Calorie Calculator Guide: Formula & Worked Example
Short answer
Daily calories to maintain, lose or gain weight. In the fixed example below, maintain weight is 2,267 kcal. Your answer depends on the inputs and assumptions you choose.
Formula
Mifflin-St Jeor BMR × activity factor
Use the relationship above with consistent units. The inputs are gender, age, weight, height, activity. Use the input scale shown beside each field and keep time periods and units consistent. Only round the final result for display.
Worked example
- Gender
- m
- Age
- 30
- Weight
- 70
- Height
- 175
- Activity
- 1.375
- Maintain weight: 2,267 kcal
- Mild loss (0.25 kg/wk): 2,017 kcal
- Weight loss (0.5 kg/wk): 1,767 kcal
- Extreme loss (1 kg/wk): 1,267 kcal
- Weight gain (0.5 kg/wk): 2,767 kcal
Understanding the result
Daily calories to maintain, lose or gain weight. Start with the base example, then replace each value with the figure that matches your situation.
Gender
The example uses Male for gender. This is an illustration, not a recommended value. Keep the unit and time period shown by the field.
Age
The example uses 30 years for age. This is an illustration, not a recommended value. Keep the unit and time period shown by the field.
Weight
The example uses 70 kg for weight. This is an illustration, not a recommended value. Keep the unit and time period shown by the field.
Height
The example uses 175 cm for height. This is an illustration, not a recommended value. Keep the unit and time period shown by the field.
Activity
The example uses Light (1–3 days/week) for activity. This is an illustration, not a recommended value. Keep the unit and time period shown by the field.
What the comparison means
The comparison changes only age, keeping every other example input fixed. This isolates that input's effect on the primary result. It does not predict future outcomes.
This is a screening or planning estimate, not a diagnosis. Age, pregnancy, medication and individual medical history can change how the result should be interpreted.
How calorie needs are estimated
- BMR (Mifflin-St Jeor): Men: 10 × kg + 6.25 × cm − 5 × age + 5. Women: 10 × kg + 6.25 × cm − 5 × age − 161.
- TDEE: multiply BMR by an activity factor.
| Activity level | Multiplier | |---|---| | Sedentary (little exercise) | 1.2 | | Light (1–3 days/week) | 1.375 | | Moderate (3–5 days/week) | 1.55 | | Very active (6–7 days/week) | 1.725 | | Extra active (physical job + training) | 1.9 |
Calories for weight goals
A deficit of about 500 calories a day is a common starting point for gradual weight loss of roughly 0.5 kg (1 lb) per week, though real results vary as the body adapts. For weight gain, a modest surplus of 250–500 calories with strength training favours muscle over fat.
People also ask
Which is more accurate, Mifflin-St Jeor or Harris-Benedict?
Research comparing the equations has generally found Mifflin-St Jeor closer to measured resting energy for most adults, which is why it is widely used today. Both are estimates.
Should I eat below my BMR?
Generally not without medical supervision. Very low intakes make it hard to get enough protein, vitamins and minerals.
Why am I not losing weight at my calculated deficit?
Common reasons are underestimated portions, overestimated activity, water retention and metabolic adaptation. Track for 2–3 weeks, then adjust intake by 100–200 calories.
How much protein do I need?
The Dietary Guidelines for Americans list the RDA as 0.8 g per kg of body weight for most adults; active people often aim higher. See dietaryguidelines.gov.
Comparison
| Scenario | Input | Result |
|---|---|---|
| Lower input | Age: 24 years | Maintain weight: 2,308 kcal |
| Base example | Age: 30 years | Maintain weight: 2,267 kcal |
| Higher input | Age: 36 years | Maintain weight: 2,226 kcal |
Common mistakes
- Using the wrong units for age.
- Comparing results while changing more than one input at a time.
- This is a screening or planning estimate, not a diagnosis. Age, pregnancy, medication and individual medical history can change how the result should be interpreted.
Checklist
- Confirm gender.
- Confirm age is expressed in years.
- Confirm weight is expressed in kg.
- Confirm height is expressed in cm.
- Confirm activity.
- Check the result against your source or provider.
Calculators Percentage Editorial Team
Calculator guides from the Calculators Percentage team. These introductory examples are educational, not professional advice.
Last reviewed:
This is a screening or planning estimate, not a diagnosis. Age, pregnancy, medication and individual medical history can change how the result should be interpreted.