The Macro Split Calculator converts a daily calorie target into grams of protein, carbohydrate and fat for the ratio you choose. It is the quick bridge between “I want 2,000 calories” and “so that’s how many grams of each macro” — and it runs entirely in your browser.
How the maths works
Each macronutrient has a known energy density (the Atwater values):
| Macro | Calories per gram |
|---|---|
| Protein | 4 kcal/g |
| Carbohydrate | 4 kcal/g |
| Fat | 9 kcal/g |
The calculator splits your calorie target by the chosen percentages, then divides each portion by its kcal-per-gram to get grams. For example, 2,000 kcal on a 30/40/30 split gives 150 g protein, 200 g carbs and ~67 g fat.
Choosing a split
- Balanced (30/40/30) — a sensible default for most people.
- High protein (40/30/30) — supports muscle retention in a calorie deficit.
- Low carb (40/20/40) — favoured by some fat-loss approaches.
- Endurance (25/55/20) — more carbohydrate to fuel long training.
This is educational information, not medical advice — consult a professional for a personalised plan. Everything is calculated locally in your browser.
When to use this calculator vs. a TDEE calculator
This tool answers a specific question: “Given X calories per day, how many grams of each macro does my chosen split translate to?” It does not estimate how many calories you should eat — that requires a TDEE or calorie-deficit calculator. Use this tool as the second step after you have a calorie target, to turn an abstract calorie number into concrete daily gram goals you can track in a food diary or app.
Why grams of fat are always lower than grams of protein or carbs
At the same calorie allocation, fat always produces fewer grams because it is more than twice as calorie-dense as protein or carbohydrate. For example on a 2,000 kcal day with a 30/40/30 split:
- Protein share: 600 kcal ÷ 4 kcal/g = 150 g
- Carb share: 800 kcal ÷ 4 kcal/g = 200 g
- Fat share: 600 kcal ÷ 9 kcal/g = 67 g
The fat allocation is less than half the grams of either protein or carbs, even though it receives 30% of calories just like protein. This surprises people who are used to thinking in grams rather than calories, and it is why “high fat” diets like keto look very different in total food volume versus calorie share.
Adjusting for your body weight: checking protein adequacy
After calculating your macros, check the protein gram figure against your body weight. A commonly cited guideline for people doing resistance training is around 1.6 g of protein per kilogram of body weight. For a 70 kg person that is 112 g; for a 90 kg person it is 144 g. If your calculated protein grams fall below this range, consider shifting the split toward higher protein — increase protein percentage, decrease carbs or fat to keep calories constant.
Tracking macros in practice
Once you have daily gram targets, you need to match food to them. Common approaches:
- A food tracking app (many free options exist) lets you scan barcodes and log meals, showing running totals against your daily goals
- Meal prep: planning and cooking meals in advance makes hitting targets consistent; a meal that hits roughly 40 g protein, 50 g carbs, and 15 g fat is easy to prepare in bulk
- Rough portion estimates: over time, experienced trackers can estimate macros without logging every meal — protein in particular becomes intuitive (roughly 25–35 g per palm-sized portion of meat or fish)
Perfect daily accuracy is not necessary. What matters is hitting your targets on average across a week, not on every single day.