What Is a Calorie Calculator?
A calorie calculator estimates how many calories you need each day to maintain, lose, or gain weight, based on your age, sex, height, weight, and activity level. It starts from your Basal Metabolic Rate (BMR) and adjusts for how active you are.
How to Use the Calorie Calculator
- Select your sex and enter your age.
- Enter your current weight and height.
- Choose the activity level that best matches your typical week.
- Review your maintenance calories and targets for weight loss or gain.
Calorie Calculation Formula
BMR is calculated using the Mifflin-St Jeor equation: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 for men, or −161 for women.
Worked Example
BMR ≈ 1,660 calories/day
Activity multiplier: 1.55 (moderate exercise)
Maintenance calories ≈ 2,573 calories/day
To lose about 1 lb/week: eat roughly 2,073 calories/day.
Understanding Your Results
Maintenance Calories is the amount you'd need to eat to keep your weight stable. A pound of body fat represents roughly 3,500 calories, so a consistent daily deficit or surplus of about 500 calories translates to roughly 1 lb of change per week.
Tips for Using Your Calorie Target
- Use these numbers as a starting point, then adjust based on how your actual weight trends over 2–3 weeks.
- Very aggressive deficits (over 1,000 calories/day below maintenance) are generally harder to sustain and can affect energy and muscle mass.
- Prioritize protein intake when in a calorie deficit to help preserve muscle mass.
Common Mistakes to Avoid
- Underestimating portion sizes, which quietly increases actual calorie intake above a target.
- Not adjusting the calorie target as weight changes significantly over time.
- Setting an unrealistic deficit that's hard to maintain, leading to inconsistency rather than steady progress.
Frequently Asked Questions
A common approach is eating around 500 calories below your maintenance level for a target of about 1 lb of weight loss per week, though individual needs vary.
Maintenance calories are the number of calories you need daily to keep your current weight stable, accounting for your BMR and activity level.
They provide a solid estimate based on population averages, but individual metabolism varies — many people find they need to adjust their target up or down slightly based on real-world results.
Very low-calorie diets should generally be supervised by a healthcare provider, since they can affect energy levels, muscle mass, and long-term metabolic health.
Yes — the activity multiplier in this calculator already accounts for your typical exercise level. If your activity level changes significantly, recalculate your target.
Roughly 3,500 calories, which is the basis for the commonly used estimate that a 500-calorie daily deficit leads to about 1 lb of fat loss per week.