Macro Calculator
A macro calculator turns your body stats into daily gram targets for protein, carbohydrates, and fat. This one estimates your resting burn with the Mifflin-St Jeor equation, or with Katch-McArdle when you enter a body fat percentage, scales it by your activity level, adjusts it by a flat 500 kcal if you want to lose or gain, then splits the calories with protein set per kilogram of body weight, fat as a fixed share, and carbs filling the rest. Targets are floored: never below resting burn, and never below 1,200 kcal for women or 1,500 kcal for men without medical supervision. It also gives per-meal targets, a fiber and water target, and an optional training-day carb split, in imperial or metric units.
Daily calorie target
| Protein | |
| Carbohydrates | |
| Fat | |
| BMR (resting burn) | |
| TDEE (maintenance calories) | |
| Fiber target | |
| Water target | |
| Per meal |
Estimates only. Mifflin-St Jeor predicts resting burn within about 10% for most people; Katch-McArdle, from lean mass, suits very muscular or very lean users who know their body fat percentage. Targets are floored at resting burn and at 1,200 kcal for women or 1,500 kcal for men. Adjust after 2 to 3 weeks based on how your weight actually trends.
Quick Answer
For the pre-filled example (man, 30, 180 lb, 5 ft 10 in, moderately active, maintaining, Balanced split) the target is 2,763 kcal a day: 180 g protein, 338 g carbs, and 77 g fat, from a BMR of 1,783 kcal and a TDEE of 2,763 kcal. The same stats on Lose return 2,263 kcal (180 g / 245 g / 63 g) and on Gain return 3,263 kcal (180 g / 432 g / 91 g), because the goal step is a flat 500 kcal either way and protein is fixed by body weight, so only carbs and fat move.
Key takeaways
- Protein is set first, per kilogram of body weight. Fat takes a fixed share of calories. Carbs get whatever is left, which is why carbs swing the most when you change goal or split.
- The goal adjustment is a flat 500 kcal, not a percentage, and a calorie floor applies: no target drops below resting burn, or below 1,200 kcal for women and 1,500 kcal for men without medical supervision. The old unfloored run that printed 542 kcal now floors to 1,200 kcal.
- This tool offers both Mifflin-St Jeor and Katch-McArdle: pick Katch-McArdle and enter a body fat percentage to estimate resting burn from lean mass instead of total weight.
- Training-day carb cycling moves carbs between days without changing your week: the seven days still average your daily target.
- Quick Answer
- How to use the macro calculator
- The formula, and every hard-coded factor in it
- Worked example: 30, 180 lb, 5 ft 10 in, moderately active
- The four split styles, on the same body
- Per-meal targets and training-day carb cycling
- General macros are not bodybuilding macros
- What competing calculators miss
- Frequently asked questions
- Add This Calculator to Your Website
How to use the macro calculator
Enter your stats, pick an activity level and a goal, and click Calculate. Results stay hidden until you calculate, and every result includes the step-by-step arithmetic so you can check it.
- Units: stay in Imperial for pounds and feet-and-inches, or switch to Metric for kilograms and centimeters. The two modes convert the same body two ways; the worked example in Metric (80 kg, 178 cm) returns 2,740 kcal, close to but not identical to the Imperial run because 180 lb is 81.6 kg, not 80 kg.
- Sex, age, weight, height: these four feed Mifflin-St Jeor directly. Age must be 10 to 100 and weight must be above zero or the tool stops with a message.
- Activity level: pick on your whole week. Overpicking this one setting is the most common reason a target misses, because it multiplies everything else.
- Goal: Lose is maintenance minus 500 kcal, Gain is maintenance plus 500 kcal. At roughly 3,500 kcal per pound of body fat, a 500 kcal daily step is the classic one-pound-a-week pace in either direction.
- Split style: choose how protein and fat are set. Your carbohydrate target is never set directly here; it is always the remainder after protein and fat, which is worth understanding before you judge the carb number.
- Meals and training days: meals only divide the daily grams into per-meal lines. Training days are optional: set 1 to 6 if you want the carb-cycling split explained below, or leave at 0.
The formula, and every hard-coded factor in it
BMR comes from Mifflin-St Jeor, TDEE is BMR times an activity factor, and the split is protein per kilogram, then a fat share, then carbs as the remainder. Nothing in this tool is fitted to you beyond those steps, and every constant it uses is listed here.
BMR (women) = 10 weight (kg) + 6.25 height (cm) 5 age 161
TDEE = BMR activity factor (1.2 / 1.375 / 1.55 / 1.725 / 1.9)
Calorie target = TDEE 500 (Lose), TDEE (Maintain), or TDEE + 500 (Gain)
Protein (g) = weight (kg) split rate | Fat (g) = target fat share 9 | Carbs (g) = (target protein 4 fat 9) 4, never below 0
The equation itself is the 1990 Mifflin-St Jeor equation published in the American Journal of Clinical Nutrition, and reviews since then, including the Frankenfield comparison studies, have kept it as the best-validated weight-and-height predictor of resting burn for general adults. The protein rates sit at or above the range the International Society of Sports Nutrition supports for exercising people, and the fiber rule (14 g per 1,000 kcal) is the Institute of Medicine basis behind the FDA Daily Value. Two honest limits belong next to the formula, plus the fix that removes the third. First, the Katch-McArdle path (BMR = 370 + 21.6 times lean body mass) needs a body fat percentage you have actually measured: if you guess it, the lean mass estimate is only as good as the guess, and for most people Mifflin-St Jeor remains the safer default. Second, the 500 kcal goal step is flat, so it is a large cut for a small person and a mild one for a large person; percentage-based rivals behave the opposite way. The fix: there is now a calorie floor. No Lose target falls below resting burn, or below 1,200 kcal for women and 1,500 kcal for men without medical supervision, and the split protects a 50 g carb minimum by trimming fat, then protein, toward their floors before carbs are allowed below 50 g.
Worked example: 30, 180 lb, 5 ft 10 in, moderately active
The pre-filled run maintains weight on the Balanced split. Here is every line the tool returns, verified against the code.
| Line | Value | How it arises |
|---|---|---|
| BMR | 1,783 kcal | 10 81.6 + 6.25 178 5 30 + 5 |
| TDEE | 2,763 kcal | 1,783 1.55 |
| Protein | 180 g (720 kcal) | 81.6 kg 2.2 g/kg |
| Fat | 77 g (693 kcal) | 2,763 25% 9 |
| Carbs | 338 g (1,352 kcal) | (2,763 720 693) 4 |
| Calorie shares | 26% / 49% / 25% | Shares of the rounded grams, as the bar shows |
| Per meal (3 meals) | 60 g / 113 g / 26 g | Each daily target divided by 3 |
Two edge runs show where the tool’s rules bite. A sedentary 35-year-old woman at 150 lb and 5 ft 5 in on Lose gets 1,152 kcal with 150 g protein, 66 g carbs, and 32 g fat: protein alone is 52% of that target, because protein follows body weight while the budget shrank by the flat 500. Push further (60 years old, 90 lb, 4 ft 10 in, sedentary, Lose, Lower carb) and the tool returns 542 kcal with carbs clamped to 0 g, because protein (360 kcal) plus fat (216 kcal) already exceed the 542 kcal budget. The clamp keeps the answer usable, but a target like that is a prompt to get professional guidance, not a diet plan.
The four split styles, on the same body
All four splits below are the same worked example at 2,763 kcal. Only the protein rate and fat share change; carbs absorb the whole difference.
| Split | Protein rule | Fat share | Protein | Carbs | Fat |
|---|---|---|---|---|---|
| Balanced | 2.2 g/kg | 25% | 180 g | 338 g | 77 g |
| High protein | 2.6 g/kg | 30% | 212 g | 271 g | 92 g |
| Lower carb | 2.2 g/kg | 40% | 180 g | 235 g | 123 g |
| Higher carb | 1.8 g/kg | 20% | 147 g | 406 g | 61 g |
Carbs by split, grams per day (same 2,763 kcal target)
Note what Lower carb means here: 235 g of carbs is lower than the other splits, but it is not a ketogenic target. Fat share is the lever, and at 40% it still leaves a substantial carb remainder at most calorie levels. If you are gaining, the Gain run on this body (3,263 kcal, 432 g carbs on Balanced) is the starting point a dedicated bulking calories plan builds on with meal timing and progression.
Per-meal targets and training-day carb cycling
Daily grams are only half the plan; the other half is how you split them across meals and across the week. Set training days to 4 on the worked example and the tool returns training days at 3,105 kcal (180 g protein, 423 g carbs, 77 g fat) and rest days at 2,313 kcal (180 g protein, 225 g carbs, 77 g fat).
The cycling math is constrained, not decorative. Training-day carbs are 125% of the daily target, and rest-day carbs are solved from the weekly budget: (7 338 4 423) 3 = 225 g, so the week still averages 338 g of carbs a day. If that solution would push rest days under 25% of the daily target, the tool lowers the training bump instead and pins rest days at the 25% floor: at 6 training days the split becomes 380 g on training days and 85 g on the single rest day. Protein and fat never cycle, which matches how most people actually eat: same protein anchor every day, carbs doing the flexing. Two quirks are worth knowing. Entering 7 training days just returns the daily targets with a note, and entering 8 or more does the same, because the tool treats anything at or above 7 as a full training week. And the per-meal line always divides the daily targets, never the training-day ones, so on a cycling plan you still split each day type by hand.
General macros are not bodybuilding macros
This page is the general macro calculator: it serves anyone setting a first protein, carb, and fat target for losing, maintaining, or gaining. Bodybuilding macro tools aim at a narrower job, and the method differences matter more than the labels.
- Protein base: this tool sets protein on total body weight (1.8 to 2.6 g/kg). Bodybuilding tools usually set it on lean body mass, which gives lean, heavy lifters a lower and more realistic number.
- BMR equation: this tool is Mifflin-St Jeor only. Bodybuilding tools usually offer Katch-McArdle once you enter body fat percentage, because stage-lean athletes are exactly the people Mifflin-St Jeor fits worst. Your fat-free mass index tells you whether you are in that group.
- Goal sizing: this tool uses one flat 500 kcal step for everyone. Contest-prep tools size the deficit as a percentage of body weight per week and taper it, because a flat 500 is reckless at low body fat.
- Extras: no refeed days, no peak-week logic, no sodium or water manipulation here. If you need those, you are past general macros and into prep coaching territory.
Neither approach is wrong; they answer different questions. Start here if you do not know your body fat percentage and your goal is general fat loss, maintenance, or a steady gain. Move to a lean-mass method when you have a credible body fat measurement and enough muscle that total-weight protein looks inflated.
What competing calculators miss
Most rival macro calculators agree on Mifflin-St Jeor and then diverge in ways they rarely explain. The ones checked for this page fall into clear patterns:
- Percentage-split tools (SmartOnlineCalculator, AJDesigner, BoldCalc): they split calories by fixed percentages (30/40/30 and similar) and adjust goals by percentages (15% or 20% cuts, 10 to 15% surpluses). Clean, but protein then rises and falls with calories instead of tracking body weight, and none shows per-meal or training-day splits.
- Katch-McArdle tools (Fitness Volt, MrCalcu, Macronutrients.com): genuinely better for lean users who know their body fat, with calorie floors (1,200 kcal for women, 1,500 for men on Fitness Volt) this tool lacks. The cost is an input most people guess badly: a wrong body fat entry quietly poisons every output.
- Simple per-pound tools (EatSleepRep, CTWorkout): protein at 1 g per pound is memorable, and CTWorkout adds a goal-weight option and floors. Neither converts units both ways with a full step breakdown, and neither cycles carbs between training and rest days.
- The gap this page fills: protein anchored to body weight in kilograms, fat as an explicit share, carbs as an honest remainder, a full step list under every result, and a carb-cycling split whose weekly average is guaranteed by construction. Its weaknesses are stated on this page rather than hidden: a flat 500 kcal goal step, and estimates that are only as good as the body fat percentage you enter on the Katch-McArdle path.
Frequently asked questions
Macros are the three macronutrients that supply your calories: protein at 4 kcal per gram, carbohydrates at 4 kcal per gram, and fat at 9 kcal per gram. Alcohol also supplies energy at 7 kcal per gram, but it is not a macronutrient target.
For active people, research supports roughly 1.6 to 2.2 grams per kilogram of body weight per day, with the higher end helping to protect muscle during a calorie deficit. The Balanced split in this calculator uses 2.2 g per kg, and the High protein split uses 2.6 g per kg.
It is a 1990 equation for basal metabolic rate that validation studies found more accurate than the older Harris-Benedict equation for most modern adults. It needs only weight, height, age, and sex, which is why most macro calculators use it as their starting point.
Use Katch-McArdle when you know your body fat percentage and you are very lean or very muscular, because it estimates resting burn from lean body mass (370 plus 21.6 times lean mass in kilograms) instead of charging full price for every kilogram including fat. For most people, Mifflin-St Jeor remains the default: it needs only weight, height, age and sex. Pick Katch-McArdle in the method menu and enter a body fat percentage between 3 and 60.
Usually no. Your activity level selection already accounts for typical training, and trackers often overestimate exercise burn, so eating the full amount back tends to erase a deficit. If you train far beyond the activity level you picked, raise the activity level instead.
No target is automatically safe. This tool subtracts a flat 500 kcal, but a calorie floor now applies: no target drops below resting burn, or below 1,200 kcal for women and 1,500 kcal for men without medical supervision. The old unfloored run that returned 542 kcal now floors to 1,200 kcal. Treat very low results as a signal to talk to a clinician or dietitian, not as a plan.
Training days get 25 percent more carbs and rest days get proportionally fewer, solved so the seven days still average your daily carb target. Rest-day carbs never drop below 25 percent of the daily target, and protein and fat stay constant because daily protein matters more than timing.
It means protein and fat alone already meet or exceed your calorie target at those settings, so the remainder for carbs is negative. The tool first trims fat, then protein, toward their floors to protect a 50 g carb minimum, and only shows 0 g when even that cannot fit the target. The step list still shows the subtraction. Raise the calorie target, or pick a split with less protein or fat, to bring carbs back above zero.
Give any target 2 to 3 weeks, track morning weigh-ins, and compare weekly averages rather than daily numbers. If the trend is flat, adjust by 200 to 300 kcal, not by overhauling everything at once.
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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. American Journal of Clinical Nutrition, 1990. Accessed October 22, 2026.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association, 2005. Accessed October 22, 2026.
- Jager R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition position stand: protein and exercise. Journal of the International Society of Sports Nutrition, 2017. Accessed October 22, 2026.
- 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. British Journal of Sports Medicine, 2018. Accessed October 22, 2026.
- Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition, 2014. Accessed October 22, 2026.
- U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. Accessed October 22, 2026.
- World Health Organization. Healthy diet fact sheet. Accessed October 22, 2026.
- U.S. Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels. Accessed October 22, 2026.
- National Institute of Diabetes and Digestive and Kidney Diseases. Weight Management health information. Accessed October 22, 2026.
- Cunningham JJ. Body composition as a determinant of energy expenditure: a reanalysis of the Katch-McArdle approach. American Journal of Clinical Nutrition, 1991. Accessed October 22, 2026.
- McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance. Wolters Kluwer. The source of the Katch-McArdle equation: resting burn equals 370 plus 21.6 times lean body mass in kilograms. Accessed October 24, 2026.
- National Heart, Lung, and Blood Institute. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. National Institutes of Health. The basis for the calorie floor convention used here: intakes below 1,200 kcal a day for women and 1,500 kcal a day for men are not undertaken without medical supervision. Accessed October 24, 2026.