Macro Calculator
You have a calorie number. This turns it into grams of protein, carbs and fat — and then into what that means per meal.
Split
Total: 100%
Protein
grams a day
— kcal ·— g per meal
Carbs
grams a day
— kcal ·— g per meal
Fat
grams a day
— kcal ·— g per meal
This is a calculator, not medical advice. It works only on the numbers you type in. What suits you personally depends on things this page knows nothing about — your health, your medication, your history — and a doctor or registered dietitian is the right source for that. Total calories drive weight change; the split mostly changes how the eating feels.
Grams on a page, grams on a plate
The hard part is knowing what you actually ate. Food Cal AI reads a meal from a photo or a typed description, gives you its calories and macros, and keeps the running total against your day.
The whole calculation
Macros are shares of your calories, so the sum is short: multiply the calorie target by each percentage, then divide by the energy in a gram of that macro. Protein and carbohydrate carry about 4 kilocalories per gram, fat about 9. A 2,000 calorie day at 30% protein is 600 calories from protein, which is 150 grams.
That factor of 9 is why fat percentages feel small. Thirty per cent of calories from fat is about 67 grams, while the same share of carbohydrate is 150 — the numbers look lopsided because fat is more than twice as energy-dense, not because the split is unbalanced.
| Split | Protein | Carbs | Fat | Usually chosen for |
|---|---|---|---|---|
| Balanced | 30% | 40% | 30% | A default when nothing else applies |
| High protein | 40% | 30% | 30% | Keeping protein up while calories are down |
| Low carb | 35% | 20% | 45% | Preference, or steadier appetite through the day |
| Keto | 25% | 5% | 70% | Carbohydrate low enough to shift fuel use |
Percentages or grams per kilogram?
Both are used, and they answer slightly different questions. A percentage split describes the shape of a diet and stays constant as calories move. Grams per kilogram of body weight describes an absolute requirement — protein in particular is usually written that way, because the amount a body can use is tied to its size rather than to how much you happen to be eating.
The difference shows up in a deficit. Hold protein at 30% of calories and cut calories by 500, and the grams of protein fall with them. Set protein per kilogram instead and it stays put while the other two absorb the cut. That is why the calorie calculator on this site sets protein per kilogram, and this page does not — it is working from a number you already decided.
What the split does and does not change
The evidence is reasonably consistent that total energy intake is what drives weight change, and that macro ratios matter much less for that than the internet suggests. Where the split does earn its keep is everything around adherence: how full you feel, how much energy you have in training, whether the food fits how you actually like to eat.
Which makes the practical test a simple one. A split you can follow for months beats a theoretically better one you abandon in a fortnight, and if two options look equally sensible on paper, the tiebreaker is which one describes food you would eat anyway.
Questions
How is this different from the calorie calculator?
They start from opposite ends. The calorie calculator works out a calorie target from your height, weight, age and activity, then sets protein from your body weight. This page assumes you already have a calorie number and splits it by percentage, which is how ratio-based plans — 40/30/30, keto — are actually written down. Use that one to get the number, this one to divide it up.
Why do the percentages have to add up to 100?
Because they are shares of the same calorie total. If they add to 90, the grams shown only account for 90% of what you planned to eat, and the missing tenth has to come from somewhere. The calculator tells you the total rather than silently correcting it, because quietly rescaling your numbers would hide the mistake rather than fix it.
Where do 4, 4 and 9 come from?
They are the Atwater factors: the average usable energy in a gram of protein, carbohydrate and fat — roughly 4, 4 and 9 kilocalories. They are averages across food types rather than exact constants, which is one reason any macro target is a working figure and not a measurement. Alcohol, for what it is worth, is about 7.
Does the per-meal split have to be even?
No, and for most people it will not be. Dividing by the number of meals is a starting point that makes the daily numbers easier to picture — in practice protein tends to spread more evenly than carbs, and people eating three meals plus training rarely want all three identical. Treat the per-meal figure as a rough target rather than a rule.
Which split is the right one?
That is a question about you, and this page cannot answer it. What it can say is that total calories drive weight change and the split mostly affects how the eating feels — how full you are, how training goes, how easy the plan is to keep to. Anyone with a medical condition, or working towards a specific athletic goal, is better served by a registered dietitian than by a percentage picked off a website.
