Calorie & Macro Calculator
For adults (18+). Estimate how much energy your body uses each day, and a simple split of protein, fat and carbohydrates.
Calculate your needs
What the numbers mean
- Calories: the energy your body uses for everything — breathing, thinking, moving.
- Protein: builds and repairs muscles and other tissues.
- Carbohydrates: your body's main, quickest fuel.
- Fat: long-lasting energy, and needed to absorb some vitamins.
Remember: these numbers are a starting point, not a rule.
How Do We Calculate Your Calories?
Step 1 — resting energy (BMR). We use the Mifflin-St Jeor equation (1990). It estimates the energy you use at rest from your weight, height, age and sex. A review that compared the main equations found it was the most reliable for healthy adults, both with and without obesity (Frankenfield, 2005).
Step 2 — activity. We multiply by an activity factor (1.2 for mostly sitting up to 1.725 for hard daily exercise). These factors are rough, so this is the least precise step.
Step 3 — goal. To lose weight we subtract 500 kcal a day; to gain, we add 300 kcal. Then we split the calories 25% protein, 25% fat and 50% carbohydrates. This split sits inside the ranges experts consider acceptable for adults (protein 10–35%, fat 20–35%, carbohydrates 45–65%).
| Equation | What it does | Used here? |
|---|---|---|
| Mifflin-St Jeor | Estimates resting energy from weight, height, age, sex | Yes |
| Harris-Benedict | Older equation (1919), less accurate in comparisons | No |
| Katch-McArdle | Uses lean body mass, if you know your body fat | No |
How fast does weight really change?
You may have heard "cut 500 kcal a day and lose 1 pound (0.45 kg) a week". That old rule is too optimistic over time: as you lose weight, your body uses less energy, so weight loss slows down. Researchers at the NIH built a better model (Hall, 2011) — you can try it with the free NIH Body Weight Planner.
The CDC suggests aiming for about 1 to 2 pounds (0.5 to 1 kg) a week. People who lose weight at this steady pace are more likely to keep it off.
Are all calories the same?
For energy, yes. For your health and hunger, no. 500 kcal of vegetables, beans or whole grains bring fiber, vitamins and minerals and keep you full longer than 500 kcal of sweets.
Handy Reference Table
| Common foods | Calories (approx.) |
|---|---|
| Apple (1 medium) | 95 |
| Banana (1 medium) | 105 |
| Chicken breast (3 oz / 85 g, cooked) | 140 |
| White rice (1 cup cooked) | 205 |
| Broccoli (1 cup, chopped) | 30 |
| Bread (1 slice) | 80 |
| Cheddar cheese (1 oz / 28 g) | 115 |
| Egg (1 large) | 70 |
| Orange juice (1 cup) | 110 |
Values vary by size and brand. Look up exact values at USDA FoodData Central.
How to track calories
- Apps (like MyFitnessPal, Cronometer, Yazio)
- Food labels
- A simple food diary
Tip: rough tracking is enough to notice your habits. You do not need to be perfect.
Frequently Asked Questions
Calculators use different equations and activity factors. All of them are estimates.
No. The equation was built for adults, and children and teens need energy to grow. Please ask a doctor or dietitian.
The Mifflin-St Jeor equation was built from male and female data only. If neither fits you, a dietitian can help you choose.
Please talk to a doctor or registered dietitian for personal advice.
Sources
- Mifflin MD et al. A new predictive equation for resting energy expenditure. Am J Clin Nutr. 1990
- Frankenfield D et al. Comparison of predictive equations for resting metabolic rate. J Am Diet Assoc. 2005
- Institute of Medicine – Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005), incl. acceptable macronutrient ranges
- Harvard Health Publishing – Calorie counting made easy
- Hall KD et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011
- NIH (NIDDK) – Body Weight Planner
- CDC – Losing weight
Last reviewed 2026-09-26.