Finding your macros is a three-step process: estimate how many calories your body burns each day, decide how to split those calories between protein, carbs, and fat based on your goal, then convert those percentages into grams. The whole calculation takes about five minutes once you understand the logic behind it.
Step 1: Estimate Your Daily Calories
Before you can divide calories into macros, you need to know roughly how many calories your body uses in a day. This number, called your total daily energy expenditure (TDEE), combines two things: the calories your body burns just to keep you alive (breathing, digesting, maintaining body temperature) and the calories you burn through movement and exercise.
The most widely used formula for that baseline calorie burn is the Mifflin-St Jeor equation. You’ll need your weight in kilograms, height in centimeters, and age in years. To convert pounds to kilograms, divide by 2.2. To convert inches to centimeters, multiply by 2.54.
- For men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- For women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
That gives you your basal metabolic rate, or BMR. A 35-year-old woman who weighs 150 pounds (68 kg) and stands 5’6″ (167.6 cm), for example, would calculate: (10 × 68) + (6.25 × 167.6) − (5 × 35) − 161 = 1,392 calories.
Next, multiply your BMR by an activity factor to account for how much you move:
- Sedentary (desk job, no planned exercise): multiply by 1.2
- Lightly active (light exercise 1 to 3 days per week): multiply by 1.375
- Moderately active (moderate exercise 3 to 5 days per week): multiply by 1.55
- Very active (hard exercise 6 to 7 days per week): multiply by 1.725
- Extremely active (intense training plus a physical job): multiply by 1.9
If that same woman exercises moderately three to five days a week, her TDEE would be roughly 1,392 × 1.55 = 2,158 calories. That’s her estimated maintenance intake, the number of calories that would keep her weight stable. Most people should pick the activity level that honestly reflects a typical week rather than their best week.
Step 2: Adjust Calories for Your Goal
Your TDEE is the starting line. What you do next depends on whether you want to lose fat, build muscle, or maintain your current weight.
For fat loss, a common approach is to subtract 300 to 500 calories from your TDEE. Larger deficits can speed things up but also make it harder to hold onto muscle and stick with the plan long term. For muscle gain, adding 200 to 300 calories above your TDEE gives your body the extra energy it needs to build new tissue without excessive fat gain. For maintenance, your TDEE itself is your target.
Step 3: Choose Your Macro Split
Now you divide your adjusted calorie target into protein, carbohydrates, and fat. Each gram of protein and carbohydrate provides 4 calories. Each gram of fat provides 9 calories. That difference is why fat takes up a smaller percentage of your plate but still contributes a big chunk of your calories.
The U.S. Dietary Guidelines set broad acceptable ranges for adults: 45 to 65% of calories from carbs, 10 to 35% from protein, and 20 to 35% from fat. Within those ranges, your specific goal shapes where you land.
For Weight Loss
A solid starting point is 25 to 35% protein, 40 to 50% carbs, and 20 to 30% fat. The higher protein end helps preserve muscle while you’re in a calorie deficit and keeps you feeling full longer. Using our example of a woman targeting about 1,700 calories for fat loss, a 30/45/25 split would look like: 510 calories from protein (128 g), 765 calories from carbs (191 g), and 425 calories from fat (47 g).
For Muscle Gain
Aim for 25 to 35% protein, 45 to 55% carbs, and 15 to 25% fat. The extra carbohydrates fuel hard training sessions and support recovery. If that same woman were eating 2,450 calories for a muscle-building phase, a 30/50/20 split would give her 184 g protein, 306 g carbs, and 54 g fat.
For Maintenance
A typical maintenance split runs 25 to 30% protein, 55 to 60% carbs, and 15 to 20% fat. This is more flexible since you’re not pushing toward a specific body composition change. The 40/40/20 split (40% protein, 40% carbs, 20% fat) is another popular option for people who want a simpler ratio to remember, though it runs higher on protein than most people strictly need.
How to Convert Percentages to Grams
The math is straightforward once you have your calorie target and your chosen percentages. Here’s the formula for each macro:
- Protein grams: (total calories × protein percentage) ÷ 4
- Carb grams: (total calories × carb percentage) ÷ 4
- Fat grams: (total calories × fat percentage) ÷ 9
For someone eating 2,000 calories on a 30/45/25 split, that works out to 150 g protein, 225 g carbs, and 56 g fat. Those are the daily gram targets you’d actually track.
Protein and Fat Minimums Worth Knowing
Regardless of which ratio you choose, there are floors you don’t want to drop below. The absolute minimum protein intake for general health is 0.8 grams per kilogram of body weight (about 0.36 grams per pound). That’s the amount needed to prevent deficiency, not to optimize anything. Most people focused on fitness or body composition do better at 1.2 to 2.0 grams per kilogram.
Fat has a similar minimum. Your body needs dietary fat to produce hormones, absorb vitamins, and maintain cell membranes. A general guideline for hormonal health is at least 0.8 to 1.0 grams of fat per kilogram of body weight. For a 150-pound person, that’s roughly 55 to 68 grams of fat per day. Dropping well below that range, especially for extended periods, can disrupt hormone levels.
Tracking Your Macros Accurately
Knowing your numbers only matters if you can reasonably track them. A digital food scale is the single most useful tool. Volume measurements (cups, tablespoons) introduce surprising variability. A cup of flour can differ by as much as three tablespoons depending on whether it was spooned in, scooped, or packed down. A teaspoon of granular salt can contain twice as much salt as a teaspoon of flake salt. Weight is a direct measurement of the food itself, while volume measures a combination of food and empty space.
You don’t need to weigh everything forever. Most people find that after a few weeks of consistent weighing, they develop a strong visual sense of portion sizes and only need the scale occasionally to recalibrate. Apps like MyFitnessPal or Cronometer let you scan barcodes or search foods and automatically tally your protein, carbs, and fat as you log meals throughout the day.
Total Carbs vs. Net Carbs
If you follow a lower-carb approach, you’ll run into the term “net carbs.” The calculation is simple: total carbohydrates minus fiber minus sugar alcohols. The reasoning is that fiber and sugar alcohols don’t raise blood sugar the way other carbohydrates do, so they’re subtracted from the total. A food with 24 grams of total carbs but 10 grams of fiber and 8 grams of sugar alcohols would have just 6 net carbs.
For most people tracking standard macro splits, total carbs is the more straightforward number to use. Net carbs become more relevant if you’re following a ketogenic diet or managing blood sugar carefully.
Fine-Tuning Over Time
Your calculated macros are an educated starting point, not a final answer. Bodies vary, and formulas can’t account for individual differences in metabolism, stress, sleep quality, or how your body partitions nutrients. Give any set of macros at least two to three weeks before making changes. Track your weight, energy levels, and workout performance. If your weight isn’t moving in the direction you want after that initial period, adjust calories by 100 to 200 per day rather than overhauling everything at once. Small shifts are easier to sustain and make it clearer what’s actually working.
Your macros will also need to shift as your body changes. Someone who loses 20 pounds will have a lower TDEE simply because there’s less body mass to fuel. Recalculating every 10 to 15 pounds of change, or every couple of months, keeps your numbers aligned with your actual needs.