What this tool does
You bring a calorie budget and three percentages. The tool converts them with 4 kcal/g for protein and carbohydrate and 9 kcal/g for fat. It does not secretly rebalance a sloppy 120% total — that mismatch will show up as an incoherent plate.
How it works
Each macro’s grams = (calories × percent) ÷ kcal per gram. That is accounting, not physiology. Sports nutrition usually sets protein in grams per kilogram first, then lets carbs and fat share what remains. Use the protein calculator if you lift or cut.
Formula and methodology
Protein g = kcal × protein% / 4; carbohydrate g = kcal × carb% / 4; fat g = kcal × fat% / 9. Atwater factors are averages. High-fiber or high-alcohol days will not match a clean 4-4-9 ledger.
How to interpret the result
If protein percent yields only 0.6 g/kg, the split is fashion, not a training diet. If fat is under ~15–20% of calories for a long stretch, hormones and palatability often suffer. Endurance blocks may want the carb percentage high without calling it a new identity.
Example
At 2,200 kcal with 30/40/30: protein 165 g, carbohydrate 220 g, fat 73 g. For an 80 kg lifter, 165 g is about 2.1 g/kg — a solid cut or muscle range. The same percents at 1,600 kcal drop protein to 120 g, which may be too low unless body weight is smaller.
Common mistakes
- Percentages that do not add to 100.
- Copying a 40/40/20 influencer split onto a 1,400 kcal budget and wondering why protein collapsed.
- Treating alcohol as free because it is not a named field.
- Changing percents daily instead of repeating a split you can cook.
When this estimate may be off
- The calorie target itself is wrong, so every gram inherits the error.
- You need clinical keto, renal, or diabetic carbohydrate prescriptions this page does not encode.
- A large share of calories is alcohol or sugar alcohols with different energy yields.
- Food labels round, so logged grams will not match the spreadsheet exactly.