Calculating your macros for weight loss comes down to four steps: find your maintenance calories, subtract a deficit, set your protein and fat minimums, then fill the rest with carbohydrates. The whole process takes about ten minutes with a calculator, and the result is a personalized daily target for grams of protein, fat, and carbs that adds up to the right calorie total for losing fat.
Step 1: Find Your Maintenance Calories
Your maintenance calories are the number you’d eat to stay at your current weight. To find them, you first estimate your resting metabolic rate (the calories your body burns just keeping you alive), then multiply by an activity factor.
The most widely used formula is the Mifflin-St Jeor equation. You’ll need your weight in kilograms, height in centimeters, and age in years.
- For women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
- For men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 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 170 pounds (77.3 kg) and stands 5’6″ (167.6 cm) would calculate: (10 × 77.3) + (6.25 × 167.6) − (5 × 35) − 161 = roughly 1,467 calories at rest.
That resting number assumes you’re lying in bed all day. To account for real life, multiply it by one of these activity factors:
- Sedentary (desk job, no planned exercise): × 1.2
- Lightly active (light exercise 1–3 days per week): × 1.375
- Moderately active (moderate exercise 3–5 days per week): × 1.55
- Very active (hard exercise 6–7 days per week): × 1.725
If our example woman exercises three days a week, her maintenance calories would be about 1,467 × 1.55 = 2,274 calories per day. Most people overestimate their activity level, so if you’re unsure, pick the lower option. You can always adjust later.
Step 2: Set Your Calorie Deficit
To lose weight, you need to eat fewer calories than you burn. A deficit of about 500 calories per day produces roughly one pound of fat loss per week. That’s a solid, sustainable pace for most people. If you’d prefer a slower approach, a 250-calorie deficit still moves the scale while giving you more flexibility with meals.
Using the example above, 2,274 minus 500 gives a daily target of about 1,775 calories. This is the number you’ll now divide into protein, fat, and carbs. One important floor to keep in mind: going below roughly 1,200 calories per day increases the risk of nutrient gaps and constant hunger that makes overeating more likely.
Step 3: Set Your Protein Target
Protein is the macro you lock in first because it does the most work during weight loss. It preserves muscle mass while you’re in a deficit, keeps you feeling full longer, and burns slightly more calories during digestion than fat or carbs do.
The baseline recommendation is 0.8 grams per kilogram of body weight (about 0.36 grams per pound), but that’s a minimum for general health, not an optimal target for someone actively losing fat. A range of 0.7 to 1.0 grams per pound of body weight is a more practical target when your goal is preserving muscle during a calorie deficit. If you carry a significant amount of body fat, use your goal weight or lean body mass estimate instead of your current weight so the number doesn’t skew too high.
For our 170-pound woman aiming for a goal weight of around 145 pounds, setting protein at 0.8 grams per pound of goal weight gives about 116 grams of protein per day. Each gram of protein contains 4 calories, so that’s 464 calories allocated to protein.
Step 4: Set Your Fat Target
Fat is essential for hormone production, vitamin absorption, and cell function. Cutting it too low causes problems that go well beyond feeling hungry. A useful minimum is about 0.8 to 1.0 grams of fat per kilogram of body weight. For our example (77.3 kg), that’s roughly 62 to 77 grams of fat per day. Picking the middle of that range gives about 70 grams.
Each gram of fat contains 9 calories, more than double protein or carbs. So 70 grams of fat accounts for 630 calories. This is why even moderate amounts of fat take up a large share of your calorie budget, and why high-fat foods can quietly push you over your target if you’re not paying attention.
Step 5: Fill the Rest With Carbohydrates
Once protein and fat are set, the remaining calories go to carbohydrates. The math is simple subtraction and division.
Start with total calories (1,775) and subtract protein calories (464) and fat calories (630). That leaves 681 calories for carbs. Since carbohydrates contain 4 calories per gram, divide 681 by 4 to get about 170 grams of carbohydrates per day.
The final macro targets for this example:
- Protein: 116 g (464 calories)
- Fat: 70 g (630 calories)
- Carbs: 170 g (681 calories)
- Total: ~1,775 calories
Does the Exact Ratio Matter?
Less than you’d think. A large review published in The BMJ compared 14 popular diet programs, including low-carb and low-fat approaches, and found that at six months, low-carb and low-fat diets produced nearly identical weight loss (about 4.6 kg versus 4.4 kg). By 12 months, the differences between virtually all dietary patterns were negligible. The researchers concluded that people can choose the approach they prefer without worrying much about which ratio is “optimal.”
What this means in practice: if you love carbs, keep fat closer to the minimum and give yourself more carb grams. If you prefer fattier foods like avocado, cheese, and nuts, shift the balance the other way. The calorie deficit and adequate protein are doing the real work. The carb-to-fat split is mostly about what helps you stick with the plan.
Tracking Accurately
Your macro targets are only as good as your tracking. The biggest source of error isn’t the formula, it’s measuring food incorrectly.
A kitchen scale is far more reliable than measuring cups, especially for calorie-dense foods like peanut butter, oils, rice, and cheese. Weigh staples like oats, rice, and lentils dry (uncooked), since that’s how nutrition labels typically report them. For meats, pick either raw or cooked and stay consistent. If you weigh chicken breast raw before grilling, do that every time. Switching between raw and cooked weights without adjusting will throw your numbers off because meat loses roughly 25% of its weight during cooking.
For mixed dishes like stir-fries or casseroles, tracking each ingredient separately before cooking gives you the most accurate count. Pre-packaged items like rotisserie chicken or canned beans are already cooked, so use the cooked values on the label. Check whether the nutrition info says “as prepared” or “as served” to confirm.
When to Recalculate
Your macros aren’t permanent. As you lose weight, your body burns fewer calories at rest, which means the deficit that worked at 170 pounds won’t produce the same results at 155 pounds. A good rule of thumb is to recalculate after every 10 to 15 pounds of loss, or whenever your weight has stayed flat for two to three weeks despite consistent tracking.
Before recalculating, rule out the simpler explanations first. Portions tend to creep up over time, and activity levels sometimes drift downward without you noticing. Review your food log honestly. If everything checks out and the scale still isn’t moving, recalculate your maintenance calories using your new weight, reapply the 500-calorie deficit, and reset your macros from there. You may also add physical activity instead of cutting more food, since that preserves your calorie intake while restoring the deficit.
Keep your calories above that 1,200-calorie floor. If recalculating pushes your target below that, increasing exercise rather than further reducing food is the better path forward.