Macro Calculator

Turn a daily calorie target into gram targets for protein, carbohydrate and fat. Pick a goal-based split — each one built to sit inside the government Acceptable Macronutrient Distribution Ranges — or set your own percentages. If you do not know your calories yet, start with the calorie calculator.

Uses the Atwater energy values (protein and carbohydrate 4 kcal/g, fat 9 kcal/g) and the IOM Acceptable Macronutrient Distribution Ranges. General information, not medical or dietetic advice.

How macros are calculated

Every calorie in your diet comes from one of three macronutrients, and each carries a fixed amount of energy per gram. Protein and carbohydrate both supply about four calories per gram, while fat is more energy-dense at nine calories per gram. Those figures, known as the Atwater factors, are the same values printed on nutrition labels, and they are all this calculator needs to turn a percentage split into grams. It multiplies your daily calorie target by the percentage assigned to each macronutrient, then divides by that macronutrient's calories-per-gram. A 2,000-calorie day at a balanced 20/50/30 split, for instance, works out to 100 grams of protein, 250 grams of carbohydrate, and about 67 grams of fat.

Because fat holds more than twice the energy of the other two, its gram total always looks small next to carbohydrate even when it makes up a healthy share of your calories. That surprises people the first time they see it, and it is the single most common reason a hand-calculated macro plan goes wrong. Letting the tool handle the arithmetic keeps the three numbers honest and consistent with your calorie goal.

Choosing a split that fits your goal

There is no single correct macro ratio, but there is a sensible range. The Institute of Medicine's Acceptable Macronutrient Distribution Ranges — the reference the U.S. government uses — put a healthy adult intake at 45 to 65 percent of calories from carbohydrate, 20 to 35 percent from fat, and 10 to 35 percent from protein. Every preset in this calculator except the deliberately lower-carb option stays inside those bounds, so you can adjust toward your goal without drifting into territory that compromises nutrient adequacy or long-term health.

If your aim is to build or hold onto muscle, nudging protein toward the top of its range is the change that matters most, because protein both drives muscle repair and keeps you full while you train. Endurance athletes tend to do the opposite, pushing carbohydrate higher to keep glycogen stores topped up for long sessions. Fat is the macronutrient most people can leave alone: keeping it somewhere between a fifth and a third of calories supports hormones and the absorption of fat-soluble vitamins without crowding out the other two. Whatever split you choose, protein is the number worth protecting first — carbohydrate and fat can flex around it based on preference and how you train.

Where this calculator stops

Macros describe the composition of your diet, not its quality. Two thousand calories of whole foods and two thousand calories of ultra-processed snacks can share an identical macro split while delivering very different amounts of fibre, micronutrients, and satiety. Use your gram targets as a frame, then fill that frame with mostly minimally processed foods — lean proteins, whole grains, legumes, fruit, vegetables, and healthy fats. This tool also assumes you already have a sound calorie target; if you do not, set that first with the calorie calculator, because the macro grams are only as accurate as the calorie number they are built on.

Frequently asked questions