Figuring out your macros for weight loss comes down to three steps: estimate how many calories you burn daily, subtract enough to create a deficit, then divide those remaining calories among protein, carbs, and fat. The whole process takes about ten minutes with a calculator, and you can fine-tune it as you go.
Step 1: Estimate Your Daily Calorie Burn
Your body burns a baseline number of calories just keeping you alive: breathing, circulating blood, maintaining body temperature. This is your basal metabolic rate, or BMR. The most widely used formula for estimating it is the Mifflin-St Jeor equation, which uses your weight in kilograms, height in centimeters, and age in years.
For men: (10 × weight) + (6.25 × height) – (5 × age) + 5
For women: (10 × weight) + (6.25 × height) – (5 × age) – 161
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 1,460 calories per day at rest.
But you don’t lie in bed all day, so you need to account for movement. Multiply your BMR by an activity factor:
- Sedentary (desk job, no planned 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 a physical job): BMR × 1.9
That same woman with a desk job who walks three times a week would multiply 1,460 by 1.375, giving her a total daily energy expenditure (TDEE) of about 2,008 calories. This is her maintenance number, the amount she’d eat to stay the same weight. Most people overestimate their activity level, so if you’re on the fence between two categories, pick the lower one.
Step 2: Set Your Calorie Deficit
To lose one pound per week, you need a daily deficit of about 500 calories. For two pounds per week, that’s a 1,000-calorie deficit. A rate of one to two pounds per week is generally sustainable and less likely to trigger the intense hunger and fatigue that come with aggressive dieting.
Using the example above, a 500-calorie deficit from a 2,008-calorie TDEE gives a target of roughly 1,500 calories per day. One important floor to keep in mind: women generally shouldn’t go below 1,200 calories per day, and men shouldn’t go below 1,500, because eating less than that makes it very difficult to get the nutrients your body needs.
Step 3: Divide Calories Into Macros
Each gram of protein and carbohydrate contains 4 calories. Each gram of fat contains 9. These conversion numbers are how you’ll translate your calorie target into grams of each macronutrient. Federal dietary guidelines set broad ranges for healthy adults: 10-35% of calories from protein, 45-65% from carbohydrates, and 20-35% from fat. For weight loss, you’ll want to push toward the higher end of protein and adjust the other two to fit.
Start With Protein
Protein is the most important macro to get right when you’re in a deficit. It protects your muscle mass, keeps you feeling full longer, and burns more calories during digestion than carbs or fat do. A good starting point is 1.2 grams of protein per kilogram of body weight per day, which research has shown is effective for preserving muscle during calorie restriction. If you’re doing regular strength training, you may benefit from going up to 1.6 grams per kilogram or even higher.
For our 170-pound (77.3 kg) example, 1.2 grams per kilogram equals about 93 grams of protein per day. At 4 calories per gram, that’s 372 calories dedicated to protein, or roughly 25% of a 1,500-calorie budget.
Then Set Fat
Fat is essential for hormone production, nutrient absorption, and brain function. A common target for weight loss is 25-30% of total calories. At 1,500 calories, 25% gives you 375 calories from fat. Divide by 9 calories per gram, and you get about 42 grams of fat per day. Going below 20% of calories from fat for extended periods can interfere with hormone balance, so treat that as a practical floor.
Fill the Rest With Carbs
Whatever calories remain after protein and fat go to carbohydrates. In this example: 1,500 total – 372 (protein) – 375 (fat) = 753 calories from carbs. Divide by 4 calories per gram, and you land at about 188 grams of carbohydrates. Your brain alone needs roughly 130 grams of carbs per day to function well, so drastically cutting carbs below that level can leave you foggy and irritable. For people who are physically active, carbs also fuel your workouts and support recovery.
A Complete Example
Putting it all together for a 35-year-old, lightly active woman at 170 pounds and 5’6″:
- TDEE: ~2,008 calories
- Deficit target: ~1,500 calories (about 1 lb/week loss)
- Protein: 93 g (372 calories)
- Fat: 42 g (375 calories)
- Carbs: 188 g (753 calories)
These numbers are a starting point, not a permanent prescription. Your body will respond over the first two to three weeks, and then you’ll have real data to adjust from.
Why Tracking Isn’t Perfectly Precise
Even careful tracking has built-in inaccuracy. FDA labeling rules allow calories to be rounded to the nearest 5-calorie increment (or 10 calories above 50), fat to the nearest half gram below 5 grams, and protein and carbs to the nearest gram. A food with 0.4 grams of fat per serving can legally list zero. If you eat several of those servings across a day, those hidden fractions add up. This doesn’t mean tracking is useless. It means you should treat your macro targets as a range rather than a bullseye. Hitting within 5-10 grams of your protein target and within 100 calories of your total is plenty accurate for consistent results.
When to Recalculate Your Macros
As you lose weight, your body burns fewer calories simply because there’s less of you to maintain. A good rule of thumb is to recalculate after every 10-15 pounds lost, or whenever your weight has stalled for more than two weeks despite consistent tracking. Plugging your new weight into the same formulas will give you an updated TDEE and a fresh set of macros.
Plateaus can also happen because of metabolic adaptation, where your body temporarily becomes more efficient with energy during prolonged dieting. Research from the University of Alabama at Birmingham found that this adaptation significantly decreases or even disappears after just a couple of weeks of eating at maintenance. So if your weight stalls, spending two weeks eating at your current maintenance calories (not your original ones) can reset things before you resume your deficit. This isn’t failure. It’s a useful tool.
Choosing the Right Ratio for You
The 25/25/50 split (protein/fat/carbs by calories) used in the example above is a solid default, but there’s no single correct ratio. What matters most is hitting your protein minimum and staying within your calorie target. After that, the balance between carbs and fat is largely personal preference.
If you do better with more fat and fewer carbs, you could shift to something like 30% protein, 35% fat, and 35% carbs. If you’re a runner or do other endurance exercise, you might want closer to 50-55% of calories from carbs to keep your energy up. The best macro split is the one you can actually stick to for months, because consistency matters far more than optimization. If you find yourself constantly hungry, try increasing protein or fat slightly and reducing carbs by the same number of calories. If your workouts feel flat, add carbs back and trim fat. Small shifts of 5-10% at a time let you dial in what works without overhauling your entire diet.