Macro Calculator

Calculator

How the split is calculated

Four steps, in this order, and the order is what makes the output defensible. Step one is the calorie budget. If you leave the calorie field blank, that budget is your estimated maintenance: a Mifflin–St Jeor basal metabolic rate multiplied by an activity factor between 1.2 and 1.9. If you enter a daily calorie target instead, that number is used and maintenance is shown alongside it for reference, so you can see how far below or above it you are working.

Step two is protein, set as grams per kilogram of bodyweight: 1.6, 1.8 or 2.2 g/kg depending on the emphasis you choose. Step three is fat, set at the higher of 0.8 g per kilogram of bodyweight or 20% of the calorie budget; taking the higher of the two means the floor holds both for a large person on few calories and for a small person on many. Step four is carbohydrate, which is simply the calories left over, divided by four.

Converting between grams and calories uses the Atwater general factors: protein and carbohydrate supply about 4 kcal per gram, fat about 9. The result panel prints that multiplication back out so you can check it: the grams times their energy values should land within a few kilocalories of your budget, and the small difference is nothing but the rounding of grams to whole numbers. If protein and the fat floor together exceed the budget, which happens at very low calorie targets for larger people, the two are scaled down proportionally and the panel says so rather than printing a negative carbohydrate figure.

The logic behind the split

Protein anchors the plan: meta-analyses put the ceiling of useful intake for muscle retention and growth around 1.6 g/kg for most, with 2.2 g/kg justified while cutting or training hard. Fat below roughly 0.8 g/kg (or ~20% of calories) risks hormonal disruption, so we floor it. Everything left is carbohydrate, not because carbs don't matter, but because within a fixed calorie and protein budget, the carb-versus-fat ratio is mostly personal preference and training-fuel pragmatism. If the budget can't fit your protein and fat targets, we scale them down proportionally and say so rather than printing a negative carb figure.

The sequence matters more than the ratios do. A split that starts from percentages (the familiar 40/30/30 and its cousins) produces a protein target that changes when your calories change, which is exactly backwards: your protein requirement tracks your bodyweight and your training, not how much you happen to be eating this month. Anchoring protein and fat in grams per kilogram and letting carbohydrate absorb the variation keeps the two constrained numbers constant and puts the flexibility where it belongs.

Protein: how much, and why

The 1.6 g/kg figure is the headline of Morton and colleagues' 2018 meta-analysis in the British Journal of Sports Medicine, which pooled forty-nine studies and 1,863 participants and found that resistance-training gains in lean mass improved as protein intake rose up to about 1.6 g per kilogram per day and then stopped improving. The confidence interval around that breakpoint extended to 2.2 g/kg, which is where the upper option on this page comes from. Above that range, more protein reliably produces more expensive urine and not much else.

Three situations justify sitting at the top of the range rather than the bottom. A calorie deficit is the first and the most important: energy is short, the body will break down tissue to cover the gap, and higher protein plus resistance training is what steers that toward fat rather than muscle. Heavy or frequent training is the second. Being older is the third: anabolic resistance means the same dose of protein produces a smaller response after about sixty, so the requirement per kilogram rises rather than falls with age, which is the opposite of what most people assume.

Two practical caveats. If you are carrying a lot of body fat, grams per kilogram of total bodyweight overshoots, because fat mass has no meaningful protein requirement. Setting the target from lean mass or from a goal weight is more sensible, and our lean body mass calculator will give you that figure. And high protein intakes are not a problem for healthy kidneys; that concern comes from people who already have kidney disease, for whom protein intake is genuinely a clinical matter and should be set by a renal dietitian rather than a web page.

Fat: why there is a floor

Fat is the only macronutrient on this page with a hard minimum, and it is there because the consequences of getting it wrong are not about performance but about function. Dietary fat carries vitamins A, D, E and K into the body, supplies the essential fatty acids the body cannot make, and provides the substrate for steroid hormone production. Sustained very low fat intakes are associated with falling testosterone in men and with menstrual disruption in women, and the review literature on physique athletes (the group most likely to push fat down in pursuit of a leaner look) treats a floor as non-negotiable for that reason.

The floor used here is the higher of 0.8 g per kilogram of bodyweight or 20% of the calorie budget. Taking the higher of the two is deliberate: a percentage alone fails a large person eating very little, and a gram-per-kilogram figure alone fails a small person eating a great deal. Whichever produces more fat wins, so both failure modes are covered.

None of this makes more fat better. Above the floor, fat is simply a currency you can trade against carbohydrate, and the trade is a preference question. What the floor does is stop the trade running off the end of the table, which is what happens when a calorie budget gets squeezed and fat is treated as the flexible one because it is the most energy-dense.

Carbohydrate: the remainder, and what it is for

Carbohydrate gets what is left, and that placement is not a demotion. It reflects an honest reading of the evidence: once calories and protein are matched, trials comparing higher-carbohydrate and lower-carbohydrate diets find very small differences in fat loss between them. The variable that does the work is adherence, and adherence is personal. Somebody who feels better on porridge and rice should not be handed a ketogenic split because a calculator decided carbohydrate was optional.

Carbohydrate is, however, the macronutrient that most clearly changes what training feels like. Glycogen is the dominant fuel for anything hard and repeated (intervals, a heavy session, a long ride), and a lower-carbohydrate day shows up in the last third of a session before it shows up anywhere else. That is why the practical advice is to put carbohydrate where the training is: more on hard days, less on rest days, if you want to manage it that finely. Most people do not need to, and holding the same target every day is a perfectly good plan.

Fibre lives inside the carbohydrate figure rather than beside it. The Institute of Medicine's Adequate Intake is 14 grams of total fibre per 1,000 kilocalories (28 g on a 2,000 kcal day), and the result panel works that out for your budget. It is the single number most people miss by the widest margin, and it does a disproportionate amount of the work of making a calorie target liveable, because high-fibre foods are bulky, slow to eat and satisfying at a given calorie count.

Adjusting for a cut, maintenance or a gain

The calorie budget changes; the rules do not. In a cut, take the target from our calorie deficit calculator and enter it in the calorie field here, or follow the link that calculator provides, which fills it in for you. Set the protein emphasis to cutting, at 2.2 g/kg, because a deficit is the condition where protein is doing the most work. Expect carbohydrate to take most of the squeeze, since protein and the fat floor are protected. If carbohydrate comes out implausibly low, the deficit is too deep for your size rather than the split being wrong.

At maintenance, leave the calorie field blank and the page uses your estimated TDEE. This is the setting most people should spend most of the year at, and it is also the one worth measuring against: if the maintenance estimate is right, your weight holds within a kilogram over a month. If it does not, the estimate, not the split, is what needs adjusting, and the error band on any TDEE prediction is about ten to fifteen per cent.

In a gaining phase, take the target from the calorie surplus calculator and enter it the same way. Protein stays in the same 1.6–2.2 g/kg band; the requirement does not rise just because you are eating more. What changes is that there is now plenty of room for carbohydrate, which is what fuels the training that makes a surplus worth running in the first place. Re-run the numbers every four to six weeks in any phase, because the protein target is per kilogram and your kilograms are moving.

Timing and distribution across the day

Total daily intake is the first-order variable and distribution is the second-order one, but the second order is not nothing. The International Society of Sports Nutrition's position stand on protein and exercise puts the dose that maximally stimulates muscle protein synthesis at roughly 0.25 g per kilogram of bodyweight per serving, or about 20–40 grams, repeated every three to four hours across the waking day. For most people that lands on four meals, which is why the result panel shows the split at three, four and five.

Three meals works if the meals are large enough to clear the per-serving dose, which for an 80 kg adult means about 20–30 g of protein minimum. Five suits people who train twice a day, who struggle with large meals, or who simply prefer eating more often. Older adults may need the larger end of the per-serving range (closer to 40 g) to get the same response, which is another reason the total matters more than the schedule for anyone over sixty.

Carbohydrate and fat timing is a much smaller lever than the internet suggests. The one genuinely useful rule is to put a meaningful share of the day's carbohydrate in the hours either side of hard training, because that is where glycogen availability changes how the session goes and how well you recover from it. Beyond that, eating fat in the evening does not store it differently, carbohydrate after dark is not a separate food group, and the anabolic window is hours wide rather than minutes. Build the schedule you will actually keep.

Where macro targets are actually used

Outside fitness apps, macronutrient targets are routine clinical and sporting arithmetic. Sports dietitians working with endurance and team-sport athletes plan carbohydrate in grams per kilogram of bodyweight per day and periodise it against the training week; the protein and fat targets are then set around it. Physique and weight-category athletes work the other way, anchoring protein high and letting the other two move, which is the same logic this page applies.

In clinical dietetics, macronutrient distribution is prescribed rather than suggested: protein targets in renal disease, in critical care, and in the management of sarcopenia in older adults; carbohydrate distribution across meals in type 1 and type 2 diabetes, where it interacts directly with insulin dosing; fat distribution in lipid disorders and in fat malabsorption. Anyone on insulin or a sulfonylurea should treat a change in carbohydrate intake as a medication question first and a diet question second.

Public-health nutrition uses the same units at population scale. The Institute of Medicine's Acceptable Macronutrient Distribution Ranges (10–35% of calories from protein, 45–65% from carbohydrate, 20–35% from fat) are the reference bands most national guidelines are built on, and the fat floor used on this page sits at the bottom edge of that fat range rather than below it. The split produced here is a personalised version of an ordinary, mainstream set of targets, not an alternative to them.

How it's calculated

Worked example: an 80 kg man on a 2,200 kcal cutting target

1. Calorie budget: 2,200 kcal, entered by hand or carried over from the calorie deficit calculator. Maintenance for this person is shown alongside it (say 2,760 kcal), so the target is 560 kcal below it.
2. Protein at the cutting emphasis: 80 × 2.2 = 176 g, which is 176 × 4 = 704 kcal.
3. Fat floor, first candidate: 80 × 0.8 = 64 g. Second candidate: 20% of 2,200 = 440 kcal ÷ 9 = 48.9 g. The higher wins, so fat is 64 g, which is 64 × 9 = 576 kcal.
4. Carbohydrate takes the remainder: 2,200 − 704 − 576 = 920 kcal, and 920 ÷ 4 = 230 g.
5. The split is 176 g protein, 230 g carbohydrate, 64 g fat (or 32% protein, 42% carbohydrate, 26% fat).
6. Check-sum: (176 × 4) + (230 × 4) + (64 × 9) = 704 + 920 + 576 = 2,200 kcal. Exactly on budget.
7. Protein per meal: 176 ÷ 4 = 44 g at four meals, 176 ÷ 3 = 59 g at three, 176 ÷ 5 = 35 g at five. All three clear the roughly 0.25 g/kg (20 g for this man) per-serving threshold.
8. Fibre: 2,200 ÷ 1,000 × 14 = 31 g a day, drawn from the 230 g of carbohydrate rather than added to it.
9. An alternative split at 30% of calories from fat: 2,200 × 0.30 ÷ 9 = 73 g fat, leaving 2,200 − 704 − 660 = 836 kcal, or 209 g of carbohydrate. Same calories, same protein, 9 g more fat and 21 g less carbohydrate: a preference, not an improvement.

Where this number is used in the real world

• Everyday diet planning, where a target in grams is something you can shop for and weigh, while a percentage is not.
• Sports nutrition, where carbohydrate is periodised against the training week and protein is held at a fixed grams-per-kilogram figure.
• Physique and weight-category sport, where protein is anchored high through a cut and carbohydrate and fat absorb the shrinking budget.
• Clinical dietetics, where protein targets in renal disease, critical care and sarcopenia, and carbohydrate distribution in diabetes, are prescribed in grams.
• Food-tracking apps and coaching practice, as the underlying arithmetic behind the numbers a tracker displays.
• Public-health nutrition, where the Acceptable Macronutrient Distribution Ranges give the population-level bands these personal targets sit inside.
• Sanity-checking a plan someone has sold you: the check-sum on this page shows in one line whether the grams you were given add back to the calories you were promised.

Frequently asked questions

Keep going

A single number rarely tells the whole story. Alongside the macros result, the calorie deficit calculator, the TDEE calculator, the protein calculator, the calorie surplus calculator and the lean body mass calculator each add a different angle on the same measurements. For the reasoning behind the numbers, read TDEE explained and Track without DEXA.

Sources

1. Morton RW, Murphy KT, McKellar SR, et al. 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. Br J Sports Med 2018;52:376–84. doi.org/10.1136/bjsports-2017-097608
2. Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr 2017;14:20. doi.org/10.1186/s12970-017-0177-8
3. Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr 2014;11:20. doi.org/10.1186/1550-2783-11-20
4. Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington DC: National Academies Press, 2005. Total fibre Adequate Intake of 14 g per 1,000 kcal. doi.org/10.17226/10490
5. Institute of Medicine. Dietary Reference Intakes summary tables (fibre Adequate Intake 38 g/d men, 25 g/d women). National Academies Press. www.ncbi.nlm.nih.gov/books/NBK56068/table/summarytables.t4/
6. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51:241–7. doi.org/10.1093/ajcn/51.2.241