.
• The goal adjustment works from a weekly change of 0.25%, 0.5% or 0.75% of body weight and the usual rule of thumb that a pound of body weight is about 3,500 calories. That rule is rough, and real weight change varies.
• The result is an estimate. If you have a medical condition, are under 18, or the target comes out below your resting burn, ask a doctor or dietitian before changing how you eat.

Sources

1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51(2):241-247. doi:10.1093/ajcn/51.2.241
2. More on how the Vital app uses this: How Vital works out your daily targets. For the protein number: protein calculator.