Energy factors sourced to Atwater's original food-energy system
Plans this calculator uses
Pick a plan and this tool splits your calorie number by percentage, then converts each share into grams. The conversion itself relies on the Atwater system, the food-energy accounting method developed by chemist Wilbur Atwater at the USDA in the late 1800s and still the basis for the calorie counts on every nutrition label today: 4 calories per gram of carbohydrate or protein, 9 calories per gram of fat.
| Plan | Carb / Protein / Fat |
|---|---|
| Balanced | 50% / 25% / 25% |
| High protein | 40% / 40% / 20% |
| Low carb | 20% / 35% / 45% |
| Keto | 5% / 30% / 65% |
Grams, not percentages, are what you eat
Nobody weighs out "25 percent of a plate," so the calculator does the conversion for you. Take the balanced plan at 2,000 calories: protein gets 25 percent, or 500 calories, divided by 4 calories per gram for 125 grams. Carbs work the same way. Fat gets divided by 9 instead of 4, so its 25 percent share, also 500 calories, comes out to about 56 grams rather than 125, since each gram carries more than twice the energy.
Picking a plan without overthinking it
Balanced suits most people who just want a sane starting point. High protein tends to help with muscle retention during a cut or with muscle gain during a surplus; the bulking macro calculator on this site builds a full surplus and split around that goal. Low carb and keto are both lower-carbohydrate approaches, keto far more restrictive than low carb; the keto calculator on this site goes deeper into that specific split if it's the one you're after.
FAQs
Why does fat use 9 calories per gram instead of 4?
Fat is a more energy-dense molecule than carbohydrate or protein, so a gram of it releases more than double the energy when metabolized. That difference is exactly why a small amount of fat in a meal adds up in calories faster than the same weight of vegetables.
Do I need to hit these gram targets exactly every day?
No. A weekly average close to the target matters far more than nailing the number on any single day. Restaurant meals, travel and normal life will push a given day off target, and that's fine.
Can I build a custom split instead of the four presets?
Not on this page directly. This tool sticks to four common presets for simplicity; the keto calculator on this site lets you dial in exact carb, protein and fat percentages if you need something outside these four.
Which plan fits building muscle?
The high-protein preset is the usual pick, run against a calorie number at or slightly above maintenance. The TDEE calculator's mild-gain figure is a reasonable starting calorie total to plug in here.