Macro calculator
Protein and fat come from your bodyweight, so this doubles as a straight protein calculator if that is all you need. Carbs get whatever energy is left. Put your numbers in and you get all three in grams, with the reason each one landed where it did. It is the same derivation the app runs, from the same shared code.
The Mifflin-St Jeor equation has separate constants for each, which is why it asks.
Why this split and not a percentage
Most macro calculators hand you percentages: 40/30/30, or whatever the current fashion is. Percentages scale with your calories. That is exactly backwards. Your protein requirement does not fall because you decided to eat less this week. It is set by how much of you there is.
So protein is fixed at 1.6 g per kg and fat at 0.8 g per kg, and carbohydrate takes the remainder. On a bigger day you get more carbs. On a smaller day you get fewer. The two numbers that protect your body stay still.
Common questions
- How do I calculate my macros?
- Set protein from bodyweight, set fat from bodyweight, and give carbs whatever energy is left. This calculator uses 1.6 g of protein and 0.8 g of fat per kg, then fills the rest with carbs at 4 kcal a gram.
- How much protein do I need to lose fat?
- Around 1.6 g per kg of bodyweight. That is enough to hold on to the muscle you have while you lose fat, which is the whole job protein does on a deficit. For a 78 kg person that is about 125 g a day.
- What does it mean for fat to be a floor?
- Fat below roughly 0.8 g per kg starts to affect hormone production and how well you absorb fat-soluble vitamins. Treat it as a boundary to respect. Hitting the exact gram count matters far less.
- Why do carbs get whatever is left?
- Because carbs are the flexible one. Protein and fat are set by your body, so they barely move. Carbs absorb the difference. That is the mechanism that lets you keep bread, rice or pasta on the plate in a deficit.
- Do I have to hit my macros exactly?
- No. Get protein close, keep fat above the floor, and let the rest sit where it lands. Chasing three numbers to the gram is how people burn out in week three.
- What macro split is best for weight loss?
- Total calories decide whether you lose weight. The split decides how much of the loss is fat rather than muscle, and how tolerable the diet is. Protein high, fat adequate, carbs flexible covers both.
Numbers are the easy part.
Hitting them at 7pm with what is actually in your kitchen is the hard part. That is what the coach is for.
