Macro Calculator: Protein, Carbs & Fat
Estimate an adult calorie starting point and protein, carbohydrate and fat grams from body details, activity and a goal preset.
Useful next calculators
On this page
What this calculator estimates
Estimate an adult calorie starting point and protein, carbohydrate and fat grams from body details, activity and a goal preset. The form does not accept a custom calorie intake or preferred macro split.
Inputs and calculation method
Enter age, equation option, height in cm, weight in kg, activity and maintenance, loss or gain. The tool estimates maintenance with Mifflin–St Jeor × activity, then applies the selected goal’s fixed energy and protein settings. Fat is 28% of calculated energy; carbohydrate receives the remainder.
Formula and units
Goal energy = estimated maintenance + 0 kcal for maintenance, − 350 for loss or + 250 for gain. Protein = weight × 1.6, 1.8 or 2.0 g/kg for those goals respectively. Fat = goal kcal × 0.28 ÷ 9. Carbohydrate = max(0, (goal kcal − protein × 4 − fat × 9) ÷ 4). Results are rounded to whole kcal and grams.
How to use it
- Enter adult body details and select the equation option.
- Choose the activity category for a typical week.
- Choose maintenance, loss or gain and calculate.
- Read the maintenance comparison and all three macros together, including the preset assumptions.
Worked example
For age 35, 165 cm, 70 kg, the female equation and Moderate activity, maintenance is 2,162.64 kcal/day. Maintenance mode shows about 2,163 kcal, 112 g protein, 277 g carbohydrate and 67 g fat. Loss mode uses about 1,813 kcal, 126 g protein, 200 g carbohydrate and 56 g fat. These are preset comparisons, not individually prescribed diets.
How to read the result
Rounded macro grams may not reproduce the displayed energy exactly when multiplied by 4, 4 and 9. The loss and gain labels apply fixed adjustments; they do not assess your intended timeline or predict weight change.
Common mistakes
- Assuming the form includes a custom macro split.
- Combining grams from one goal with calories from another.
- Treating the fixed deficit or surplus as appropriate for every adult.
Method limitations
The energy equation and presets do not assess medical nutrition, pregnancy, growth or individual sport demands. If fixed protein and fat consume the available calories, carbohydrate is held at zero; that boundary is a calculation safeguard, not a recommended diet.
Sources and method references
Calculation assumptions
The calculator estimates resting energy with the Mifflin–St Jeor equation, applies the selected activity factor, then adjusts estimated maintenance calories by 350 calories for fat loss or 250 calories for muscle gain.
Protein is set from body weight at 1.6 g/kg for maintenance, 1.8 g/kg for fat loss and 2.0 g/kg for muscle gain. Fat is set at 28% of the calorie estimate and carbohydrate receives the remaining calories. These are general planning settings, not personalised dietetic advice.
Macro Calculator: Protein, Carbs & Fat FAQs
Can I enter my own calorie target or split?
No. This version derives calories from body details and uses the displayed goal presets.
Why does protein change with the goal?
Maintenance uses 1.6 g/kg, loss 1.8 and gain 2.0. They are fixed settings in this tool.
Why do the rounded macros not total exactly the displayed calories?
Calories and each gram value are rounded separately. Use the unrounded formula to reproduce the calculation.
Is the loss preset the same as every other calorie tool?
No. This page subtracts 350 kcal. Other tools can use different illustrative adjustments or weekly-rate assumptions.
Using the estimate
Use the output as one explicit set of adult planning presets. Keep its estimated maintenance, goal adjustment and macro assumptions together.