🥗 Macro Calculator
Turn a daily calorie target into grams of protein, carbohydrate and fat. Pick a split that matches your goal, or set your own protein target and let the rest follow.
Turning calories into grams of protein, carbs and fat
Calories decide whether you gain or lose. Macronutrients decide what you gain or lose, how full you feel, and how you perform. Two 2,400-calorie days with very different macro splits produce different body composition over months, even when the scale moves identically.
The energy each macro provides
| Macro | kcal/g | Primary role |
|---|---|---|
| Protein | 4 | Builds and preserves tissue; most satiating |
| Carbohydrate | 4 | Primary fuel for hard training and the brain |
| Fat | 9 | Hormone production, vitamin absorption, slow fuel |
| Alcohol | 7 | No nutritional role; counts towards the total |
Fat carries more than twice the calories per gram, which is why fat grams look small next to carb grams on the same split. Thirty per cent of 2,400 calories is 720 kcal, which is 80 g of fat but would be 180 g of carbohydrate.
Common splits and who they suit
| Split (P/C/F) | Suits |
|---|---|
| 40 / 30 / 30 | Cutting: high protein preserves muscle and keeps you full |
| 30 / 40 / 30 | Maintenance and general health |
| 30 / 45 / 25 | Building muscle: carbs fuel the training that drives it |
| 35 / 20 / 45 | Low carb, for people who prefer it or respond well to it |
| 25 / 55 / 20 | Endurance training, where glycogen is the limiting factor |
These are conventions, not physiology. Adherence beats optimisation: the split you can follow for six months outperforms the theoretically ideal one you abandon in three weeks.
Protein first, then fat, then carbs fill the gap
A more reliable method than percentages. Set protein at 1.6 to 2.2 grams per kilogram of body weight, which is where the evidence for muscle preservation sits. Set fat at a minimum of 0.6 to 0.8 g per kg to protect hormonal function. Whatever calories remain become carbohydrate. This keeps protein and fat at sensible absolute amounts regardless of your calorie target, which percentage splits do not.
For an 80 kg person at 2,400 calories: protein 160 g (640 kcal), fat 64 g (576 kcal), leaving 1,184 kcal, so 296 g of carbohydrate.
Where the numbers come from
- Protein 1.6–2.2 g/kg. Meta-analyses find muscle-protein synthesis plateaus around 1.6 g/kg for most people, with the upper end relevant during a deficit or for trained lifters.
- Fat above 0.6 g/kg. Very low fat intakes are associated with reduced testosterone and impaired absorption of fat-soluble vitamins.
- Carbohydrate as the remainder. It is not essential in the biochemical sense, but it is the most useful fuel for intense training and the easiest lever to adjust.
- Fibre 25–35 g. Counted inside the carbohydrate total, and the component most often short on a low-carb split.
Tracking without losing your mind
Hitting macros within about 10 grams is close enough; the precision of food labels does not justify more. Most people find it easier to track protein carefully and let carbs and fat land where they fall, since protein is the one with a clear target and the one most often missed. Two weeks of honest tracking also teaches you the composition of the foods you eat repeatedly, after which you can estimate most days accurately.
A worked example
An 80 kg person on 2,400 calories using the protein-first method: 1.9 g/kg gives 152 g of protein (608 kcal), fat at 0.8 g/kg gives 64 g (576 kcal), and the remaining 1,216 kcal gives 304 g of carbohydrate. A 40/30/30 percentage split on the same calories would demand 240 g of protein, which is 3 g/kg and considerably more than the evidence supports.
This page explains published formulas and population averages. It is general information, not medical advice. Talk to a doctor or a registered dietitian before changing how you eat or train.
Frequently Asked Questions (FAQs)
How much protein do I actually need?
For general health, around 0.8 g per kg is the minimum. For preserving muscle while losing weight, or for building it, 1.6 to 2.2 g per kg is the range the evidence supports. Beyond about 2.4 g/kg there is no additional benefit, though no harm either for healthy kidneys.
Do macros matter if I hit my calories?
For weight, calories dominate. For body composition, performance and hunger, macros matter a great deal. Two people losing the same weight can lose very different amounts of muscle depending on protein intake and whether they train.
Is low carb better for fat loss?
Not inherently. Controlled studies matching calories and protein find little difference in fat loss between low-carb and higher-carb diets. Low carb suits people who find it more satiating; the early rapid loss is mostly water bound to glycogen.
Should I eat the same macros on rest days?
You can, and the simplicity helps adherence. Some people prefer carb cycling, with more carbohydrate on training days and more fat on rest days, keeping protein and weekly calories constant. The evidence for an advantage is thin, but it suits some schedules.
Does the timing of my macros matter?
Much less than total daily intake. The old anabolic window idea has not held up: protein distributed reasonably across the day matters more than hitting a thirty-minute post-workout slot. Carbohydrate timing matters more for athletes training twice a day.
How do I count alcohol?
At 7 calories per gram, and against your total. A standard drink is roughly 100 to 150 calories with no useful macros. Most tracking apps log it as carbohydrate, which is wrong chemically but works for energy balance.