About the calorie calculator
This calorie calculator estimates how much energy you use each day and what a daily calorie target might look like for maintaining, losing or gaining weight. It builds on your basal metabolic rate and multiplies it by an activity level.
It then shows what daily adjustment corresponds to your chosen weekly change, and it warns you when that target is lower than commonly advised minimums.
Who should use the calorie calculator
- Adults planning weight maintenance, gradual loss or gradual gain.
- People who want to understand how activity level changes daily energy needs.
- Anyone preparing questions for a dietitian.
How to use the calorie calculator: what each input means
- Sex, age, height, weight
- Used to estimate BMR with the Mifflin-St Jeor equation (or Katch-McArdle if you provide body fat).
- Activity level
- From sedentary to extra active. Choose the level that matches a typical week, not your best week.
- Goal
- Maintain, lose or gain a chosen amount per week.
- Energy unit
- Calories (kcal) or kilojoules (kJ).
How the calorie calculator works: method and formula
Maintenance calories (often called TDEE, total daily energy expenditure) are BMR multiplied by an activity factor: 1.2 for sedentary, 1.375 for light, 1.465 for moderate, 1.55 for active, 1.725 for very active and 1.9 for extra active. These are widely used approximations, not measured values.
For weight change the calculator assumes roughly 7,700 kcal of energy is equivalent to 1 kg of body weight (about 3,500 kcal per pound). That is a simplification: in practice metabolism adapts and the rate of change slows.
- Maintenance
- TDEE = BMR × activity factor
- Target
- Target = TDEE + (kg per week × 7,700) ÷ 7
How to read your calorie calculator result
Use the maintenance figure as a starting point and watch your weight for two to three weeks. If it is stable, the estimate is about right for you; if not, adjust gradually. Large daily deficits are not recommended without supervision, which is why very low targets trigger a warning.
Weight changes come from more than calories: water, hormones and muscle all play a role, so short-term movement on the scale is normal.
Calorie Calculator worked example
A 30-year-old woman, 175 cm and 70 kg, with a light activity level who wants to maintain her weight.
- BMR (Mifflin-St Jeor) = 1,482.8 kcal/day.
- Maintenance = BMR × 1.375 = 2,039 kcal/day.
- For a 0.5 kg-a-week loss: 0.5 × 7,700 ÷ 7 = 550 kcal/day less, giving a target of about 1,489 kcal/day.
About 2,039 kcal per day to maintain weight.
Practical uses of the calorie calculator
- Getting a first estimate before a structured plan.
- Seeing how a more active routine changes your needs.
- Comparing a gentle and a faster rate of change.
Assumptions and limitations of this calculator
- Estimates only. Actual needs depend on body composition, medical conditions, medication, sleep, stress and how accurately you judge your activity.
- The 7,700 kcal per kg rule is a rough average and overstates how fast weight changes as you lose or gain over time.
- Not suitable for children, pregnancy or breastfeeding, eating disorders or medical diets. Do not use it to set an extreme deficit.
This calculator is for general information and education only. It is not medical advice, a diagnosis or a treatment plan. Results are estimates based on population formulas and cannot account for your individual health. If you have a medical condition, are pregnant, are under 18, or are planning a major change to your diet or exercise, speak to a doctor or registered dietitian first.