Character sheet
Your base stats
- Build readingBody mass index (BMI)
- Resting regenBasal metabolic rate
- Stamina poolDaily energy use
- Daily rationDaily energy target
- RepairProtein
- FuelCarbohydrate
- ReserveFat
Where the energy target comes from
Protein Carbohydrate Fat
For anyone under 18, BMI is read against growth charts for age and sex, which this calculator does not have, and the energy formulas are made for adults. So it shows the number alone. A doctor or school nurse can read it properly.
A BMI under 18.5 is below the WHO adult range. Before eating less to lose weight, talk to a doctor; and if food or weight has become a struggle, the Academy for Eating Disorders lists help by country.
BMI is a rough screening number and no clear indication of your health (see why). These are estimates from published formulas, not medical advice.
How the numbers are made
Basal metabolic rate is the energy your body uses at rest, from the Mifflin-St Jeor equation (1990): 10 × weight in kg + 6.25 × height in cm − 5 × age, plus 5 for men and minus 161 for women. With sex not stated, the calculator uses the lower constant, which gives the more cautious answer.
Daily energy use is the basal rate times an activity factor:
| Activity | Looks like | Factor |
|---|---|---|
| Sedentary | Desk job, little movement | × 1.2 |
| Light | Light exercise 1 to 3 days a week | × 1.375 |
| Moderate | Exercise 3 to 5 days a week | × 1.55 |
| Active | Hard exercise 6 to 7 days a week | × 1.725 |
| Very active | Physical job or twice-daily training | × 1.9 |
The daily energy target adjusts daily energy use for your goal, and the protein each goal asks for is set by body weight:
| Goal | Energy target | Protein per kg of body weight |
|---|---|---|
| Maintain | your daily energy use | 1.6 g |
| Lose fat | 20% under your daily energy use | 2 g |
| Recomp | 5% under your daily energy use | 1.8 g |
| Build muscle | 10% over your daily energy use | 1.8 g |
Fat gets at least 0.6 g per kilogram, and carbohydrate fills what is left of the target. These are the formulas the StatBlockFit app uses for its own targets; the calculator runs the app's code.
The floor it never goes under
Whatever the goal, the target is never lower than the greater of your basal metabolic rate and 1,200 kcal for women or 1,500 kcal for men (1,500 kcal when sex is not stated). If a goal asks for less, the calculator raises it and says so. Nothing here rewards eating less: losing fat asks for more protein, not for a bigger deficit.
If food or weight has become a struggle, the Academy for Eating Disorders lists help by country.
About BMI, and why it is a weak measure
Body mass index is your weight in kilograms divided by your height in metres squared. The calculator shows it correctly, to one decimal, because it is widely used and you may be asked for it. It is no clear indication of your health:
- It cannot see muscle. A trained lifter and a sedentary person of the same height and weight get the same number.
- It cannot see where fat sits, and fat around the waist matters more than the total.
- It shifts with age, sex and ancestry. The same number means different things for different people, which is why some countries use other cut-offs.
- It is not for everyone. It does not apply in pregnancy, and for under-18s it is read against growth charts, not the adult scale.
The WHO's adult scale is below for reference. The calculator places your number on it and names no category for you.
| BMI | What the WHO adult scale calls it |
|---|---|
| Under 18.5 | Underweight |
| 18.5 to 24.9 | Normal weight |
| 25 to 29.9 | Overweight |
| 30 and over | Obesity |
A doctor reads BMI together with waist size, blood pressure, blood tests and how you feel. Use it the same way: as one number among several, and not as a verdict.
Your character sheet
The result is laid out as a character sheet: the build reading, the resting regen, the stamina pool, the daily ration and the three macros. Download it as a picture to keep or share; it is drawn on your device and saved only where you save it.
Questions
Is BMI accurate?
As a number it is exact: weight in kilograms divided by height in metres squared. As a measure of one person's health it is not reliable. It cannot tell muscle from fat, says nothing about where fat sits, and the same number means different things at different ages, for different sexes and in different populations. It is a screening tool for groups, not a diagnosis.
How many calories do I burn a day?
An estimate is your basal metabolic rate, from the Mifflin-St Jeor equation, multiplied by an activity factor between 1.2 and 1.9. Real use varies by a few hundred kilocalories either way; a few weeks of logging your intake and weight tells you more than any formula.
How much protein do I need?
StatBlockFit's targets ask for 1.6 g per kilogram of body weight to maintain, 1.8 g to build muscle or recompose, and 2 g while losing fat, because protein protects muscle while you eat less.
Why will it not give me a lower calorie target?
The target never goes below the greater of your basal metabolic rate and 1,200 kcal (female) or 1,500 kcal (male, or not stated). Eating below that is not something a fitness app should prescribe.
Is this medical advice?
No. It is general information from published formulas. If you are pregnant, under 18, have a medical condition or have had an eating disorder, talk to a doctor or a registered dietitian before you change how you eat.