How the split is built
The calculator starts from your TDEE (Mifflin-St Jeor × activity), applies the goal adjustment, then allocates in a fixed order: protein first — 1.6 g/kg at maintenance, rising to 2.0 g/kg on a cut, where holding muscle matters most; fat second at 25% of calories, enough for hormones and satiety; carbs take whatever is left, because they are the flexible fuel. This protein-first ordering is what sports-nutrition position stands actually recommend.
Why protein goes up when calories go down
In a deficit your body will happily burn muscle along with fat unless given a reason not to. Higher protein plus resistance training is that reason — it is the difference between losing weight and losing fat. On a bulk the requirement relaxes slightly because the surplus itself is protective.
Hitting the numbers in practice
Do not chase gram-perfect days. Land within ±10 g on protein and let carbs and fat trade off against each other freely — total calories and protein are the two numbers that drive results. The per-meal line above is there to make the daily total feel concrete, not to schedule your life.
Frequently asked questions
Do I need to hit my macros exactly every day?
No. Calories and protein drive almost all of the result; carbs and fat can swap freely within the calorie budget. Weekly averages beat daily perfection.
Why 4 kcal per gram for carbs and protein but 9 for fat?
Those are the Atwater factors — the standard energy densities used on food labels worldwide. Fat simply stores more than twice the energy per gram, which is why small amounts of oil move the calorie count so much.
Is this medical advice?
No. Standard ratios for each goal, which are starting points rather than prescriptions. Diabetes, kidney conditions and pregnancy all change what these ratios should be.
Is my data stored or sent anywhere?
No. Your intake targets stay in the browser and are not stored.
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