Calorie Needs (TDEE) Calculator

This calculator estimates your Total Daily Energy Expenditure (TDEE) — the number of calories your body burns in a typical day, including everything from basic organ function to workouts and daily movement. It then adjusts that number for your goal, giving you a practical calorie target for maintaining, losing, or gaining weight.

What is TDEE and why does it matter?

Your TDEE is made up of your Basal Metabolic Rate (BMR — the energy your body needs at complete rest) plus the additional calories burned through daily activity and exercise. Knowing a reasonable estimate of your TDEE is the starting point for almost any nutrition goal: eat around it to maintain weight, below it to lose weight, or above it to gain weight. Guessing at this number is one of the most common reasons diets stall or plateau unexpectedly.

How this calculator works

This tool estimates your BMR using the Mifflin-St Jeor equation, which is generally considered more accurate for most modern adults than older formulas like Harris-Benedict. It then multiplies that BMR by an activity factor based on your selected activity level to estimate maintenance calories, and finally adjusts that number based on your goal:

• Sex, age, weight, and height all feed directly into the BMR formula, since metabolic rate depends on body size, composition, and biological sex.
• Activity level is applied as a multiplier to BMR, scaling from 1.2 (sedentary) up to 1.9 (extremely active).
• Goal shifts the final number up or down using a calorie adjustment based on roughly 7,700 kcal per kilogram of body fat, spread across a week.

The result is shown as a range rather than one exact number, since even validated formulas like Mifflin-St Jeor typically estimate BMR within about 10% of measured values for a given individual — a range is a more honest representation of that uncertainty than a single falsely precise digit.

Calorie needs by activity level

Activity level has one of the largest effects on daily calorie needs, often more than body weight alone:

• Sedentary (little or no exercise): BMR × 1.2
• Lightly active (light exercise 1–3 days/week): BMR × 1.375
• Moderately active (moderate exercise 3–5 days/week): BMR × 1.55
• Very active (hard exercise 6–7 days/week): BMR × 1.725
• Extremely active (very hard training or a physically demanding job): BMR × 1.9

Calories for weight loss

A calorie deficit — eating less than you burn — is what drives fat loss, regardless of any individual food's specific properties. This calculator uses a moderate approach: a "mild" deficit targets about 0.25 kg (roughly 0.5 lb) of loss per week, while a standard deficit targets about 0.5 kg (roughly 1 lb) per week. Larger deficits can work but tend to be harder to sustain and are more likely to cost muscle mass alongside fat, especially without adequate protein intake and resistance training.

Calories for muscle gain

Building muscle generally requires a calorie surplus to support new tissue growth, though the amount of muscle actually gained depends heavily on training and protein intake, not just extra calories. A conservative surplus (mild gain) tends to add less fat alongside muscle compared to a larger surplus, which is why this calculator offers both a mild and a standard muscle-gain option.

Why we show a range, not one exact number

No BMR equation, including Mifflin-St Jeor, can perfectly predict any one individual's metabolism — body composition, genetics, and other factors all cause real variation. Treat the calculated range as a starting point: track your actual weight over two to three weeks at a given calorie intake, and adjust from there based on what really happens, rather than assuming the calculator's number is exact on day one.

Frequently asked questions

What's the difference between BMR and TDEE?

BMR is the energy your body needs at complete rest, just to keep basic functions running. TDEE adds in the calories burned through daily movement, exercise, and general activity, making it the more useful number for setting an actual calorie target.

Why do I need to enter my age and sex?

The Mifflin-St Jeor equation used here calculates BMR differently based on sex (due to average differences in body composition) and reduces the estimate slightly with age (reflecting typical age-related changes in metabolic rate).

How accurate is this calculator?

Mifflin-St Jeor is one of the better-validated BMR equations for the general population, typically estimating BMR within about 10% of directly measured values. Real-world TDEE also depends on activity you may not perfectly categorize, so treat the result as a solid starting estimate to adjust from, not a lab measurement.

Should I eat exactly the number this calculator gives me?

It's a reasonable starting point, but the most reliable approach is to eat at the estimated target for two to three weeks, track your actual weight trend, and adjust up or down based on what you observe.

Why is my "mild" goal only a 275-calorie adjustment?

It's based on roughly 7,700 kcal stored per kilogram of body fat, spread across seven days for a 0.25 kg/week rate of change — a pace that's easier to sustain and less likely to cost lean muscle than a more aggressive deficit or surplus.

Medical disclaimer

Sources & references

• Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." The American Journal of Clinical Nutrition, 1990. pubmed.ncbi.nlm.nih.gov/2305711
• Frankenfield D, et al. "Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults." Journal of the American Dietetic Association, 2005. pubmed.ncbi.nlm.nih.gov/15883556
• U.S. Department of Agriculture & Department of Health and Human Services. Dietary Guidelines for Americans. dietaryguidelines.gov
• Academy of Nutrition and Dietetics. eatright.org