Calculating your macros comes down to three steps: estimate how many calories you burn each day, decide on a goal (lose fat, build muscle, or maintain), and then split those calories between protein, carbohydrates, and fat. The whole process takes about five minutes with a calculator, and the numbers you get will be a solid starting point you can fine-tune over time.
Step 1: Estimate Your Daily Calories
Your body burns a baseline number of calories just to keep you alive: breathing, circulating blood, maintaining body temperature. This is your resting metabolic rate (RMR), and the most accurate formula for estimating it is the Mifflin-St Jeor equation, recommended by the Academy of Nutrition and Dietetics.
For men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
For women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
If you think in pounds and inches, convert first. Divide your weight in pounds by 2.2 to get kilograms. Multiply 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 per day at rest.
But you don’t lie still all day. To get your total daily energy expenditure (TDEE), multiply your RMR by an activity factor:
- Sedentary (desk job, little exercise): multiply by 1.2
- Lightly active (exercise 1–3 days per week): multiply by 1.375
- Moderately active (exercise 3–5 days per week): multiply by 1.55
- Very active (hard exercise 6–7 days per week): multiply by 1.725
- Extremely active (intense training plus a physical job): multiply by 1.9
Most people overestimate their activity level. If you work out three times a week but sit at a desk the rest of the time, “lightly active” is more honest than “moderately active.” Using the example above, our 35-year-old woman who exercises three times a week would multiply 1,393 by 1.375, giving her roughly 1,915 calories per day.
Step 2: Adjust Calories for Your Goal
Your TDEE is maintenance, the number of calories that keeps your weight roughly stable. From there, adjust based on what you want:
- Fat loss: Subtract 300 to 500 calories from your TDEE. A 500-calorie deficit translates to about one pound of fat loss per week. Cutting more aggressively tends to sacrifice muscle and energy.
- Muscle gain: Add 300 to 500 calories above your TDEE. This gives your body enough surplus to build new tissue without piling on excessive fat.
- Maintenance: Keep your TDEE as-is.
For the example above, a fat loss target would be roughly 1,415 to 1,615 calories per day. A muscle gain target would be 2,215 to 2,415.
Step 3: Set Your Protein Target
Protein is the macro worth nailing first because it drives muscle retention, recovery, and satiety. The baseline recommendation for sedentary adults is 0.8 grams per kilogram of body weight, but that’s a minimum to prevent deficiency, not an optimal target for someone who exercises.
If you do regular resistance training, aim for 1.4 to 1.8 grams per kilogram of body weight per day. Endurance athletes fall slightly lower, at 1.2 to 1.4 grams per kilogram. For our 68 kg example, that’s roughly 95 to 122 grams of protein daily if she lifts weights.
Protein contains 4 calories per gram. So 110 grams of protein equals 440 calories from protein alone. That number becomes important in the next step.
Step 4: Split Fat and Carbs
Once protein is locked in, divide the remaining calories between fat and carbohydrates. Here’s where personal preference and your style of eating matter most.
Dietary guidelines recommend getting 20% to 35% of your total calories from fat. Fat contains 9 calories per gram, more than double that of protein or carbs, so a little goes a long way. A moderate starting point for most people is around 25% to 30% of total calories from fat.
Carbohydrates also provide 4 calories per gram. After you subtract protein calories and fat calories from your total, everything left over goes to carbs.
Putting It All Together
Let’s walk through the full calculation for our example: a 35-year-old, 150-pound woman aiming for fat loss at 1,500 calories per day.
Protein: 110 grams × 4 calories = 440 calories from protein.
Fat at 25% of total: 1,500 × 0.25 = 375 calories from fat. Divide by 9 to get grams: about 42 grams of fat.
Carbs: 1,500 – 440 – 375 = 685 calories left. Divide by 4: about 171 grams of carbs.
Her daily macros would be roughly 110g protein, 42g fat, and 171g carbs. That’s the number she’d track against food labels or a tracking app.
Common Macro Splits by Goal
If the math feels overwhelming, percentage-based splits give you a quick starting framework. These aren’t universal rules, but they reflect what works for common goals:
- General fitness or maintenance: 30% protein, 25% fat, 45% carbs
- Fat loss with resistance training: 35% protein, 25% fat, 40% carbs
- Muscle gain: 30% protein, 25% fat, 45% carbs (at a caloric surplus)
- Ketogenic diet: 20% protein, 70% fat, 10% carbs
The keto split looks radically different because the entire point is to shift your body’s fuel source from carbohydrates to fat. For most people not following a keto protocol, carbs will remain the largest macro by volume.
Don’t Forget Fiber
Fiber doesn’t get its own macro line, but it deserves attention when you’re planning carb sources. The daily target is based on roughly 14 grams per 1,000 calories you eat. In practice, that works out to about 28 grams per day for most adult women and 31 to 34 grams for most adult men. These numbers decrease slightly after age 50. Prioritizing vegetables, whole grains, legumes, and fruit helps you hit this target naturally.
Why These Numbers Are a Starting Point
Every formula is an estimate. Your actual metabolic rate depends on factors no equation can capture: genetics, muscle mass, sleep quality, stress levels, hormonal fluctuations. The Mifflin-St Jeor equation is the most validated option available, but it can still be off by 10% or more for any individual.
The practical solution is simple. Run the calculation, follow the macros for two to three weeks, and track what happens. If you’re trying to lose fat and the scale hasn’t budged, reduce by another 100 to 200 calories, primarily from carbs or fat (keep protein steady). If you’re trying to gain muscle but feel sluggish and are gaining weight too fast, trim the surplus by 100 to 200 calories. Small adjustments every few weeks are more effective than overhauling your numbers all at once.
Tracking doesn’t need to be permanent, either. Most people find that after a few months of weighing and logging food, they develop a reliable sense of portion sizes and can maintain their macros intuitively. The calculation gives you the map. Experience teaches you the terrain.