Most macro calculators online use the same lazy template: estimate calories, slap on a 40 percent carb / 30 percent protein / 30 percent fat split, and call it personalized. The split is not personalized to anything. It treats a 55 kg sedentary office worker and a 95 kg powerlifter as if they need the same protein-to-calorie ratio, which they obviously do not.
This calculator builds your numbers in the order the peer-reviewed literature actually supports. Calories first, anchored to your real body. Protein second, in absolute grams per kilogram of body weight from the 2018 Morton meta-analysis. Fat third, at a hormonal-health floor. Carbs last, as whatever calories are left to hit your goal. Every multiplier maps to a specific paper. The result is a target that scales with body size, training experience, and what you are actually trying to do.
How this calculator works
There are four steps under the hood, each grounded in a primary source.
- BMR (Mifflin-St Jeor): For men, BMR equals 10 times weight in kg plus 6.25 times height in cm minus 5 times age in years plus 5. For women, the constant at the end is minus 161 instead of plus 5. The Mifflin-St Jeor equation, published by Mifflin et al. 1990 in the American Journal of Clinical Nutrition, was validated against indirect calorimetry and predicts resting energy expenditure within roughly 10 percent for most healthy adults.
- TDEE (activity multiplier): Multiply BMR by an activity factor of 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (very active), or 1.9 (extra active). These multipliers come from the standard Harris-Benedict / Mifflin literature and the FAO/WHO physical activity level coefficients used in dietary guidelines. They are estimates, not measurements. Most adults find their real maintenance is within 200 kcal of the calculator's output after two weeks of weighed food and bodyweight tracking.
- Goal calorie target: For a cut, multiply TDEE by 0.80 (a 20 percent deficit). Advanced trainees willing to accept faster lean-mass risk can go to 0.75. For maintenance, use TDEE as is. For a bulk, multiply by 1.10 to 1.15. The 25 percent deficit cap is the upper bound recommended in the Helms et al. 2014 review on protein during caloric restriction in the International Journal of Sport Nutrition and Exercise Metabolism. Cuts deeper than that lose more muscle than fat in the long run.
- Protein: Sedentary adults get 1.2 g/kg per the Phillips, Chevalier, and Leidy 2016 review. Beginner trainees get 1.6 g/kg, the lower bound of the Morton et al. 2018 meta-analysis in the British Journal of Sports Medicine. Intermediate trainees get 1.8 g/kg. Advanced trainees in a deficit get 2.2 g/kg per the Helms et al. 2014 contest-prep paper, which scales protein up during cuts to preserve lean mass. Adults 65 and older get a 1.6 g/kg floor regardless of training status, per the PROT-AGE consensus (Bauer et al. 2013). The cap is 2.4 g/kg, since Antonio et al. 2015 pushed resistance-trained adults to 3.4 g/kg with no harm but no added body-composition benefit.
- Fat: Defaults to 0.8 g/kg, a sensible hormonal-health target from Helms et al. 2014. The practical floor is 0.6 g/kg per the 2017 ISSN position stand on diets and body composition (Aragon et al.). Below about 20 percent of total calories from fat, sex hormones (testosterone in men, menstrual function in women) take a measurable hit.
- Carbs: Whatever calories remain after protein and fat, divided by 4 (since carbs supply 4 kcal per gram, the same as protein, while fat supplies 9). This is the most flexible macro because it is not bound by a hormonal-health minimum or a muscle-protein-synthesis ceiling.
If you only care about the protein number, our protein calculator gives you a focused, goal-aware target without computing fat and carbs. The two tools use compatible logic, so you will see the same protein number cross-referenced between them.
Cut, maintain, or bulk: pick the right deficit or surplus
If you are cutting
The default cut is a 20 percent deficit below maintenance for most lifters, and a 25 percent deficit for advanced trainees who can tolerate a steeper drop. For a 75 kg intermediate lifter on 2,633 kcal maintenance, the 20 percent cut lands at roughly 2,106 kcal, which works out to about 0.5 kg of fat loss per week if your activity stays steady. Protein moves up to protect muscle: intermediate lifters jump to 2.0 g/kg, advanced lifters to 2.2 g/kg. The Helms 2014 review found that lean athletes in a deficit need protein levels well above maintenance recommendations to hold lean mass, with some bodybuilders during contest prep needing 2.3 to 3.1 g/kg of fat-free mass.
The 25 percent deficit cap exists for a reason. The Helms paper traced the dose-response: as the deficit deepens, the percentage of weight lost from lean tissue rises. Below about 75 percent of TDEE, you are losing one or two grams of lean mass for every three or four grams of fat. That is a bad trade if the goal is to look better, not just to weigh less. We surface a warning in the result card when you push past the 25 percent line.
If you are maintaining
Maintenance is the most useful state to spend time in if you do not have an active body-composition goal. It is also where the calculator is most accurate, because there are no goal-driven adjustments to compound calorie estimation error. If your bodyweight has held steady for the last month, the calorie number you log over those four weeks is your real maintenance, regardless of what the calculator predicts. Use that.
If you are bulking
The default bulk is a 12.5 percent surplus, which targets roughly 0.25 to 0.5 percent of bodyweight per week of weight gain. For a 75 kg lifter, that is 200 to 400 grams per week. Smaller surpluses bias toward a higher proportion of the gain being lean mass. Larger surpluses gain weight faster, but the marginal extra weight is mostly fat. The 2014 review by Helms et al. on natural bodybuilding contest preparation summarizes the evidence: aggressive bulks deliver roughly the same lean-mass gain as conservative bulks, but with much more fat to cut later.
Worked examples (for quick reference)
Here are six common scenarios with the calculator output. Each row uses different inputs to show how training experience and goal change the macro split.
| Person | Goal | Calories | Protein | Fat | Carbs |
|---|---|---|---|---|---|
| 30y M, 5 ft 10 in, 170 lb178 cm, 77 kg, moderate activity, intermediate | Maintain | 2,693 kcal | 139 g (1.8 g/kg) | 62 g (0.8 g/kg) | 396 g |
| 30y M, 5 ft 9 in, 165 lb175 cm, 75 kg, moderate activity, advanced | Cut (-25%) | 1,975 kcal | 165 g (2.2 g/kg) | 60 g (0.8 g/kg) | 194 g |
| 22y M, 5 ft 11 in, 154 lb180 cm, 70 kg, moderate activity, beginner | Bulk (+12.5%) | 2,999 kcal | 112 g (1.6 g/kg) | 56 g (0.8 g/kg) | 512 g |
| 35y F, 5 ft 5 in, 143 lb165 cm, 65 kg, sedentary, sedentary | Maintain | 1,614 kcal | 78 g (1.2 g/kg) | 52 g (0.8 g/kg) | 208 g |
| 28y F, 5 ft 7 in, 150 lb170 cm, 68 kg, very active, advanced | Cut (-25%) | 1,865 kcal | 150 g (2.2 g/kg) | 54 g (0.8 g/kg) | 194 g |
| 70y M, 5 ft 8 in, 172 lb172 cm, 78 kg, light activity, sedentary | Maintain | 2,076 kcal | 125 g (1.6 g/kg) | 62 g (0.8 g/kg) | 254 g |
Knowing your macros is the easy part. Building the workouts that move them is harder.
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Take the Free Assessment Free • 2 minutes • No credit cardPer-meal distribution: the leucine threshold still matters
Total daily macros are the dominant variable. Distribution matters at the margins, mostly for protein. Schoenfeld and Aragon 2018 in the Journal of the International Society of Sports Nutrition recommend roughly 0.4 g of protein per kg of body weight at each of four meals, totaling about 1.6 g/kg/day at the floor. Each meal of that size contains roughly 2.5 g of leucine, which is the threshold dose for a full muscle-protein-synthesis response in adults under 65. We unpack the meal-level science in our companion piece on the leucine threshold.
Carbs and fat distribute more flexibly. Some people prefer the bulk of their carbs around training, which is reasonable but not required. Others tolerate larger fat-heavy meals at the start or end of the day. Total daily intake is what moves body composition. Distribution is what makes the day comfortable to eat. We covered the broader timing question in why the anabolic window is a myth.
Three myths the calculator deliberately ignores
Myth 1: low-carb is always better for fat loss
It is not. The 2017 ISSN diet review (Aragon et al.) summarized the head-to-head trials: when protein and calories are matched, low-carb and high-carb diets produce similar fat loss over weeks to months. Low-carb has an early water-weight advantage that fades. The factors that actually matter for cutting are total calorie deficit, protein intake high enough to preserve muscle, and adherence over the multi-month timescale that body composition responds on. We covered this in more depth in our piece on body recomposition.
Myth 2: you have to eat exactly 1 gram of protein per pound
This rule of thumb (about 2.2 g/kg) sits at the high end of the evidence-based range, not the middle. The Morton 2018 meta-analysis put the plateau at 1.62 g/kg, with the 95 percent confidence interval running from 1.03 to 2.20 g/kg. Eating 1 g/lb is not harmful (Antonio 2015 went to 3.4 g/kg with no adverse effects), but it is also not necessary for most lifters. The calculator scales protein by training experience inside the established window so beginners are not over-targeting and advanced lifters in a deficit are not under-targeting.
Myth 3: carbs at night make you fat
They do not, calorie-for-calorie. Studies that controlled total daily calories found no difference in fat gain or fat loss based on when carbohydrates were eaten. The mechanism people cite (insulin storage at night) does not survive contact with the data. What matters is whether eating most of your carbs at night helps or hurts your total daily intake. For some people it helps with sleep and adherence. For others it pushes them over their calorie target. Choose the distribution that makes your full-day macros sustainable.
When to ignore this calculator
The calculator is built for healthy adults using common goal categories. A few situations require professional input rather than a generic tool.
- Pregnancy and lactation. Calorie and protein needs rise during the second and third trimesters and during lactation. Defer to your obstetric care team for individualized targets.
- Chronic kidney disease. Protein recommendations for CKD are different and depend on stage. Talk to a nephrologist or registered dietitian.
- Eating disorders or recent recovery. A registered dietitian who specializes in eating disorders is a better fit than any generic calculator.
- Diabetes. Carbohydrate intake interacts directly with insulin dosing and glycemic control. Set carb targets with a clinician or certified diabetes educator, not a calculator.
- Elite or competitive athletes. Contest prep, weight-class sports, and high-volume endurance training all have specific peri-workout fueling and carb-periodization needs that go past what a general macro calculator covers. A sports dietitian is the right partner.
For everyone else, the numbers above are a defensible starting point. Hit your target consistently for two to three weeks, weigh yourself in a stable rhythm (same time, same conditions), and adjust based on the trend, not single days.
Related reading
References
- 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(2):241-247. doi:10.1093/ajcn/51.2.241
- 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. doi:10.1136/bjsports-2017-097608
- Aragon AA, Schoenfeld BJ, Wildman R, et al. "International society of sports nutrition position stand: diets and body composition." J Int Soc Sports Nutr. 2017;14:16. doi:10.1186/s12970-017-0174-y
- 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:10.1186/1550-2783-11-20
- Phillips SM, Chevalier S, Leidy HJ. "Protein requirements beyond the RDA: implications for optimizing health." Appl Physiol Nutr Metab. 2016;41(5):565-572. doi:10.1139/apnm-2015-0550
- Bauer J, Biolo G, Cederholm T, et al. "Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group." J Am Med Dir Assoc. 2013;14(8):542-559. doi:10.1016/j.jamda.2013.05.021
- Antonio J, Ellerbroek A, Silver T, et al. "A high protein diet (3.4 g/kg/d) combined with a heavy resistance training program improves body composition in healthy trained men and women." J Int Soc Sports Nutr. 2015;12:39. doi:10.1186/s12970-015-0100-0
- Schoenfeld BJ, Aragon AA. "How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution." J Int Soc Sports Nutr. 2018;15:10. doi:10.1186/s12970-018-0215-1
- Helms ER, Zinn C, Rowlands DS, Brown SR. "A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes." Int J Sport Nutr Exerc Metab. 2014;24(2):127-138. doi:10.1123/ijsnem.2013-0054
Frequently Asked Questions
What macros should I eat to lose weight?
For most adults cutting fat, set calories at roughly 80 percent of maintenance, set protein at 1.8 to 2.2 g/kg of body weight per day to preserve lean mass, set fat at 0.6 to 0.8 g/kg for hormonal health, and let carbs fill the remainder. The Helms et al. 2014 review in the International Journal of Sport Nutrition and Exercise Metabolism showed that protein needs go up during a deficit, not down. Advanced trainees in aggressive cuts often need 2.4 to 3.1 g/kg of fat-free mass to fully protect muscle, per the Helms 2014 contest-prep paper.
Is the 40/30/30 macro split good?
Probably not for you specifically. The 40/30/30 ratio (carbs/protein/fat) is a one-size-fits-all heuristic from the Zone Diet era that ignores body weight. The evidence-based approach is to set protein in absolute grams per kilogram of body weight, set fat at a hormonal-health floor, and let carbs fill the remainder. The actual percentages that fall out vary widely. A 70 kg adult cutting on 1900 calories might land at 30 percent protein and 45 percent carbs, while a 70 kg adult bulking on 3000 calories with the same 1.6 g/kg protein lands closer to 15 percent protein and 65 percent carbs.
How much protein do I need to build muscle?
The 2018 meta-analysis by Morton and colleagues in the British Journal of Sports Medicine pooled 49 randomized controlled trials and 1,863 participants. Gains in muscle mass and strength plateaued at roughly 1.62 g/kg of body weight per day, with a 95 percent confidence interval of 1.03 to 2.20 g/kg. We default intermediate trainees to 1.8 g/kg and advanced trainees in a deficit to 2.2 g/kg, both within that established window. For a more focused breakdown by goal alone, see our protein calculator.
Do I really need to count carbs?
You do not need to count every gram, but you do need a rough target so you can hit your calorie goal without short-changing protein or fat. Carbs are the most flexible macro because they are not bound by a hormonal-health minimum or a muscle-protein-synthesis ceiling. Set protein and fat first based on body weight, then carbs are simply whatever calories are left. For most healthy adults, that lands between 40 and 60 percent of total calories, which lines up with the typical ranges cited in the 2017 ISSN position stand on diets and body composition (Aragon et al.).
What is a safe calorie deficit for cutting?
A 15 to 20 percent deficit below maintenance is the sustainable range for most adults trying to lose fat while preserving muscle. The Helms et al. 2014 contest-prep paper notes that aggressive deficits beyond 25 percent accelerate lean mass loss, drop training performance, and disrupt hormones, especially when body fat is already low. The calculator caps the cut at 25 percent and warns when you are at the aggressive end. For very lean athletes near contest condition, a registered sports dietitian is a better partner than any generic tool.
How much fat should I eat per day?
The 2017 ISSN diet review (Aragon et al.) puts the practical floor at 0.6 g/kg of body weight per day. The Helms et al. 2014 contest-prep paper recommends a slightly higher 0.8 g/kg as a sensible default for hormonal health, especially during a cut. We default to 0.8 g/kg and let advanced users adjust. Below about 20 percent of total calories from fat, sex hormones (testosterone in men, menstrual function in women) start to take a measurable hit, so dropping fat too low to leave room for carbs is a bad trade.
Do older adults need more protein?
Yes. The PROT-AGE consensus paper (Bauer et al. 2013) recommends a floor of 1.0 to 1.2 g/kg of body weight per day for healthy adults over 65, and 1.2 to 1.5 g/kg for those with acute or chronic disease. Older adults trying to preserve or build muscle through resistance training should aim for 1.2 to 1.6 g/kg. The calculator enforces a 1.6 g/kg minimum for adults 65 and older even in the sedentary band, because anabolic resistance means a higher dose is needed for the same muscle-protein-synthesis response.