Calorie Calculator

How many calories should you eat a day? This calorie calculator estimates the calories your body burns from your age, sex, height, weight and activity level, then shows how many to eat to maintain your weight, lose weight or gain weight at a steady pace. It works in pounds and feet or in metric units.

How the Calorie Calculator Works

First it estimates your basal metabolic rate (BMR) – the energy your body uses at complete rest for breathing, circulation and keeping warm – with the Mifflin-St Jeor equation, which research has found to be the most accurate of the common formulas for most adults:

• Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
• Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161

BMR is then multiplied by an activity factor – from 1.2 for a desk job with no exercise up to 1.9 for very hard training or physical work – to give your total daily energy expenditure (TDEE), the calories you need to stay at the same weight.

Example: a 35-year-old man who is 5'9" (175 cm) and 170 lb (77.1 kg) has a BMR of about 1,696 calories. If he exercises lightly 1–3 days a week (× 1.375), he needs about 2,333 calories a day to maintain his weight, about 1,833 to lose 1 lb a week and about 2,583 to gain half a pound a week.

How Many Calories to Lose Weight

A pound of body fat stores roughly 3,500 calories. Eating about 500 calories a day less than your maintenance level leads to about 1 pound of weight loss a week; 250 calories less, to about half a pound. The calculator shows these targets for you. The CDC notes that people who lose weight gradually, at 1 to 2 pounds a week, are more successful at keeping it off.

• Weight loss slows over time, because a smaller body burns fewer calories. Recalculate after every 10 to 15 pounds.
• Women generally shouldn't eat fewer than about 1,200 calories a day and men fewer than about 1,500 without medical supervision – it is hard to get enough nutrients below that.
• Protein-rich foods, vegetables and fiber help you feel full on fewer calories.

Typical Daily Calorie Needs

The Dietary Guidelines for Americans give these estimated needs for adults, depending on activity:

Your personal number can be quite different from these averages, which is why a calculation based on your own height, weight and activity is more useful.

Choosing the Right Activity Level

Most people overestimate how active they are. If you work at a desk and exercise three times a week, Light is usually more accurate than Moderate. A practical approach: start with the calculated number, track your weight for two to three weeks and adjust by 100 to 200 calories if your weight moves differently from what you expect.

Limits of Calorie Calculators

Every formula is an estimate based on averages. Muscle mass, genetics, medications, sleep and hormones all affect how many calories you burn, and individual results can differ by 10% or more. Calorie needs are also different during pregnancy and breastfeeding and for teenagers. If you have a medical condition or want to lose a large amount of weight, talk to your doctor or a registered dietitian.

For a detailed breakdown by activity level and a macro split for cutting or bulking, use the TDEE calculator.

Sources

• Dietary Guidelines for Americans, 2020–2025 – Estimated calorie needs (Appendix 2)
• CDC – Losing weight
• Mifflin MD, St Jeor ST et al. A new predictive equation for resting energy expenditure. Am J Clin Nutr, 1990
• NIH – Body Weight Planner

Last reviewed: October 2026 by the ShrinkBee team. Results are estimates for healthy adults and are not medical advice.

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