Figuring out your macros comes down to three steps: estimate how many calories you need each day, decide what percentage of those calories should come from protein, carbs, and fat, then convert those percentages into grams. The whole process takes about five minutes with a calculator, and the numbers you land on give you a far more useful daily target than calories alone.
Step 1: Estimate Your Daily Calories
Your starting point is your resting metabolic rate (RMR), the number of calories your body burns just to keep you alive. The Academy of Nutrition and Dietetics recommends the Mifflin-St Jeor equation as the most accurate formula for estimating this number:
- Men: (9.99 × weight in kg) + (6.25 × height in cm) − (4.92 × age) + 5
- Women: (9.99 × weight in kg) + (6.25 × height in cm) − (4.92 × age) − 161
To convert pounds to kilograms, divide by 2.2. To convert inches to centimeters, multiply by 2.54. So a 170-pound, 5’10” man who is 30 years old would calculate: (9.99 × 77.3) + (6.25 × 177.8) − (4.92 × 30) + 5, which comes out to roughly 1,740 calories at rest.
That resting number doesn’t account for movement. Multiply it by an activity factor to get your total daily energy expenditure (TDEE):
- Sedentary (desk job, little exercise): RMR × 1.2
- Lightly active (1–3 workouts per week): RMR × 1.375
- Moderately active (3–5 workouts per week): RMR × 1.55
- Very active (6–7 intense sessions per week): RMR × 1.725
Using the example above, a moderately active 30-year-old man would land around 2,700 calories per day. If your goal is fat loss, subtract 300 to 500 calories from that number. If your goal is muscle gain, add 250 to 500. If you want to maintain your current weight, use the number as-is. This is your calorie target, and it becomes the basis for everything that follows.
Step 2: Choose Your Macro Split
Each macro carries a fixed calorie value. Protein and carbohydrates each provide 4 calories per gram, while fat provides 9 calories per gram. These numbers are how you’ll convert percentages into actual grams of food.
The Dietary Guidelines for Americans suggest broad ranges for adults: 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 body and your goals.
For Fat Loss
The single most important factor for losing weight is eating fewer calories than you burn. But within that deficit, a higher protein intake helps you hold onto muscle while you lose fat. Research supports eating 1.2 to 2.0 grams of protein per kilogram of body weight for people aiming to lose weight and preserve lean mass. A practical starting split for fat loss is roughly 30% protein, 40% carbs, and 30% fat. Keeping fat at or above 20% of total calories is important because your body needs dietary fat to absorb certain vitamins and produce hormones.
For Muscle Gain
Building muscle requires a calorie surplus and enough protein to fuel repair. Strength and power athletes generally need 1.4 to 1.8 grams of protein per kilogram of body weight daily. Carbohydrates matter here too, because they replenish the energy stores in your muscles after training. A common starting point is 25–30% protein, 45–55% carbs, and 20–30% fat.
For Endurance Training
Endurance athletes burn through carbohydrates at a high rate. Recommendations for this group range from 6 to 10 grams of carbs per kilogram of body weight daily, depending on training volume. Protein needs are slightly lower than for strength athletes, around 1.2 to 1.4 grams per kilogram. This naturally shifts the ratio toward more carbohydrates and relatively less protein and fat.
Step 3: Convert Percentages to Grams
Once you have a calorie target and a percentage split, the math is straightforward. Take that moderately active man targeting 2,700 calories for maintenance, using a 30/40/30 split:
- Protein (30%): 2,700 × 0.30 = 810 calories ÷ 4 = 203 grams
- Carbs (40%): 2,700 × 0.40 = 1,080 calories ÷ 4 = 270 grams
- Fat (30%): 2,700 × 0.30 = 810 calories ÷ 9 = 90 grams
Those gram targets are what you actually track throughout the day. Most people find it easier to hit a protein target first (since it tends to be the hardest macro to get enough of), then fill in carbs and fat around it.
Use Total Body Weight, Not Lean Mass
You may have seen advice to calculate macros based on lean body mass instead of total body weight. In theory, this makes sense because fat tissue doesn’t need as much protein as muscle does. In practice, estimating your lean body mass accurately requires a DEXA scan or similar test, and the common rules of thumb for grams per kilogram are already built around total body weight. Using your actual weight keeps the math simple and reliable enough for the vast majority of people.
The one exception is if you carry a very high amount of body fat. In that case, using total weight can overestimate protein needs. A reasonable workaround is to use your goal weight instead of your current weight when plugging numbers into the protein calculation.
Tracking Net Carbs vs. Total Carbs
If you follow a lower-carb approach, you may want to track net carbs rather than total carbs. Fiber passes through your body without being fully digested, so many people subtract fiber grams from total carbohydrates. Sugar alcohols (found in many protein bars and sugar-free products) are partially absorbed. UCSF’s diabetes education center recommends subtracting half the grams of sugar alcohols from the total carbohydrate count. So a bar with 29 grams of total carbs and 18 grams of sugar alcohols would count as 20 net carbs (29 minus 9).
For most people eating a standard diet, tracking total carbs is simpler and works fine. Net carbs become more relevant if you’re following a ketogenic diet or managing blood sugar.
Adjusting Over Time
The numbers you calculate on day one are a starting point, not a permanent prescription. Your body doesn’t read spreadsheets. Give any new macro target at least two to three weeks before deciding whether it’s working. Track your weight, energy levels, and workout performance over that window.
If you’re losing weight too fast (more than about 1% of your body weight per week), you’re likely losing muscle along with fat. Add 100 to 200 calories, primarily from carbs or protein. If the scale isn’t moving and fat loss is your goal, reduce by 200 calories, pulling mostly from carbs or fat while keeping protein steady. Protein is the macro you want to protect in almost every scenario, because it’s the one most directly tied to preserving muscle and keeping you full between meals.
As your weight changes, your calorie needs change too. Recalculating every 10 to 15 pounds of weight change, or every couple of months, keeps your targets relevant. The formula stays the same each time. You’re just updating the inputs.