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 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 split calories into macros, you need a reasonable calorie target. That starts with your basal metabolic rate (BMR), the energy your body burns at complete rest just to keep you alive. The most widely used formula is the Mifflin-St Jeor equation:
- Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
- Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
To convert pounds to kilograms, divide by 2.2. To convert inches to centimeters, multiply by 2.54. So a 35-year-old woman who weighs 155 pounds (70.5 kg) and stands 5’6″ (167.6 cm) would get: (10 × 70.5) + (6.25 × 167.6) − (5 × 35) − 161 = roughly 1,392 calories at rest.
But you don’t lie in bed all day. To get your total daily energy expenditure (TDEE), multiply your BMR by an activity factor:
- Sedentary (desk job, no exercise): BMR × 1.2
- Lightly active (exercise 1–3 days per week): BMR × 1.375
- Moderately active (exercise 3–5 days per week): BMR × 1.55
- Very active (hard exercise 6–7 days per week): BMR × 1.725
- Extra active (intense training plus physical job): BMR × 1.9
Using the example above, if that woman exercises three times a week, her TDEE would be about 1,392 × 1.375 = roughly 1,914 calories per day. That number is your maintenance estimate, the starting point everything else builds on. Most people fall somewhere between the sedentary and moderately active categories. If you’re unsure, pick the lower option. You can always adjust upward later.
Step 2: Adjust Calories for Your Goal
Your TDEE tells you what it takes to maintain your current weight. From there, you shift the number based on what you’re after.
For fat loss, subtract 300 to 500 calories from your TDEE. A good target rate of loss is about 0.5 to 1.0% of your total body weight per week. Going much faster than that tends to sacrifice muscle along with fat. For muscle gain, add 200 to 400 calories above your TDEE. If you want to stay where you are and just improve your food quality, use your TDEE as is.
Step 3: Choose Your Macro Split
Now you divide those calories among the three macronutrients. Each one provides a different amount of energy per gram: protein has 4 calories per gram, carbohydrates have 4 calories per gram, and fat has 9 calories per gram. (Alcohol, for reference, sits at 7 calories per gram, which is worth knowing if drinks are part of your routine.)
The U.S. Dietary Guidelines recommend broad ranges for adults 14 and older: 45–65% of calories from carbs, 10–35% from protein, and 20–35% from fat. Those ranges are designed for general health, but most people searching for their macros want something more targeted. Here are common starting splits based on specific goals:
Maintenance or General Health
A balanced split of roughly 40–50% carbs, 25–35% protein, and 20–30% fat works well for people who want to eat well without chasing a particular body composition goal.
Fat Loss While Preserving Muscle
Bump protein to 30–35% of your (reduced) calories, keep carbs at 30–40%, and fat at 25–30%. The higher protein ratio helps protect lean mass while you’re in a calorie deficit. For someone eating 1,500 calories on a fat loss plan at 35% protein, that’s 525 calories from protein, or about 131 grams per day.
Muscle Gain
With your calories above maintenance, aim for 40–55% carbs, 25–35% protein, and 20–30% fat. The extra carbs fuel hard training sessions and support recovery. Protein stays high to supply the building blocks for new tissue.
Ketogenic Approach
Keto flips the standard ratio on its head: 70–80% fat, 10–20% protein, and just 5–10% carbs. In practice, that means fewer than 50 grams of carbohydrates a day, sometimes as low as 20 grams. That’s less than what’s in a single plain bagel. This split forces the body to rely on fat for fuel, which is why it requires such a dramatic reduction in carbs.
Converting Percentages to Grams
Once you’ve picked your calorie target and your percentage split, the math is simple. Multiply your total calories by each macro’s percentage, then divide by the calories per gram for that nutrient.
Say your target is 2,000 calories with a 40% carb, 30% protein, 30% fat split:
- Carbs: 2,000 × 0.40 = 800 calories ÷ 4 = 200 grams
- Protein: 2,000 × 0.30 = 600 calories ÷ 4 = 150 grams
- Fat: 2,000 × 0.30 = 600 calories ÷ 9 = 67 grams
Those gram targets are what you actually track day to day, whether you use a food tracking app or a notebook.
Setting Protein as a Fixed Number
Many people prefer to set protein in grams per unit of body weight first, then fill in the rest with carbs and fat. This approach makes sense because protein needs are more tightly linked to your body size and activity level than to your calorie intake.
The baseline recommendation for sedentary adults is 0.8 grams per kilogram of body weight, but that’s designed to prevent deficiency, not optimize body composition. People who lift weights regularly or train for endurance sports need 1.2 to 1.7 grams per kilogram. And if you’re over 40, even baseline needs creep up to about 1.0 to 1.2 grams per kilogram to counteract the natural muscle loss that begins around that age.
For a 180-pound (82 kg) person who lifts weights three times a week, the protein target would land between 98 and 139 grams per day. Pick a number in that range, multiply it by 4 to get the calories from protein, subtract that from your total calorie budget, then divide the remaining calories between carbs and fat in whatever ratio suits your preferences and energy needs.
A Note on Fiber Within Your Carbs
Not all carbohydrate grams are created equal. The general guideline is 14 grams of fiber per 1,000 calories you eat. For most adults that works out to roughly 25–34 grams per day, with men needing a bit more than women. Fiber is counted within your carbohydrate total, but because your body can’t fully digest it, some trackers subtract fiber from total carbs to show “net carbs.” If you’re following a keto plan where every gram of carbohydrate matters, net carbs become especially relevant. For most other approaches, just aim to get your fiber from whole grains, vegetables, and fruit without overthinking the net carb distinction.
When to Recalculate Your Macros
Your macros aren’t set permanently. As your weight changes, your BMR changes with it, which means the calorie target that created a deficit three months ago might now be your new maintenance level. At the same time, as your fitness improves, you burn fewer calories doing the same workout you did when you started. Both of these shifts can stall progress.
A practical approach is to weigh yourself at least three times a week (at the same time, under the same conditions) and watch the weekly average rather than any single reading. If your average weight hasn’t budged in two to three weeks and your goal is still fat loss, it’s time to recalculate. Drop your calorie target by another 100 to 200 calories, redistribute your macros accordingly, or add more activity. An appropriate rate of weight loss is about 0.5 to 1.0% of your body weight per week. If you’re losing faster than that, you may be cutting too aggressively.
For muscle gain, the reverse applies. If you’re not gaining weight over a two to three week stretch despite consistent training, increase your calories by 100 to 200 and add those extra calories to carbs or a mix of carbs and fat to fuel harder workouts.