Macro Calculator
Calculate your estimated daily calories, protein, carbohydrates, and fat based on your age, sex, height, weight, activity level, and goal.
FitZio Macro Calculator
Enter your information below. You can switch between metric and imperial height and weight units.
Macro Breakdown
| Macro | Grams/day | Calories | % of calories |
|---|---|---|---|
| Protein | — | — | — |
| Carbohydrates | — | — | — |
| Fat | — | — | — |
Results are estimates. Your actual calorie and macronutrient needs may differ.
What Is a Macro Calculator?
A macro calculator is a tool that estimates your daily macronutrient requirements. “Macros” is short for macronutrients: protein, carbohydrates, and fat.
These nutrients provide energy and have different roles in the diet. Protein and carbohydrates provide about 4 calories per gram, while fat provides about 9 calories per gram.
A macro calculator first estimates energy needs and then converts the calorie target into approximate amounts of protein, carbohydrates, and fat.
How the FitZio Macro Calculator Works
The calculator follows this sequence:
1. BMR
FitZio estimates resting energy expenditure with the Mifflin-St Jeor equation.
The original Mifflin-St Jeor research derived a predictive equation from measured resting energy expenditure in healthy adults. PubMed reference.
2. TDEE
Your estimated TDEE is calculated by multiplying BMR by an activity factor.
| Activity level | Factor |
|---|---|
| Sedentary | 1.20 |
| Lightly active | 1.375 |
| Moderately active | 1.55 |
| Very active | 1.725 |
| Extra active | 1.90 |
3. Goal Calories
| Goal | FitZio calculation |
|---|---|
| Maintain | TDEE |
| Lose weight | TDEE × 0.85 |
| Gain muscle / weight | TDEE × 1.10 |
These goal adjustments are the assumptions used by this calculator; they are not universal prescriptions.
4. Protein
FitZio uses 1.6 g/kg for maintenance and muscle gain, and 1.8 g/kg for weight loss.
The International Society of Sports Nutrition has described 1.4–2.0 g/kg/day as a range that can be appropriate for physically active individuals. ISSN position stand.
5. Fat
FitZio allocates 30% of target calories to fat:
This 30% allocation is a calculator assumption. The National Academies has historically described adult acceptable macronutrient distribution ranges rather than one universal macro ratio. National Academies reference.
6. Carbohydrates
Carbohydrates receive the remaining calories after protein and fat are allocated.
Example Macro Calculation
For a hypothetical 30-year-old man weighing 80 kg, standing 180 cm tall, moderately active, with a maintenance goal:
| Calculation | Result |
|---|---|
| BMR | 1,780 kcal/day |
| TDEE | ~2,759 kcal/day |
| Protein | 128 g/day |
| Fat | ~92 g/day |
| Carbohydrates | ~355 g/day |
Macro Calculator for Weight Loss
Select Lose weight to apply the FitZio weight-loss calculation. The calculator reduces estimated TDEE by 15% and uses 1.8 g/kg for protein.
This is a starting estimate. Your real-world energy needs can differ, so changes in body weight and activity should be considered over time.
Macro Calculator for Muscle Gain
Select Gain muscle / weight to apply a 10% increase above estimated TDEE. Protein is calculated at 1.6 g/kg.
A calorie surplus can support weight gain, but a calculator cannot predict exactly how much gained weight will be muscle.
Macro Calculator for Maintenance
Select Maintain weight to use your estimated TDEE as the calorie target. Your actual maintenance intake can be higher or lower because TDEE itself is an estimate.
How Accurate Is a Macro Calculator?
A macro calculator is a useful estimation tool, not a direct measurement of metabolism. The Mifflin-St Jeor equation is a predictive equation for resting energy expenditure, and research has shown that predictive equations have individual error.
Your real energy needs can vary with daily movement, exercise, training volume, body composition, weight changes, sleep, recovery, and individual metabolic differences.
For that reason, use the calculated result as a starting point and compare it with your real-world progress.
Do You Need to Hit Your Macros Exactly?
No. Macro targets are guidelines rather than numbers that must be perfect every day.
Food labels, portion sizes, cooking methods, restaurant meals, and nutrition databases all introduce measurement uncertainty. Consistently following a reasonable nutrition structure is generally more practical than trying to make every meal mathematically exact.
Important Limitations
People who are pregnant or breastfeeding, under 18, managing a medical condition, taking medications that affect appetite/metabolism/body weight, or dealing with an eating disorder or its history should seek individualized guidance from an appropriately qualified healthcare professional.
Frequently Asked Questions
What is a macro calculator?
A macro calculator estimates daily calories and the grams of protein, carbohydrates, and fat from personal information, activity level, and a selected goal.
How do I calculate my macros?
Estimate daily calorie needs, establish a protein target, allocate calories to fat, and use the remaining calories for carbohydrates. FitZio performs these calculations automatically.
How many grams of protein should I eat per day?
Protein needs vary with body size, activity, training status, and goals. This calculator uses 1.6 g/kg for maintenance and muscle gain and 1.8 g/kg for weight loss.
How many carbs should I eat per day?
Your carbohydrate result depends on your total calorie target and the calories allocated to protein and fat. In this calculator, carbohydrates receive the remaining calories.
How much fat should I eat per day?
The FitZio calculator allocates 30% of target calories to fat and converts those calories into grams using 9 calories per gram.
Can I use this macro calculator for weight loss?
Yes. Select Lose Weight. FitZio applies a 15% reduction to estimated TDEE and uses 1.8 g/kg for protein.
Can I use this calculator for muscle gain?
Yes. Select Gain Muscle / Weight. FitZio applies a 10% increase above estimated TDEE and calculates protein at 1.6 g/kg.
Are macro calculators accurate?
They provide estimates rather than direct measurements. Actual energy needs can differ because of activity, body composition, lifestyle, and individual metabolic differences.
Should I count macros or calories?
Both can be useful. Calories describe total energy intake, while macros describe how that energy is distributed among protein, carbohydrates, and fat.
Can I change my macro targets?
Yes. Your needs can change as your weight, activity, training volume, lifestyle, or goal changes. Recalculate when your circumstances materially change.
Related FitZio Tools
If you want to explore related nutrition and fitness calculations, FitZio also has dedicated tools covering calories, TDEE, BMR, calorie deficits, and protein.
References
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals.
- International Society of Sports Nutrition. Position stand: protein and exercise.
- National Academies. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements.
