Figuring out your macros for weight loss comes down to three steps: estimate how many calories you need, subtract a deficit, then split those remaining calories among protein, carbs, and fat in grams. The whole process takes about ten minutes with a calculator, and once you understand the math, you can recalculate anytime your body or goals change.
Step 1: Estimate Your Daily Calories
Before you can set macros, you need a baseline: how many calories your body burns in a day. This starts with your basal metabolic rate (BMR), which is the energy your body uses just to stay alive at rest. The most widely used formula is the Harris-Benedict equation.
For men: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age in years)
For women: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) − (4.330 × age in years)
To convert pounds to kilograms, divide by 2.2. To convert inches to centimeters, multiply by 2.54. So a 170-pound, 5’8″ woman who is 35 years old would calculate: 447.593 + (9.247 × 77.3) + (3.098 × 172.7) − (4.330 × 35) = roughly 1,547 calories at rest.
Your BMR only covers resting energy. To account for daily movement and exercise, multiply it by an activity factor:
- Sedentary (desk job, little 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
The result is your total daily energy expenditure, or maintenance calories. Using the example above, if that woman exercises three days a week, her maintenance level would be roughly 1,547 × 1.375 = about 2,127 calories per day.
Step 2: Set Your Calorie Deficit
Cutting about 500 calories per day from your maintenance level typically produces a loss of roughly half a pound to one pound per week. That rate varies depending on your starting weight, sex, and activity level, but it’s a reliable starting point for most people. For the example above, that means a daily target of about 1,627 calories.
Going much below a 500-calorie deficit can work in the short term, but it gets harder to hit adequate protein and micronutrient levels the lower you go. If your calculated target drops below about 1,200 calories (for women) or 1,500 (for men), you’re better off increasing activity rather than cutting food further.
Step 3: Choose Your Macro Split
The federal Dietary Guidelines list the Acceptable Macronutrient Distribution Ranges for adults as 10–35% of calories from protein, 45–65% from carbohydrates, and 20–35% from fat. Those ranges are wide on purpose. For weight loss specifically, shifting toward the higher end for protein and adjusting carbs and fat to preference tends to produce better results.
A common starting split for weight loss is 30% protein, 40% carbohydrates, and 30% fat. This isn’t the only option, but it prioritizes protein enough to protect muscle mass while keeping carbs high enough to fuel workouts and fat high enough to support hormones and satiety. Some people prefer lower carb and higher fat, or vice versa. The protein target matters most; carbs and fat can flex around your preferences and how you feel.
Why Protein Gets Priority
When you’re in a calorie deficit, your body doesn’t just burn fat. It can also break down muscle for energy, especially if protein intake is too low. Research from UCLA Health suggests that someone aiming to lose weight may benefit from consuming around 2.3 grams of protein per kilogram of body weight to preserve muscle during the process. For a 170-pound person, that works out to roughly 178 grams of protein per day.
That number is higher than the standard recommendation for the general population, which sits around 0.8 grams per kilogram. If 2.3 grams per kilogram feels like a lot, even getting to 1.6 grams per kilogram is a meaningful improvement over what most people eat. Protein also has a stronger effect on fullness than carbs or fat, which makes sticking to a deficit easier.
Step 4: Convert Percentages to Grams
This is where the actual tracking numbers come from. You need three facts: protein and carbohydrates each provide 4 calories per gram, and fat provides 9 calories per gram. With those conversion rates, the math is straightforward.
Using a 1,600-calorie target with a 30/40/30 split:
- Protein (30%): 1,600 × 0.30 = 480 calories ÷ 4 = 120 grams
- Carbohydrates (40%): 1,600 × 0.40 = 640 calories ÷ 4 = 160 grams
- Fat (30%): 1,600 × 0.30 = 480 calories ÷ 9 = 53 grams
Those are your daily targets. You can round to the nearest 5 grams to keep things simple. Nobody needs to hit these numbers exactly every day. Staying within 5 to 10 grams of each target consistently is more than precise enough.
The Protein-First Alternative
Some people find it easier to skip percentages entirely and set protein in grams first, then divide the remaining calories between carbs and fat. For example, if you decide on 150 grams of protein (600 calories), you subtract that from your 1,600-calorie budget, leaving 1,000 calories to split between carbs and fat however you like. If you go 60/40 on the remaining calories, that’s 150 grams of carbs and about 44 grams of fat. This approach ensures protein doesn’t get squeezed out by the other macros.
Putting It Into Practice
Knowing your macro targets is one thing. Actually hitting them requires some form of tracking, at least initially. Most people use an app where you log food and it tallies your macros automatically. After a few weeks, you’ll develop an intuitive sense of what a 30-gram protein meal looks like or how much rice adds up to 40 grams of carbs. At that point, strict logging becomes optional.
A few practical tips that make the first weeks easier: build each meal around a protein source first, then add carbs and fat around it. Protein is the hardest macro to hit for most people, so front-loading it prevents the end-of-day scramble. Batch-cooking proteins like chicken, eggs, or beans at the start of the week removes a lot of daily decision-making. And if you drink alcohol, note that it contributes 7 calories per gram but doesn’t fit neatly into any macro category, so those calories simply get subtracted from your overall budget.
When to Recalculate Your Macros
Your macro targets aren’t permanent. As you lose weight, your body burns fewer calories at rest because there’s less of you to maintain. A good rule of thumb is to recalculate after every 10 to 15 pounds lost, or whenever your weight stops changing for two to three consecutive weeks despite consistent adherence to your targets.
When you hit a plateau, the fix is usually small. Dropping your daily target by 100 to 200 calories, or adding one or two additional exercise sessions per week, is typically enough to restart progress. Resist the urge to slash calories dramatically. Large sudden cuts tend to increase hunger, reduce energy, and make the plan harder to stick with, which is the only thing that actually matters long-term.
If your activity level changes significantly (you start a new job, pick up a sport, or stop going to the gym), recalculate from the activity multiplier step. The macro percentages can stay the same. It’s the calorie total that shifts.