Macro Calculator
Calories decide whether you gain or lose. Macros decide what you gain or lose, how well you train, and how manageable the whole thing feels.
How the split is decided
The calculator does not start from percentages. It sets protein and fat from your body weight — because those are the two with genuine minimum requirements — and lets carbohydrate take whatever calories remain.
Protein rises in a deficit rather than falling, which surprises people. The reason is that its main job during a cut is protecting lean tissue, and that job gets harder as calories drop. Protein is also the most satiating macronutrient and has the highest thermic effect — roughly 20–30 % of its energy is spent digesting it, against 5–10 % for carbohydrate and 0–3 % for fat.
Why fat has a floor
Dietary fat is not optional. Below roughly 0.5 g per kilogram of body weight, several things start to go wrong: absorption of vitamins A, D, E and K is impaired, essential fatty acid intake falls short, and sex hormone production is affected in both sexes — testosterone in men, menstrual regularity in women.
The 0.8 g/kg floor used here gives comfortable headroom above the problem zone while leaving room for carbohydrate. If your calories are low enough that protein and fat alone consume the entire budget, the calculator reduces fat towards a floor rather than letting carbohydrate go negative.
What carbohydrate is for
Carbohydrate is the only macronutrient with no absolute dietary requirement — the body can make glucose from protein and glycerol. That fact is often stretched into the claim that carbohydrate does not matter. For anyone who trains, it does:
- It refills muscle glycogen, the dominant fuel for anything above moderate intensity.
- It supports training volume. Low-carbohydrate training tends to mean fewer quality sets.
- It is protein-sparing: adequate carbohydrate means less amino acid diverted to energy.
- It carries most of the fibre and a good deal of the micronutrient content of a normal diet.
Within a fixed calorie and protein budget, the carbohydrate-to-fat ratio is largely a preference question. Both low-fat and low-carbohydrate approaches produce equivalent fat loss in controlled trials when protein and calories are matched. Choose the one you can actually stick to.
Tracking without losing your mind
Three rules make macro tracking sustainable rather than obsessive:
- Prioritise protein. If you hit your protein and your calories, the rest is optimisation. Fat and carbohydrate can vary day to day without consequence.
- Weigh food raw where it matters. Rice roughly triples in weight when cooked; meat loses around 25 %. Database entries usually assume raw.
- Count cooking oil. A tablespoon of olive oil is 120 kcal. Untracked oils and dressings are the single most common reason a carefully tracked diet does not work.
Accept a margin of ±5 % on each macro. Chasing the last gram adds stress and changes nothing.
Frequently asked questions
Does the exact macro split matter for fat loss?
Far less than total calories and adequate protein. Trials matching calories and protein find no meaningful difference in fat loss between low-carb and low-fat approaches. Pick the split that keeps you full and lets you train well.
Can I eat more protein than this?
Yes, within reason. Intakes up to about 3 g/kg are safe for people with healthy kidneys and can help with satiety during a deficit. There is no added muscle-building benefit above roughly 2.2 g/kg, so the extra is a preference rather than a requirement.
Should I change macros on rest days?
Only if you want to. Some people prefer lower carbohydrate on rest days and higher on training days at the same weekly total. It is a legitimate approach but it is not necessary, and it adds complexity that many find harder to sustain.
Do fibre and alcohol count?
Fibre is a carbohydrate but contributes little usable energy; most tracking apps handle this automatically. Alcohol supplies 7 kcal per gram, fits into none of the three macros, and suppresses fat oxidation while it is being metabolised. Count its calories.