Calculating your macros is a three-step process: estimate how many calories your body burns each day, adjust that number for your goal (lose fat, build muscle, or maintain weight), then divide those calories among protein, carbohydrates, and fat. The whole calculation takes about five minutes with a calculator, and once you understand the logic, you can recalculate whenever your weight, activity, or goals change.
Step 1: Estimate Your Basal Metabolic Rate
Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest, just keeping your organs running, your lungs breathing, and your cells alive. It accounts for the largest share of your daily calorie burn, typically 60 to 70 percent.
The most widely used formula is the Mifflin-St Jeor equation. You need three numbers: your weight in kilograms, your height in centimeters, and your age in years. To convert pounds to kilograms, divide by 2.2. To convert inches to centimeters, multiply by 2.54.
- Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age) + 5
- Women: (10 × weight in kg) – (6.25 × height in cm) – (5 × age) – 161
For example, a 35-year-old woman who weighs 70 kg (154 lbs) and stands 165 cm (5’5″) tall would calculate: (10 × 70) + (6.25 × 165) – (5 × 35) – 161 = 700 + 1,031 – 175 – 161 = 1,395 calories. That’s her BMR, the bare minimum her body needs if she stayed in bed all day.
Step 2: Factor In Your Activity Level
You don’t stay in bed all day, so the next step is multiplying your BMR by an activity factor to get your total daily energy expenditure (TDEE). This is the number of calories you actually burn in a normal day, including movement, exercise, and even digesting food.
- Sedentary (desk job, little or no exercise): BMR × 1.2
- Lightly active (light exercise 1 to 3 days per week): BMR × 1.375
- Moderately active (moderate exercise 3 to 5 days per week): BMR × 1.55
- Very active (hard exercise 6 to 7 days per week): BMR × 1.725
Using the same example, if that woman exercises moderately three to five days a week, her TDEE would be 1,395 × 1.55 = roughly 2,162 calories per day. This is her maintenance number, the calorie intake where she’d neither gain nor lose weight over time.
Be honest with yourself when picking a category. Most people overestimate how active they are. If you work out three times a week but sit at a desk the rest of the time, “lightly active” is usually more accurate than “moderately active.”
Step 3: Adjust Calories for Your Goal
Your TDEE is the starting point. What you do with it depends on whether you want to lose fat, gain muscle, or stay where you are.
For fat loss, subtract roughly 500 calories per day from your TDEE. This creates a deficit that typically produces about half a pound to one pound of weight loss per week. So if your TDEE is 2,162, you’d aim for around 1,662 calories daily. Cutting more aggressively can work short-term but tends to increase muscle loss and make the diet harder to sustain.
For muscle gain, add a modest surplus. Research comparing a 5% surplus to a 15% surplus found that the larger surplus led to more fat gain without meaningfully more muscle growth or strength. A 5 to 10% increase is the sweet spot. On a 2,162-calorie TDEE, that’s roughly 108 to 216 extra calories, putting your target at about 2,270 to 2,378 calories. A good check is watching the scale over two weeks: gaining 0.25 to 0.5% of your body weight per week means you’re in the right range.
For maintenance, eat at your TDEE. This is useful during periods when you want to build healthy habits without pushing toward a specific body composition change.
Step 4: Set Your Protein Target
Protein is the macro most worth getting right because it drives muscle repair, keeps you feeling full, and has the highest thermic effect (your body burns more calories digesting protein than carbs or fat). The general recommendation for adults is 0.8 grams per kilogram of body weight, but that’s a minimum for basic health, not an optimal target for someone exercising regularly or trying to change their body composition.
For most active people aiming to lose fat or gain muscle, a range of 1.6 to 2.2 grams per kilogram of body weight works well. On the higher end if you’re in a caloric deficit, because extra protein helps preserve muscle when calories are low. For our example woman at 70 kg, that’s 112 to 154 grams of protein per day.
Each gram of protein contains 4 calories. So 130 grams of protein (a middle-ground target for her) equals 520 calories from protein.
Step 5: Set Your Fat Target
Dietary fat supports hormone production, helps your body absorb certain vitamins, and contributes to feeling satisfied after meals. The Dietary Guidelines for Americans recommend that 20 to 35% of your total calories come from fat.
A starting point of 25 to 30% works for most people. If our example woman is eating 1,662 calories for fat loss, 25% of that is about 415 calories from fat. Each gram of fat contains 9 calories, so that’s roughly 46 grams of fat per day. Going below 20% of total calories from fat for extended periods can interfere with hormonal balance, so it’s generally not worth pushing that low.
Step 6: Fill the Rest With Carbohydrates
Carbohydrates are whatever’s left after protein and fat are accounted for. They’re your body’s preferred fuel source for exercise and brain function, and there’s no need to minimize them unless you have a specific medical reason to do so. The general range for adults is 45 to 65% of total calories.
Here’s the math for our example on a 1,662-calorie fat loss plan:
- Protein: 130 g × 4 calories = 520 calories
- Fat: 46 g × 9 calories = 414 calories
- Remaining for carbs: 1,662 – 520 – 414 = 728 calories
- Carbs in grams: 728 ÷ 4 = 182 grams
Her final macro targets would be 130g protein, 46g fat, and 182g carbs. That’s it. Those three numbers are “your macros.”
Why Precision Has Limits
These calculations give you a solid starting point, but they’re estimates, not prescriptions. The Mifflin-St Jeor equation predicts BMR for populations, and individual metabolism can vary based on genetics, muscle mass, sleep, stress, and other factors the equation doesn’t capture.
Food labels themselves carry built-in imprecision. Under FDA regulations, the actual calorie content of a food can be up to 20% higher than what’s listed on the label and still be considered compliant. Protein and carbohydrate counts need to be within 80% of the declared value. So if a label says 200 calories, the food could contain up to 240.
This doesn’t mean tracking is pointless. It means you should treat your macro targets as a compass, not a GPS coordinate. Hit your numbers within 5 to 10 grams on most days and you’re doing well. The real adjustment happens over time: track your weight and how you look and feel over two to three weeks, then nudge your calories up or down by 100 to 200 based on what’s actually happening. If you’re losing weight faster than a pound a week, you can afford to eat a bit more. If the scale isn’t moving, trim calories slightly or reassess your activity multiplier.
Adjusting Your Ratios for Different Goals
The Acceptable Macronutrient Distribution Ranges (10 to 35% protein, 45 to 65% carbs, 20 to 35% fat) are broad on purpose. Where you land within them depends on your priorities.
If you’re focused on endurance training, you’ll generally want carbs on the higher end to fuel long sessions. If you’re strength training and trying to build or preserve muscle, protein sits at the higher end and you can be more flexible with the carb-to-fat ratio. If you find that higher-fat meals keep you more satisfied, you can shift fat toward 30 to 35% and let carbs drop toward 40 to 45%, as long as protein stays consistent.
The one macro that should stay relatively fixed regardless of your approach is protein. It’s the most important for body composition, and most people undereat it. Carbs and fat are more interchangeable. Some people feel better on higher carbs, others on higher fat. Experiment within the ranges and pay attention to your energy, hunger, and performance in the gym. The best macro split is the one you can actually stick to.