Calorie and macro calculator
From your sex, age, weight, height and activity, it estimates the calories you use a day and splits them into protein, fat and carbs for your goal. It uses the Mifflin-St Jeor equation. It is a starting point: the data that counts is how your weight moves over the next few weeks.
With your goal
2,155 kcal/day
- Resting metabolism
- 1,389 kcal/day
- To maintain your weight
- 2,153 kcal/day
- Protein
- 117 g
- Fat
- 67 g
- Carbs
- 271 g
Meant for healthy adults. Not for pregnancy or breastfeeding, and if you have or have had a difficult relationship with food, speak to a professional first.
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How it is worked out
- Resting metabolism, with Mifflin-St Jeor: 10 × weight in kg + 6.25 × height in cm − 5 × age, plus 5 for men or minus 161 for women.
- Maintenance: that number times an activity factor, from 1.2 to 1.9.
- Goal: a percentage is added or taken off.
- Macros: protein per kilo of body weight, fat as a share of calories, and carbs for the rest.
For example, a 30-year-old woman, 65 kg and 168 cm: 10 × 65 + 6.25 × 168 − 5 × 30 − 161 = 1,389 kcal at rest. With moderate activity (× 1.55), about 2,153 kcal to maintain her weight. At 1.8 g/kg of protein that is 117 g, and at 28% fat, about 67 g.
How far to trust the result
A systematic review compared the most used equations and found Mifflin-St Jeor the most reliable: it came within 10% of measured metabolism in more people than the others (Frankenfield et al., 2005). It also notes that older adults and ethnic minorities living in the US are under-represented in those studies. And the activity factor is another estimate on top. Treat the number as your first test: keep to it for two or three weeks, watch the trend in your weight and adjust.
Why 1.8 g/kg of protein by default
A meta-analysis of 49 studies in people doing resistance training found that, beyond a total intake of 1.62 g/kg a day, protein supplements added no further fat-free mass (Morton et al., 2018). That is an average, with uncertainty, from studies in healthy people, so 1.8 g/kg leaves a small margin. It is a starting value you can change.
Frequently asked questions
- What is resting metabolism?
- The energy your body uses to run while at rest, not counting activity or digestion.
- Which activity level should I pick?
- If in doubt, the lower of the two: overestimating is easy. Then correct it with what your weight does.
- How big a deficit is reasonable?
- It depends on the person. Cuts of 10 to 20% are the usual ones; beyond 25% they are hard to sustain, and the calculator warns you.
Sources
- Mifflin et al., 1990. A new predictive equation for resting energy expenditure in healthy individuals. The American Journal of Clinical Nutrition, 1990. 10.1093/ajcn/51.2.241
- Frankenfield et al., 2005. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association, 2005. 10.1016/j.jada.2005.02.005
- Morton et al., 2018. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 2018. 10.1136/bjsports-2017-097608