How the grams are calculated
Each macronutrient gets a share of your daily calories, and the share is converted to grams using the standard Atwater energy factors: 4 calories per gram for protein, 4 for carbohydrate and 9 for fat. On 2,000 calories, 20% from protein is 400 calories, or 100 grams.
If you don't know your calorie target, the calculator estimates it with the Mifflin-St Jeor equation and your activity level, then adjusts for your goal: 500 calories less a day to lose about 1 lb a week, or 250 more to gain about half a pound. Weight-loss targets never go below 1,200 calories a day for women or 1,500 for men; the calorie calculator explains where those minimums come from.
The federal ranges these splits stay inside
The National Academies set Acceptable Macronutrient Distribution Ranges (AMDRs), which the Dietary Guidelines for Americans are designed to meet. For adults they are 10 to 35% of calories from protein, 45 to 65% from carbohydrate and 20 to 35% from fat.
All three presets sit inside those ranges. The lower-carb option stops at 45% carbohydrate, the bottom of the range; very low-carb and keto diets go well below it, which is outside what these guidelines cover.
The Dietary Guidelines for Americans, 2025–2030 also set a protein goal of 1.2 to 1.6 grams per kilogram of body weight per day. The calculator shows your protein in grams per kilogram so you can compare. A heavier person on a modest calorie target may need the higher-protein split to reach it.
Choosing a split
There is no single best split for weight loss. The 2013 AHA/ACC/TOS obesity guideline found that a variety of dietary approaches produce weight loss when they reduce calorie intake. So pick the split that fits how you like to eat and that you can keep up.
Quality matters within each number. The 2025–2030 guidelines favor a variety of protein foods, vegetables, fruits and whole grains, and limiting highly processed foods, refined carbohydrates and added sugars. They also say saturated fat should generally stay at or below 10% of daily calories.
The macro formulas
Protein (g) = calories × protein % ÷ 4Carbohydrate (g) = calories × carb % ÷ 4Fat (g) = calories × fat % ÷ 9- 4 and 9 are calories per gram (Atwater general factors)
- Percentages are written as decimals, so 20% = 0.20
Example
- Someone eating 2,000 calories a day who picks the balanced split (20% protein, 55% carbs, 25% fat) and weighs 160 lb (72.57 kg).
- Protein: 2,000 × 0.20 = 400 calories ÷ 4 = 100 g.
- Carbohydrate: 2,000 × 0.55 = 1,100 calories ÷ 4 = 275 g.
- Fat: 2,000 × 0.25 = 500 calories ÷ 9 = 56 g.
- Protein per kg: 100 ÷ 72.57 = 1.38 g/kg, inside the 1.2 to 1.6 g/kg goal.
Frequently asked questions
What are the recommended macro ratios?
For adults, the federal AMDRs are 10 to 35% of calories from protein, 45 to 65% from carbohydrate and 20 to 35% from fat. Any split inside those ranges is considered acceptable.
How much protein do I need a day?
The Dietary Guidelines for Americans, 2025–2030 set a goal of 1.2 to 1.6 grams per kilogram of body weight per day. At 160 lb (72.57 kg), that is about 87 to 116 grams.
How many grams of fat is 25% of 2,000 calories?
25% of 2,000 is 500 calories. Fat has 9 calories per gram, so that is about 56 grams.
Is a lower-carb split better for weight loss?
Not necessarily. The AHA/ACC/TOS obesity guideline found that a variety of diets lead to weight loss when they cut calories. A lower-carb split can help if it makes your calorie target easier to stick to.
What macros does this calculator give for a lightly active 160 lb woman?
For a 35-year-old woman at 5 ft 5 in eating to maintain (about 1,955 calories), the balanced split is about 98 g protein, 269 g carbohydrate and 54 g fat.
Sources
Last reviewed for 2026. How we calculate.