Finding your macros is a three-step process: estimate how many calories your body needs each day, decide what percentage of those calories should come from protein, carbs, and fat, then convert those percentages into grams. The whole calculation takes about five minutes once you know the formula.
Step 1: Estimate Your Daily Calories
Before you can split calories into macros, you need a calorie target. That starts with your basal metabolic rate (BMR), the number of calories your body burns at complete rest just to keep your organs running, your lungs breathing, and your brain functioning. The most reliable formula for estimating BMR is the Mifflin-St Jeor equation, which a systematic review in the Journal of the American Dietetic Association found predicted resting metabolic rate within 10% of measured values more consistently than competing formulas.
Here’s the math:
- Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
If you think in pounds and inches, multiply your weight in pounds by 0.453 to get kilograms, and your height in inches by 2.54 to get centimeters. For example, a 35-year-old woman who weighs 150 pounds (68 kg) and stands 5’6″ (167.6 cm) would calculate: (10 × 68) + (6.25 × 167.6) – (5 × 35) – 161 = 1,393 calories at rest.
Your BMR only covers survival. To account for how much you actually move during the day, multiply it by an activity factor:
- Sedentary (desk job, little exercise): BMR × 1.2
- Lightly active (light exercise 1–3 days/week): BMR × 1.375
- Moderately active (moderate exercise 3–5 days/week): BMR × 1.55
- Very active (hard exercise 6–7 days/week): BMR × 1.725
- Extremely active (intense training plus physical job): BMR × 1.9
Using the example above, if that woman exercises moderately three to five days per week, her total daily energy expenditure (TDEE) is roughly 1,393 × 1.55 = 2,159 calories. That’s her maintenance number. To lose fat, she’d subtract 250 to 500 calories. To gain muscle, she’d add 200 to 300. Most people overestimate their activity level, so when in doubt, round down.
Step 2: Choose Your Macro Split
Every gram of each macronutrient delivers a fixed amount of energy: protein has 4 calories per gram, carbohydrates have 4 calories per gram, and fat has 9 calories per gram. (Alcohol, for reference, has 7 calories per gram and no nutritional benefit, which is worth remembering if drinks are part of your week.) These numbers are what let you convert a calorie target into actual grams of food.
The U.S. Dietary Guidelines, based on ranges set by the National Academies of Sciences, suggest broad windows for healthy adults: roughly 10–35% of calories from protein, 45–65% from carbohydrates, and 20–35% from fat. Those ranges are wide on purpose. Where you land within them depends on your goal.
For Fat Loss
Protein becomes the priority. When you’re eating fewer calories than you burn, higher protein intake protects your muscle mass so the weight you lose comes primarily from fat. A common recommendation for weight loss is 1.0 to 1.2 grams of protein per kilogram of body weight per day. For someone weighing 68 kg, that’s 68 to 82 grams. Many coaches push toward the higher end, especially if you’re strength training alongside a deficit. A practical starting split for fat loss is 30% protein, 35% carbs, and 35% fat, then adjusted based on how you feel and perform.
For Muscle Gain
Research aggregating data across men, women, and various ages suggests that 1.6 to 2.2 grams of protein per kilogram of body weight per day optimizes muscle building. For someone at 68 kg, that’s 109 to 150 grams of protein daily. Carbs matter here too, because they fuel the intense training that drives muscle growth. A typical muscle-gain split might be 30% protein, 45% carbs, and 25% fat.
For General Health
If you’re not chasing a specific physique goal, a balanced split like 25% protein, 45% carbs, and 30% fat works well for most people. The key is consistency and eating enough fiber. The current recommendation is 14 grams of fiber per 1,000 calories you eat, so a 2,000-calorie diet calls for about 28 grams. Hitting that number naturally steers your carbohydrate choices toward whole grains, vegetables, and fruit rather than refined sugars.
Step 3: Convert Percentages to Grams
This is where the numbers become a meal plan. Take your calorie target, apply your percentage split, then divide by the calories per gram for each macro. Here’s a worked example for a person eating 2,000 calories on a 30/40/30 split (protein/carbs/fat):
- Protein: 2,000 × 0.30 = 600 calories ÷ 4 = 150 grams
- Carbs: 2,000 × 0.40 = 800 calories ÷ 4 = 200 grams
- Fat: 2,000 × 0.30 = 600 calories ÷ 9 = 67 grams
Those three numbers are your daily targets. You don’t need to hit them exactly. Landing within 5 to 10 grams on protein and carbs, and within 3 to 5 grams on fat, is close enough to get results over time.
How to Spread Protein Through the Day
Your body can digest and absorb large amounts of protein in one sitting, but the muscle-building signal peaks at a lower threshold. Research suggests that 20 to 25 grams of protein per meal maximizes the muscle-building response in a single sitting for most people. Beyond that, the protein still gets used for energy and other functions, but the muscle-specific benefit plateaus. The practical takeaway: spreading your total protein target across four meals, at roughly 0.4 to 0.55 grams per kilogram per meal, is more effective for building or preserving muscle than cramming it all into one or two large meals.
For someone weighing 68 kg eating 150 grams of protein, that’s about 37 grams across four meals. A chicken breast, a scoop of protein powder, a cup of Greek yogurt, or a can of tuna each delivers roughly that amount.
Tracking Your Macros in Practice
Knowing your numbers is one thing. Actually hitting them requires logging what you eat, at least initially. A food scale and a tracking app make this realistic. Among the most popular options, MyFitnessPal is widely considered the best dedicated macro counter, with a large food database that tracks calories, protein, carbs, fat, fiber, sugar, and sodium. Cronometer stands out as the best free option and goes deeper into micronutrients like vitamins and minerals, with barcode scanning available even without paying. Both apps let you set custom macro targets in grams.
Most people find that after two to three weeks of consistent logging, they develop an intuitive sense of portion sizes and can estimate with reasonable accuracy without weighing every ingredient. The early discipline of tracking pays off as a long-term education in what’s actually in your food.
Adjusting When Your Numbers Aren’t Working
Your calculated macros are a starting point, not a final answer. The formulas estimate average metabolic rates, but individual variation is real. If after two to three weeks you’re not seeing the changes you expected (scale not moving, energy tanking, performance dropping), the fix is usually small.
For fat loss stalls, reduce carbs or fat by 50 to 100 calories (about 12 to 25 grams of carbs or 6 to 11 grams of fat) rather than slashing everything at once. Keep protein steady or increase it slightly. For low energy during workouts, add 25 to 50 grams of carbs around your training window and see if performance improves.
Certain health conditions also shift the picture. People with insulin resistance or polycystic ovary syndrome (PCOS), for example, often do better choosing low-glycemic carbohydrates like fiber-rich whole grains and non-starchy vegetables, and eating smaller meals roughly every four hours to keep blood sugar stable. This doesn’t mean eliminating carbs, just being more selective about the type and timing. If you have a metabolic condition that affects how your body processes any macronutrient, your targets will look different from the standard formulas.
Reassess your macros every four to six weeks, or whenever your weight changes by more than 5 to 10 pounds, your activity level shifts significantly, or your goals change. The calculation is the same each time. The only numbers that change are the inputs.