Calculating keto macros starts with one core ratio: roughly 70–80% of your daily calories from fat, 10–20% from protein, and 5–10% from carbohydrates. On a 2,000-calorie diet, that works out to about 165 grams of fat, 75 grams of protein, and 40 grams of carbs. But those are averages. Your actual numbers depend on your body size, activity level, and goals.
Step 1: Find Your Daily Calorie Target
Before you can split calories into fat, protein, and carbs, you need to know how many calories your body burns in a day. The most widely used method is the Mifflin-St Jeor equation, which estimates your basal metabolic rate (the calories your body needs just to keep you alive at rest).
For men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
For women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 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 160 pounds (72.7 kg) and stands 5’6″ (167.6 cm) would calculate: (10 × 72.7) + (6.25 × 167.6) − (5 × 35) − 161 = roughly 1,413 calories at rest.
That resting number then gets multiplied by an activity factor to reflect how much you actually move during the day:
- Sedentary (desk job, little exercise): multiply by 1.2
- Lightly active (light exercise 1–3 days per week): multiply by 1.375
- Moderately active (moderate exercise 3–5 days per week): multiply by 1.55
- Very active (hard exercise 6–7 days per week): multiply by 1.725
If that same woman exercises moderately, her total daily energy expenditure would be about 1,413 × 1.55 = 2,190 calories. To lose weight, subtract 10–20% from that number. To maintain, use it as is.
Step 2: Set Your Carbs First
Carbs are the tightest constraint on keto, so lock this number in before anything else. Most people stay in ketosis eating 20 to 50 grams of net carbs per day. If you’re just starting out, 20 grams is a reliable floor that virtually guarantees ketosis. As you adapt, you can experiment with slightly higher amounts and see how your body responds.
Net carbs are what matter here, not total carbs. The difference is fiber and certain sugar alcohols, which your body doesn’t absorb the same way. The basic formula: total carbohydrates minus fiber equals net carbs. If a food contains sugar alcohols (like maltitol, xylitol, or sorbitol), subtract half their grams from total carbs rather than the full amount, since your body still partially absorbs them.
For example, a protein bar with 22 grams of total carbs, 4 grams of fiber, and 10 grams of sugar alcohols would have: 22 − 4 − 5 = 13 grams of net carbs. Erythritol is the one exception most people subtract fully, since virtually none of it gets absorbed.
Step 3: Calculate Your Protein
Protein is the next priority. You need enough to preserve muscle mass, but not so much that it interferes with ketosis. Your body can convert amino acids from protein into glucose, so the ketogenic diet keeps protein moderate compared to other low-carb approaches.
A practical starting point is 0.7 to 1.0 grams of protein per pound of lean body mass. Lean body mass is your total weight minus your body fat. If you weigh 180 pounds and estimate you’re at 25% body fat, your lean mass is about 135 pounds, which means a protein target of roughly 95 to 135 grams per day. If you don’t know your body fat percentage, you can estimate using online calculators or simply aim for 0.6 to 0.8 grams per pound of total body weight as a rough guideline.
People who are very active or doing resistance training should lean toward the higher end of that range. People who are more sedentary can stay at the lower end. Each gram of protein contains 4 calories, so 100 grams of protein equals 400 calories from your daily total.
Step 4: Fill the Rest With Fat
Once carbs and protein are set, the remaining calories all come from fat. This is straightforward math. Each gram of fat contains 9 calories, each gram of carbs or protein contains 4.
Here’s a worked example using a 1,800-calorie target with 25 grams of net carbs and 110 grams of protein:
- Carbs: 25 g × 4 calories = 100 calories
- Protein: 110 g × 4 calories = 440 calories
- Remaining for fat: 1,800 − 100 − 440 = 1,260 calories
- Fat in grams: 1,260 ÷ 9 = 140 grams
That puts this person at roughly 70% fat, 24% protein, and 6% carbs. The exact percentages will shift depending on your individual numbers, and that’s fine. The percentages are guidelines, not rigid rules. What matters most is keeping net carbs low enough for ketosis, getting adequate protein, and letting fat fill the gap.
Why the Order Matters
A common mistake is starting with the fat percentage and working backward. This often leads to either too little protein (which costs you muscle over time) or too many carbs (which kicks you out of ketosis). By setting carbs first as a hard limit, protein second based on your body composition, and fat last as the flexible variable, you protect both muscle mass and ketosis while still hitting your calorie target.
Fat is also the lever you adjust if your goals change. Trying to lose weight faster? Reduce fat grams slightly. Feeling low on energy or struggling with hunger? Add fat back. Your carb and protein targets generally stay consistent.
Tracking Net Carbs in Practice
The math above gives you daily targets, but hitting them requires knowing what’s in your food. During the first few weeks, most people benefit from weighing portions and logging meals in an app. This builds intuition quickly. After a month or so, many people can estimate portions accurately enough to track loosely.
Pay close attention to hidden carbs. Sauces, dressings, and condiments frequently contain added sugars. A single tablespoon of barbecue sauce can have 6 or 7 grams of carbs. Vegetables vary widely too. Leafy greens are extremely low in net carbs, while starchier options like carrots or onions add up faster than you might expect.
Electrolytes: The Hidden Variable
Macros aren’t the only numbers to track on keto. When you cut carbs dramatically, your kidneys flush more sodium and water, which pulls other minerals along with it. This is the primary cause of “keto flu,” the headaches, fatigue, and muscle cramps that hit in the first week or two.
Daily electrolyte targets to aim for on keto are higher than what most people expect:
- Sodium: 4 to 6 grams (significantly more than the standard dietary guideline)
- Potassium: 3.5 to 5 grams
- Magnesium: 400 to 600 milligrams
- Calcium: about 1 gram
Salting your food generously, eating avocados and leafy greens, and supplementing magnesium are the simplest ways to stay on top of these numbers. If you’re experiencing cramps, brain fog, or fatigue in the first couple weeks, inadequate electrolytes are almost always the cause before anything else.
Adjusting Over Time
Your starting macros are a best guess, not a permanent prescription. After two to three weeks, evaluate how things are going. If you’re losing weight too quickly (more than 2 pounds per week after the initial water weight drop), add some fat back. If weight loss has stalled, double-check that hidden carbs haven’t crept in, and consider reducing your fat intake by 10–15%.
As your weight changes, your calorie needs change too. Recalculating every 10 to 15 pounds of weight loss keeps your macros aligned with your current body. Your protein target also shifts as lean mass changes, though more gradually. Revisiting the full calculation every couple of months is a reasonable rhythm for most people.