Plot No. 45 · Health & Fitness
Macronutrient Calculator
Split a daily calorie target into grams of protein, carbs and fat. Pick a ratio, then the calculator takes the share of calories for each macro and divides by its energy density: 4 kcal per gram for protein and carbs, 9 kcal per gram for fat. It assumes you already know your calorie goal.
Macros are derived from the calorie target you enter, not from your body stats. These are estimates, not medical advice.
The link saves your inputs so you can bookmark or share this exact result.
Calories per gram of protein, carbohydrate and fat (the 4-4-9 rule)
Protein and carbohydrate each supply 4 calories per gram and fat supplies 9. These round figures are the general Atwater factors, and they are the ones the US Food and Drug Administration lists as a permitted way to work out the calorie line on a Nutrition Facts label (21 CFR 101.9(c)(1)(i)). UK and EU labels use the same values, stated in kilojoules as well. They are also the only factors the calculator above uses, which is why fat grams always look small next to the other two: the same share of calories buys fewer than half as many grams.
| Energy source | kcal per gram | kJ per gram (UK/EU) | Grams in 100 kcal |
|---|---|---|---|
| Protein | 4 | 17 | 25.0 g |
| Carbohydrate | 4 | 17 | 25.0 g |
| Fat | 9 | 37 | 11.1 g |
| Alcohol (not a macro here) | 7 | 29 | 14.3 g |
| Fibre (UK/EU labels) | 2 | 8 | 50.0 g |
The kilojoule values are the conversion factors in Annex XIV of EU Regulation 1169/2011, which the UK retained. US rules also allow food-specific factors, a reduced value for soluble fibre and sugar alcohols, and zero for insoluble fibre, so a label can legitimately differ from a straight 4-4-9 sum.
Macros in grams at common calorie targets
Each cell is the calculator above run on that calorie target, shown as protein / carbohydrate / fat in grams per day. The three splits are the calculator's presets: balanced is 40/30/30, low-carb is 25/35/40 and high-protein is 35/40/25, as percentages of calories from carbs, protein and fat. If you do not yet have a calorie target, the BMR and calorie calculator gives you a maintenance figure to start from.
| Calories per day | Balanced (P / C / F) | Low-carb (P / C / F) | High-protein (P / C / F) |
|---|---|---|---|
| 1,200 kcal | 90 g / 120 g / 40 g | 105 g / 75 g / 53 g | 120 g / 105 g / 33 g |
| 1,500 kcal | 113 g / 150 g / 50 g | 131 g / 94 g / 67 g | 150 g / 131 g / 42 g |
| 1,800 kcal | 135 g / 180 g / 60 g | 158 g / 113 g / 80 g | 180 g / 158 g / 50 g |
| 2,000 kcal | 150 g / 200 g / 67 g | 175 g / 125 g / 89 g | 200 g / 175 g / 56 g |
| 2,200 kcal | 165 g / 220 g / 73 g | 193 g / 138 g / 98 g | 220 g / 193 g / 61 g |
| 2,500 kcal | 188 g / 250 g / 83 g | 219 g / 156 g / 111 g | 250 g / 219 g / 69 g |
| 2,800 kcal | 210 g / 280 g / 93 g | 245 g / 175 g / 124 g | 280 g / 245 g / 78 g |
| 3,000 kcal | 225 g / 300 g / 100 g | 263 g / 188 g / 133 g | 300 g / 263 g / 83 g |
| 3,500 kcal | 263 g / 350 g / 117 g | 306 g / 219 g / 156 g | 350 g / 306 g / 97 g |
Grams are rounded to whole numbers, so multiplying a row back out by 4-4-9 can land a few calories off the target. Protein needs are usually set from body weight rather than as a share of calories; the protein intake calculator does it that way, and is worth cross-checking against the protein column here.
Checking a nutrition label with 4-4-9
The same factors run in reverse turn grams back into calories: multiply protein and carbohydrate grams by 4, fat grams by 9, and add them up. That is a quick way to sanity check a label or a food log. The last column shows how that sum would appear on a US label, which rounds the calorie line to the nearest 5 up to 50 calories and to the nearest 10 above 50. The foods are illustrative round numbers, not values for any particular product.
| Food | Protein | Carbs | Fat | 4-4-9 total | Label shows |
|---|---|---|---|---|---|
| Plain yoghurt pot | 10 g | 30 g | 5 g | 205.0 kcal | 210 kcal |
| Chicken breast, 100 g cooked | 31 g | 0 g | 3.6 g | 156.4 kcal | 160 kcal |
| Slice of wholemeal bread | 4 g | 17 g | 1 g | 93.0 kcal | 90 kcal |
| Tablespoon of olive oil | 0 g | 0 g | 13.5 g | 121.5 kcal | 120 kcal |
If your own sum is well away from the printed figure, the usual reasons are fibre (counted at 2 kcal per gram or less rather than 4), sugar alcohols in "low sugar" products, or a manufacturer using food-specific factors. US rules treat a product as misbranded only when its real calories run more than 20 percent above the label.
How macros are worked out from calories
This calculator splits a calorie target you already have into grams of protein, carbohydrate and fat. It does not estimate how many calories you need; it assumes you bring that number, for example from a BMR and calorie calculator, and divides it up. Each macro is given a percentage share of the calories based on the ratio you pick.
To turn calories into grams it divides by each macro's energy density: 4 kcal per gram for protein and carbohydrate, and 9 kcal per gram for fat. So protein grams equal calories times the protein percentage divided by 100, divided by 4, and fat grams use the same idea but divided by 9 because fat packs more energy per gram.
How to use the macro calculator
- Enter your daily calorie target; if you do not know it, work out maintenance with a calorie calculator first.
- Choose a split: balanced, low-carb or high-protein, each of which sets the percentage of calories from carbs, protein and fat.
- Read the grams of protein, carbohydrate and fat to aim for each day.
Worked examples
Balanced split
Inputs: 2,200 kcal, balanced (40% carbs / 30% protein / 30% fat)
Result: About 165 g protein, 220 g carbohydrate and 73 g fat per day.
High-protein split
Inputs: 2,200 kcal, high-protein (35% carbs / 40% protein / 25% fat)
Result: About 220 g protein, 193 g carbohydrate and 61 g fat per day.
Limitations and common mistakes
Edge cases and limitations
- Grams are rounded to whole numbers, so the calories implied by the rounded grams may differ slightly from your target.
- It uses fixed preset ratios rather than letting you set custom percentages.
- It splits calories only; it does not judge whether your calorie target itself is right for your goal.
Common mistakes
- Using this as a calorie calculator; it needs a calorie number as input, it does not produce one.
- Forgetting that fat is 9 kcal per gram, which is why its gram total looks small next to carbs and protein.
Frequently asked questions
How are macros worked out from calories?
Each macro gets a share of your calories, then that share is divided by its energy density. On a 2,200 kcal balanced split (40 percent carbs, 30 percent protein, 30 percent fat) you get about 220 g carbs, 165 g protein and 73 g fat per day.
Do I need to know my calorie target first?
Yes. This tool only splits a number you already have. If you do not know your daily calories, work out your maintenance figure with a BMR and calorie calculator first, then bring that number here to divide it into grams.
Which split should I choose?
Balanced suits most general goals, low-carb shifts energy toward fat and protein, and high-protein favours muscle retention while dieting. None is magic; total calories drive weight change, and the split mainly affects fullness, training fuel and how easy the plan is to stick to.
How many calories per gram are in protein, carbohydrate and fat?
4 calories per gram for protein, 4 for carbohydrate and 9 for fat. These are the general factors the US FDA allows for the calorie line on a Nutrition Facts label, often called the 4-4-9 rule. Alcohol, which is not a macro in this calculator, supplies 7 calories per gram.
Why do my macros not add up to the calories on the nutrition label?
Labels round the calorie line, to the nearest 5 up to 50 calories and the nearest 10 above that, and manufacturers may use other permitted methods, such as food-specific factors or counting fibre at 2 calories per gram or less. A gap of a few percent is normal, and US rules allow real calories to run up to 20 percent above the declared figure.
How many grams of protein is 30 percent of 2,000 calories?
150 grams. 30 percent of 2,000 is 600 calories, and at 4 calories per gram that is 600 divided by 4. The same share of calories as fat would be only about 67 grams, because fat carries 9 calories per gram.
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