Macro Calculator

How the macro targets are worked out

The calculator works in three steps:

1. Daily calories. Your resting energy use is estimated with the Mifflin-St Jeor equation and multiplied by an activity factor, exactly as in the calorie calculator. For a weight-loss goal it subtracts the calorie calculator’s moderate pace (500 kcal a day, about 1 lb a week, or 550 kcal for 0.5 kg in metric); for gain it adds the same amount.
2. Split. The calories are divided between protein, carbohydrate and fat by the percentages you choose. The three calorie amounts are rounded so they add up exactly to the daily total.
3. Grams. Each calorie amount is divided by the energy in a gram of that nutrient: 4 kcal for protein and carbohydrate, 9 kcal for fat.

The splits are shares of calories, not of weight. Because fat has more than twice the energy per gram, 30% of calories from fat is far fewer grams than 30% from carbohydrate.

The presets. The US Institute of Medicine set Acceptable Macronutrient Distribution Ranges (AMDRs) for adults: 10–35% of calories from protein, 45–65% from carbohydrate and 20–35% from fat. Intakes inside these ranges are associated with a lower risk of chronic disease while still supplying essential nutrients. The balanced preset (20/50/30) and the higher-protein preset (30/45/25) sit inside all three ranges. The lower-carb preset (30/35/35) puts carbohydrate below the range, and the result says so. With custom, you can enter any split that adds up to 100%.

Formulas used

BMR

10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 (men) or − 161 (women)

Energy per gram

4 kcal for protein, 4 kcal for carbohydrate, 9 kcal for fat

The 4-4-9 values are the general Atwater factors, the figures most widely used in nutrition labeling and diet planning. They are averages: the energy actually absorbed differs a little between foods, and fiber and alcohol are not counted here. Alcohol provides 7 kcal per gram and doesn’t fit into any of the three groups.

Protein is also shown per kilogram of body weight, the unit nutrition guidance uses:

Worked example

A 35-year-old man, 5 ft 10 in (177.8 cm) and 180 lb (81.65 kg), lightly active, who wants to keep his weight steady and chooses the balanced split:

1. BMR = 10 × 81.65 + 6.25 × 177.8 − 5 × 35 + 5 = 1,757.7, rounded to 1,758 kcal.
2. Daily calories = 1,758 × 1.375 = 2,417 kcal.
3. Protein: 20% of 2,417 = 483 kcal ÷ 4 = 121 g.
4. Carbohydrate: 50% of 2,417 = 1,208.5, which becomes 1,209 kcal so the three parts add up to 2,417; ÷ 4 = 302 g.
5. Fat: 30% of 2,417 = 725 kcal ÷ 9 = 81 g.
6. Over three meals: about 40 g of protein, 101 g of carbohydrate and 27 g of fat each.
7. Protein per kilogram: 121 ÷ 81.65 = 1.48 g/kg (0.67 g per lb) — above the 0.8 g/kg RDA and inside the ISSN range for people who exercise.

Choosing Lose instead lowers the target by 500 kcal to 1,917 kcal a day, giving 96 g of protein, 240 g of carbohydrate and 64 g of fat. The higher-protein split at maintenance gives 181 g of protein (2.2 g/kg), 272 g of carbohydrate and 67 g of fat.

Choosing a split

• Total calories matter most for weight. The split changes what you eat, not how many calories you need. Pick the split you can keep up with day to day.
• Protein when losing weight. In a calorie deficit a percentage split gives fewer grams of protein, so check the g/kg line. The ISSN notes that people doing resistance training while eating less may need more than 2.0 g/kg to keep muscle; the higher-protein preset raises the share.
• Quality within each group. The same grams of carbohydrate can come from vegetables, fruit, whole grains or sugar; the same fat from olive oil or processed meat. The numbers here don’t distinguish them.
• Meals don’t have to be equal. The per-meal figures are simply the daily grams divided evenly. Spreading protein across meals is a common approach for people who train, but any pattern that reaches the daily totals works for the arithmetic.

Who these numbers are not for

The estimates are for healthy adults. They don’t apply to children and teenagers, whose ranges differ; to pregnancy or breastfeeding, when protein and energy needs rise; or to anyone following a diet set by a doctor or dietitian, for example for kidney disease, diabetes or another condition where protein, carbohydrate or fat intake is managed medically. The calorie estimate is an average for people of your size and activity, and yours may be a few hundred calories higher or lower. If you have a history of disordered eating, tracking macros can do more harm than good — a doctor or registered dietitian can help set goals that suit you.