Macros in plain English
Macronutrients — protein, carbohydrate, and fat — are the three things you actually eat from a calorie perspective. (Alcohol is a fourth, nutritionally unhelpful one.) The calories you eat come almost entirely from these three: protein and carbs deliver 4 calories per gram, fat delivers 9. Everything in nutrition gets complicated fast, but the split between these three is where most of the body-composition leverage lives.
Why the split matters
If you're in a 500-calorie deficit and you get to 400 calories of that deficit entirely from protein vs. from soda, the scale will move the same either way — but you will look very different after three months. Protein preserves muscle during weight loss. Carbs and fat, in a deficit, do not. Once calories are fixed, the protein floor is the single most important macro choice you make.
How this calculator picks your macros
You provide daily calories (from the TDEE calculator) and a goal. The split defaults by goal:
- Cutting: 40/30/30 (protein/carbs/fat). High protein to protect muscle in a deficit.
- Maintaining: 30/40/30. Balanced and sustainable.
- Bulking: 30/50/20. Carbs drive training intensity and recovery.
- Keto: 25/5/70. Enough protein to preserve muscle, carbs suppressed to drive nutritional ketosis.
- High-carb / endurance: 20/60/20. Designed for runners, cyclists, and athletes training 10+ hours a week.
On top of those splits, we apply a protein floor based on bodyweight — at least 1.0 g per pound during a cut, 0.9 g per pound during a bulk, and 0.7 g per pound for maintenance. If the percentage split would drop protein below that floor, the calculator raises protein and recalculates.
Protein — the one macro nobody hits
Surveys consistently show most adults eat 0.4–0.6 g of protein per pound of bodyweight. Research on muscle retention and satiety suggests 0.7–1.0 g per pound is the useful range for most active people. That means a 170 lb person should target 120–170 g of protein daily, not the 70 g the average plate delivers. The full protein case lives in the dedicated protein intake calculator.
Practical ways to hit 30–40 g protein per meal: a 6 oz chicken breast, a can of tuna plus Greek yogurt, two eggs plus 4 oz of turkey, a scoop of whey in a smoothie, 8 oz of cottage cheese, or a 1 cup portion of lean ground beef.
Carbs — training fuel, not the enemy
Carbs are the primary fuel for any training session above walking intensity. Low-carb diets work for weight loss when total calories are controlled; they do not work as well when you're trying to lift heavy or run hard. If your training is serious and your body composition is already reasonable, the 50% carb bulk split is there for a reason.
On a cut, carbs are the first macro to squeeze (after keeping protein high), because fat has essential fatty acids you need minimum amounts of, and protein has the muscle-sparing effect. 30% carbs during a cut still leaves ~180 g of carbs on a 2,400-kcal day — plenty to fuel 3–4 lifting sessions a week.
Fat — hormones and satiety
Your body needs roughly 0.3 g of fat per pound of bodyweight minimum for healthy hormone production. Below that, testosterone and other sex hormones drop. On this calculator, the fat floor lives inside the default splits — even the bulk split (20% fat) clears the floor for most people.
On keto, fat becomes the primary fuel source and calorie buffer. The 70% fat split is intentionally high, pushing carbs well under the 50 g/day threshold most people need to enter ketosis.
Keto, specifically
Keto works by restricting carbs hard enough that your liver converts fat into ketones, which the body (and brain) can use as fuel. The diet is genuinely effective for weight loss, epilepsy management, and insulin sensitivity in some people. It's also hard to sustain, incompatible with most carbohydrate-dependent sports, and socially annoying. The protein cap matters: above ~1 g per pound, gluconeogenesis can partially exit ketosis. That's why the keto split caps protein at 25% and fat fills the rest.
Tracking: don't skip the first month
The hardest part of any macro plan is learning what 40 g of protein actually looks like on a plate. Log your food for 30 days using any app (Cronometer, MyFitnessPal, MacroFactor all work). After a month you'll have intuitive feel for portion sizes and can ease up on strict tracking. People who skip the learning phase almost always under-count protein and over-count fat.
When to recalculate
- Your weight has changed by 5+ lb.
- You switched goals (cutting → maintain → bulking).
- Training volume changed meaningfully — a new program, a new sport, or an injury layoff.
- You're hitting the macros but the scale isn't moving the way TDEE predicts. Recalculate TDEE first, then macros.
FAQ
Do I need to hit macros exactly?
No. Protein should be hit within ±10 g. Carbs and fat can flex ±20 g as long as total calories are within ±100 of target. Daily perfection isn't required; weekly consistency is.
What about fiber, sugar, sodium?
Those are "micro-macros." Aim for 25+ g fiber daily, keep added sugar under ~50 g, and sodium under ~2,300 mg unless you're a hard-training athlete. None of these are counted in the basic macro split, but they all matter for health and performance.
What about alcohol?
Alcohol is 7 kcal/gram, doesn't slot into any of the three macros cleanly, and interferes with muscle protein synthesis. If you drink, count the calories toward your daily total (typically displacing carbs or fat, not protein) and accept the recovery cost.
Is IIFYM (If It Fits Your Macros) legit?
Macro-based eating works. Pretending that 2,400 kcal of Pop-Tarts is the same as 2,400 kcal of whole foods, however, doesn't — food quality drives micronutrient intake, satiety, and gut health. Hit the macros, prioritize whole foods for ~80% of intake, and the flexibility of the remaining 20% makes the diet sustainable.