Why use this calculator
Calories decide whether your weight moves and macros decide what that weight is made of. Two people eating the same 2,000 calories can lose very different amounts of muscle, because protein intake and training are what protect lean mass while energy is short. This calculator anchors protein to your body weight rather than to a percentage of calories, which is the part most macro tools get wrong: a percentage split gives a small person on a low intake far too little protein and a large person on a high intake far more than they can use.
It then sets fat at a share that keeps hormones and satiety in reasonable shape and puts the remaining energy into carbohydrate, which is the macro that fuels training. You get grams you can actually shop and cook against, plus the maintenance figure to compare them with.
How to use it
- Pick metric or imperial first, because the weight and height fields change with it.
- Enter your weight measured first thing in the morning before eating, since food and fluid move the scale by one to two kilograms across a single day.
- Enter your height measured against a wall without shoes rather than the number you remember.
- Enter your age in whole years, as resting metabolism declines steadily from your twenties.
- Choose your sex, which sets the constant in the Mifflin-St Jeor equation.
- Choose the activity level that matches a normal week rather than your best week, and if you sit between two options take the lower one.
- Choose your goal, then choose how far from maintenance you want to sit, remembering that the aggressive option is only sensible if you have a lot to lose.
What each result means
- Daily Calorie Target
- The energy intake to aim for each day given your goal. Treat it as a two-week hypothesis to test against your weight trend, not a fixed number.
- Maintenance (TDEE)
- The calories that should hold your weight steady at the activity level you selected. Everything else on this page is measured against it.
- Basal Metabolic Rate
- Energy your body spends at complete rest running organs, holding temperature and repairing tissue. Eating below it for long is difficult to do safely.
- Protein
- Grams of protein a day, anchored to your body weight. This is the macro that protects muscle while you are in a calorie deficit.
- Carbohydrates
- Grams of carbohydrate a day, taking whatever energy is left after protein and fat. This is the macro that fuels hard training.
- Fat
- Grams of fat a day. Dropping much below about 0.5 g per kilogram of body weight tends to hurt hormones, satiety and food enjoyment.
- Protein per kg of body weight
- Your protein target expressed per kilogram, so you can compare it against the 1.6 to 2.2 g range used in sports nutrition guidance.
- Protein per lb of body weight
- Your protein target expressed per pound, so you can compare it against the familiar 0.7 to 1.0 g per pound rule of thumb.
- Predicted Weekly Weight Change
- What the energy arithmetic predicts each week, using 3,500 kcal per pound or 7,700 per kilogram of body fat. Real results usually run slower.
The formula
Resting metabolic rate uses the Mifflin-St Jeor equation: BMR in kcal per day equals 10 x weight in kilograms plus 6.25 x height in centimetres minus 5 x age in years, then plus 5 for men or minus 161 for women. Total daily energy expenditure is BMR multiplied by an activity factor of 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 very active or 1.9 extra active. The calorie target is TDEE minus 250, 500 or 750 kcal when cutting, TDEE plus the same when gaining, and never below your BMR. Protein in grams is body weight in kilograms multiplied by 2.2 when cutting, 1.8 at maintenance or 1.9 when gaining. Fat in grams is 30 per cent of target calories divided by 9 (25 per cent when gaining). Carbohydrate takes the remaining energy divided by 4. The Atwater factors are 4 kcal per gram of protein, 4 per gram of carbohydrate and 9 per gram of fat.
How this number is used in practice
The first place a macro plan meets reality is the supermarket. A 170 g protein target sounds abstract until you translate it: roughly 200 g of chicken breast, a 170 g tin of tuna, a tub of Greek yoghurt and two eggs get you most of the way there, and a scoop of whey covers the shortfall.
The same goes for fat, where two tablespoons of olive oil and half an avocado is already 50 g. Most people who fail a macro plan do not fail on willpower, they fail because they never worked out what the numbers look like on a plate, and a target that cannot be assembled from food you actually buy will not survive a fortnight.
The second place it meets reality is the scale, and the honest answer is that the equation is only a starting point. Mifflin-St Jeor predicts measured resting metabolic rate within about ten per cent for most adults, which on a 2,700 kcal maintenance figure is a range of nearly 550 calories.
Activity multipliers add more error than the equation itself. Adjust on the evidence instead: hold the target for two to three weeks, compare weekly average weight rather than single weigh-ins, and move by 150 to 250 calories if the trend is not doing what you want.
Anyone who is pregnant or breastfeeding, under 18, managing diabetes, kidney disease or an eating disorder, or taking medication that affects appetite or metabolism should get an individual plan from a dietitian or doctor rather than using a population equation.
Worked examples
30 year old male, 170 lb, 70 in, moderately active, losing fat on a 500 kcal deficit
2,193 kcal a day with 170 g protein, 214 g carbohydrate and 73 g fat, against a maintenance figure of 2,693 kcal.
40 year old female, 62 kg, 165 cm, lightly active, maintaining weight
1,774 kcal a day with 112 g protein, 199 g carbohydrate and 59 g fat, at 1.8 g of protein per kilogram.
25 year old male, 200 lb, 72 in, very active, gaining on a 500 kcal surplus
3,830 kcal a day with 172 g protein, 546 g carbohydrate and 106 g fat, predicting about a pound a week of gain.
When people use it
- Setting protein, carb and fat targets for a fat loss phase without losing muscle
- Working out how much food a gaining phase actually requires before starting it
- Checking whether a coach or app has set your protein target in a sensible range
- Rebuilding targets after a change in training volume, job or body weight
- Splitting a daily target across three or four meals for meal prep
Tips
- Weigh food raw and uncooked for the first fortnight. Cooked weights vary enormously with method and are the single biggest source of tracking error.
- Hit protein first every day. If something has to give, let carbohydrate or fat move rather than protein.
- Judge progress on a weekly average of daily weigh-ins, never on one reading. Day-to-day swings of one to two kilograms are water and gut contents.
- Recalculate after every 5 kg of weight change, because a lighter body needs less energy simply to exist.
- Leave the aggressive deficit alone unless you are carrying a lot of fat and have medical supervision. Fast loss costs muscle.
- Aim for 25 to 40 g of protein per feed across three or four meals rather than one very large serve.
- Add 25 to 35 g of fibre a day inside your carb target. It does more for hunger than any macro ratio.
What it assumes, and where it stops being accurate
- The Mifflin-St Jeor equation is a population regression, accurate to roughly plus or minus 10 per cent for a given individual, and further off for people at the extremes of body composition.
- Activity multipliers are broad bands. Two people who both call themselves moderately active can differ by 400 calories a day.
- Protein is set from total body weight, which overestimates the requirement for people carrying a high body fat percentage. Use lean mass if you know it.
- Predicted weight change assumes 3,500 kcal per pound of fat and ignores adaptive falls in non-exercise movement, so real loss is usually slower.
- It is not valid during pregnancy or breastfeeding, for anyone under 18, or for anyone managing diabetes, kidney disease, thyroid disease or an eating disorder.
- Alcohol supplies 7 kcal per gram and is not included in any macro shown here. Drinks still count against your calorie target.
Terms used on this page
- Macronutrient
- Protein, carbohydrate or fat: the three energy-yielding components of food, supplying 4, 4 and 9 kcal per gram.
- Mifflin-St Jeor equation
- The regression equation used here to estimate resting metabolic rate from weight, height, age and sex.
- TDEE
- Total daily energy expenditure: resting metabolism multiplied by an activity factor, roughly what holds your weight steady.
- Atwater factors
- The energy conversion values of 4 kcal per gram for protein and carbohydrate, 9 for fat and 7 for alcohol.
- Calorie deficit
- Eating less energy than you expend, the condition required for body fat to be lost.
Questions people ask
- How accurate is a macro calculator?
- The calorie figure is accurate to roughly plus or minus 10 per cent for most adults, which on a 2,500 calorie target is a spread of 500 calories. The activity multiplier adds more uncertainty than the equation. Treat the output as a starting hypothesis, hold it for two to three weeks, and adjust on your actual weight trend.
- How much protein do I really need?
- Sports nutrition guidance generally lands between 1.6 and 2.2 grams per kilogram of body weight a day for active people, with the upper end favoured during a calorie deficit to protect muscle. That is roughly 0.7 to 1.0 grams per pound. Sedentary adults need less, but more protein rarely hurts a healthy person and helps with fullness.
- Do I have to hit my macros exactly?
- No. Being within about 10 per cent of each target is enough, and consistency across a week matters far more than precision on any single day. Protein is the one worth chasing most closely. Carbohydrate and fat can move around each other freely as long as total calories stay near the target.
- Why is my carbohydrate number so high or so low?
- Carbohydrate takes whatever energy is left after protein and fat are set, so it absorbs every change you make elsewhere. A big deficit, a high body weight driving a large protein target, or the 30 per cent fat share can all squeeze it. If carbs look too low to train on, reduce the deficit rather than cutting protein.
- What if the scale is not moving after three weeks?
- Change the target by 150 to 250 calories in the direction you want and hold it another fortnight. Before you do, check your tracking: unlogged cooking oils, drinks and weekend meals routinely account for several hundred calories a day. Compare weekly averages, because a single weigh-in can hide a real trend completely.
- Should I count alcohol in my macros?
- It does not fit any macro, but it absolutely counts as energy at 7 calories per gram, close to fat. A standard drink is roughly 100 calories before mixers. The practical approach is to subtract drinks from your carbohydrate allowance for the day and keep protein untouched, since alcohol also blunts muscle protein synthesis.
Use this with
Macronutrient Calculator answers one part of the question. These pick up where it stops: TDEE Calculator, Calorie Calculator, Protein Intake Calculator and BMR Calculator.
Where these figures come from
This calculation is jurisdiction-neutral arithmetic. No country-specific rules are applied.
- Dietary Guidelines for Americans. Acceptable macronutrient distribution ranges
- World Health Organization: healthy diet. Population intake guidance for fats, sugars and fibre
- NIH NIDDK: weight management. Energy balance and realistic rates of weight change
Macronutrient Calculator produces an estimate for general information. It is not financial, tax, medical, legal or engineering advice. read the full disclaimer. Spotted a wrong number? Report it and it gets fixed. The form picks up this calculator and the inputs you used.