Calculator

Macro Calculator

Turn a calorie target into protein, carbohydrate, and fat grams, with food portions that actually hit them.

Supplying body fat percentage sets protein from lean mass instead of total weight, which matters most above roughly 30 percent body fat. Estimate it here if you do not know it.

Not sure? The TDEE calculator will give you a starting range. Enter the midpoint, adjusted for your goal.

Carbohydrate and fat are interchangeable for body composition once protein and total calories are fixed. Pick whichever you can actually stick to.

How this works

Most macro calculators start with a percentage split (40/30/30, 50/25/25) and back into grams. That is the wrong order of operations. Percentage splits give a 120 lb woman and a 240 lb man the same relative protein intake, when their actual requirements scale with lean tissue, not with calories.

This calculator sets the macros in the order they actually matter:

1. Protein, from body composition

Protein comes first because it is the only macronutrient with a hard requirement tied to lean mass. Targets run from 1.6 g/kg for general maintenance up to 2.4 g/kg during an aggressive deficit, in line with the International Society of Sports Nutrition position stand and Morton's meta-analysis. Requirements go up, not down, when calories go down: during a deficit the body is looking for amino acids and will take them from muscle if the diet does not supply them.

If you enter a body fat percentage, protein is calculated from lean body mass instead of scale weight. Above roughly 30 percent body fat this produces a meaningfully lower and more appropriate target, because adipose tissue does not have the same protein turnover as muscle.

2. Fat, with a floor

Dietary fat is capped on the low end, not the high end. Below about 0.5 g/kg of body weight you start running into problems with fat-soluble vitamin absorption (A, D, E, K), essential fatty acid intake, and in some people, reproductive hormone production. Very low fat diets in resistance-trained men have been associated with reduced testosterone, though the effect size is modest and the literature is not unanimous. This calculator will not take you below 0.5 g/kg regardless of which preference you select.

Above that floor, fat intake is a preference variable. Higher fat improves satiety per calorie for some people and worsens it for others.

3. Carbohydrate, filling the remainder

Carbohydrate takes whatever calories are left. This is not a demotion. Carbohydrate is the macronutrient most directly tied to training quality: glycogen availability determines how many hard sets you can produce, and depleted glycogen degrades performance long before it affects anything else. If your training feels flat during a cut, carbohydrate is the first thing to check.

On a ketogenic preference, the order flips: carbohydrate is fixed at 25 to 35 g/day to maintain nutritional ketosis, and fat absorbs the remainder.

Energy density constants

Protein: 4 kcal/g  |  Carbohydrate: 4 kcal/g  |  Fat: 9 kcal/g  |  Alcohol: 7 kcal/g

These are Atwater factors, which are averages. Real metabolizable energy varies: fiber contributes closer to 2 kcal/g, protein has a thermic effect of 20 to 30 percent compared with 5 to 10 percent for carbohydrate and 0 to 3 percent for fat, and whole foods with intact cell walls yield less energy than their label claims. The practical effect is that a high-protein, high-fiber diet delivers slightly fewer usable calories than the arithmetic suggests.

Hit protein and calories, then stop worrying. If you land within 10 g of your protein target and within 100 kcal of your calorie target, the carbohydrate and fat split is a rounding detail. Precision on the other two buys almost nothing.

Fiber is not optional

The calculator includes a fiber target of 14 g per 1,000 kcal, the Institute of Medicine's adequate intake benchmark. Roughly 5 percent of American adults meet it. Fiber counts inside your carbohydrate total, so a low-carb preference makes the fiber target harder rather than impossible: non-starchy vegetables, avocado, chia, flax, and nuts carry fiber at a low net-carb cost.

Chronic kidney disease changes these numbers. High-protein intakes are safe in people with healthy kidneys, and the meta-analytic evidence on that is now strong. They are not appropriate in established renal impairment, where protein is usually restricted. If you have reduced kidney function, use targets set by your nephrologist rather than this tool.

Related calculators

TDEE Calculator sets the calorie target this page splits.
Protein Intake Calculator goes deeper on protein distribution and timing.
Body Composition Tracker uses real scan data to sharpen these targets over time.
Fiber Diversity Score checks whether your fiber comes from enough different sources.

References

Jager 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.

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(6):376-384.

Hu S, Hsu C, Feng D, et al. Effects of low-fat diets on testosterone in men: systematic review and meta-analysis of intervention studies. J Steroid Biochem Mol Biol. 2021;210:105878.

Devries MC, Sithamparapillai A, Brimble KS, et al. Changes in kidney function do not differ between healthy adults consuming higher- versus normal- or lower-protein diets: a systematic review and meta-analysis. J Nutr. 2018;148(11):1760-1775.

Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press; 2005.