How to calculate macros, step by step
To calculate macros, set your daily calories, split them between protein, carbs and fat, then turn each share into grams. Protein and carbs carry 4 calories per gram and fat carries 9, so the grams follow from the calories once the split is set. On the defaults — 2,000 calories a day at 30% protein, 40% carbs and 30% fat — the answer is 150 g protein, 200 g carbs and 67 g fat. Work it out in the macro calculator.
The worked example: 2,000 calories at 30/40/30
The worked example, line by line. Step 1 — protein's share: 30% of 2,000 calories is 600 calories. Step 2 — protein in grams: 600 calories at 4 calories per gram is 150 g. Step 3 — carbs' share: 40% of 2,000 calories is 800 calories. Step 4 — carbs in grams: 800 calories at 4 calories per gram is 200 g. Step 5 — fat's share: 30% of 2,000 calories is 600 calories. Step 6 — fat in grams: 600 calories at 9 calories per gram is 67 g. Step 7 — check the shares add up: 30% plus 40% plus 30% is 100%, and the three gram targets together carry the whole 2,000 calories. The same seven steps work for any calorie target: take the percentage, turn it into calories, divide by 4 for protein and carbs and by 9 for fat.
What a macro is
A macro is a macronutrient — protein, carbohydrate or fat — one of the three nutrients that carry the calories in food. Protein builds and repairs tissue, carbs are the body's preferred fuel for training, and fat carries the fat-soluble vitamins and supports hormones. Every food is a mix of the three in different proportions, and the macro split is the share of your daily calories each one supplies. The split is a share of calories, not a share of weight: fat carries more than twice the calories per gram, so a diet that is 30% fat by calories is far less than 30% fat by weight. That is the mistake the grams exist to prevent — the percentages describe the calories, and the grams describe the food.
Setting your calories first
The split means nothing without the calorie target, and the target comes first. Maintenance is the calories that hold your weight steady; a cut sits below it and a bulk above it, and the macro calculator takes the target you give it. Work out the target from your body and your activity — the tdee-calculator page estimates what you burn in a day, and the calorie-calculator page does the same from your stats — then bring the number here and split it. A target picked from a round number is a guess; a target from your burn is a starting point you can adjust from what the scales say over two to four weeks.
Choosing the split for your goal
The default split is 30% protein, 40% carbs and 30% fat — the balanced split, 150 g protein, 200 g carbs and 67 g fat at 2,000 calories. Losing weight pushes protein up and carbs down, because protein is the most filling macro and it protects muscle while the calories are short; gaining pushes carbs up, because carbs are the easiest calories to eat in volume and they fuel the training. The split is a starting point, not a prescription: the protein target is the one to hold steady, and the carbs and fat are the dials you turn when the calories move. Whatever split you pick, the shares must add to 100% — a split that adds to anything else is not a split, and the calculator says so plainly.
Why fat grams look small
Fat grams always look small next to protein and carbs, and that is the 9 calories per gram at work. At 30% of 2,000 calories, fat is 600 calories — the same calories as protein — but 600 calories of fat is 67 g while 600 calories of protein is 150 g. The grams are not comparable across macros: a gram of fat is worth more than twice a gram of protein or carbs, so the fat column is always the shortest and the protein and carb columns are always the longest. Judging the split by the grams instead of the calories makes fat look like an afterthought when it is a third of the diet. Read the percentages for the balance and the grams for the plate.
Common mistakes
The first is splitting the weight instead of the calories — taking 30% of the food's weight as protein, which is not the same as 30% of its calories, because fat weighs so little for its calories. The second is forgetting that the shares must add to 100% — a split that adds to 90% or 110% leaves calories unassigned or double-counted, and the grams that come out of it are wrong in both directions. The third is dividing by 4 for fat as well as for protein and carbs, which overstates the fat grams by more than double. The fourth is setting the split before the calories — the percentages describe a target, and without the target they describe nothing. The fifth is treating the grams as exact to the gram — food labels round, portions vary, and a day that lands within a few grams of each target is a day on plan. Work it out in the macro calculator, and check the tdee-calculator and the guides/how-to-convert-grams-to-calories before you decide what the answer means.
Adjusting from what happens
The calculation gives a target; the scales and the training log tell you whether it is right. Hold the targets for two to four weeks, weigh yourself under the same conditions, and watch the trend rather than any single day. If the weight is not moving the way the goal needs, move the calories first — a few hundred either way — and keep the split, because changing the calories and the split at once leaves you guessing which one did it. If the weight is moving but the training feels flat, move the carbs before the fat, because carbs are the training fuel. The macro targets are a starting point that the next month of data refines, and the calculator is there to redo the arithmetic every time the calories move.