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TDEE Calculator: Estimate Your Daily Calories & Maintenance Needs

Estimate your Total Daily Energy Expenditure (TDEE), BMR, and maintenance calories using the Mifflin–St Jeor formula, with an optional Katch–McArdle body-fat comparison. All calculations run in your browser — free, private, and no signup required.

For adults age 18+. This calculator provides general educational information, not individualized nutrition or medical advice.

What Is TDEE?

Total Daily Energy Expenditure (TDEE) is an estimate of the total calories a person uses during a typical day, including resting energy needs and activity. It combines resting energy needs (BMR), everyday movement and non-exercise activity (NEAT), structured exercise, and the thermic effect of food (TEF) into one overall figure.

This calculator uses the Mifflin–St Jeor equation for BMR and applies a standard activity multiplier. The activity-factor model already incorporates the thermic effect of food as part of the overall population estimate, so no separate fixed TEF adjustment is added.

TDEE vs. BMR vs. Maintenance Calories

BMR estimates resting energy needs, while TDEE estimates total daily energy expenditure after activity is included. Estimated TDEE is commonly used as a starting estimate for maintenance calories. Understanding the difference helps you use a TDEE calculator more effectively.

In this calculator, estimated TDEE serves as the starting estimate for maintenance calories. Your actual maintenance can only be confirmed over time by tracking body-weight trends alongside reasonably consistent intake and activity.

Mifflin–St Jeor vs. Katch–McArdle

This calculator uses Mifflin–St Jeor as the primary formula and optionally shows a Katch–McArdle comparison when you enter a body-fat percentage.

Different formulas make different assumptions. Showing both is more transparent than combining them into a number that appears more precise than the underlying data supports. That is why this calculator does not average them automatically.

How to Choose the Right TDEE Activity Level

Activity level is one of the largest sources of uncertainty in a TDEE estimate. The five standard levels account for total daily movement — not just workouts.

Don't Count Only Your Workouts

Someone with a desk job who exercises several times per week may have different total daily movement from someone who stands or walks all day at work. Job activity, daily walking, household movement, and structured exercise all contribute. Common mistake: choosing an activity level based only on workouts. This can overestimate or underestimate true daily expenditure.

If You're Between Two Levels

When you are unsure, look at the activity-level comparison table in your calculator results. It shows exactly how much each choice changes your estimated TDEE. There is no single medically correct level — the goal is to pick the one that best describes your typical week.

Why Do TDEE Calculators Give Different Results?

Different TDEE calculators can produce different results because they may use different resting-energy equations, activity factors, body-fat assumptions, and rounding methods. Some calculators use Mifflin–St Jeor, others use Harris–Benedict, and some silently switch or average formulas without telling you. This calculator shows both Mifflin–St Jeor and an optional Katch–McArdle comparison so you can see the difference transparently.

How to Check Whether Your TDEE Estimate Fits Real Life

The most useful way to treat a TDEE calculation is as a starting estimate rather than an exact calorie prescription. A person's actual maintenance can only be assessed over time by tracking reasonably consistent food intake and activity alongside your body-weight trend — rather than reacting to a single day's weight. A multi-week trend is more informative than day-to-day fluctuations. The NIDDK Body Weight Planner is a useful additional resource for exploring how intake and activity interact with body weight over time.

This calculator does not determine your exact maintenance. It provides a planning reference that you can refine with real-world observation.

Why Your TDEE Can Change Over Time

TDEE is not a fixed number. It can shift with changes in body weight, body composition, age, training volume, daily walking or movement, occupation, and recovery. If any of these change meaningfully, recalculating is more useful than relying on an old estimate. Hydration and sleep also influence how you feel and perform during daily activity — you may find our Water Intake Calculator and Sleep Calculator useful companions when building consistent daily routines.

Worked Formula Example

Here is a simple educational example using the Mifflin–St Jeor formula:

This is an example, not a recommended calorie intake for every person.

Evidence Behind This Calculator

Primary Resting-Energy Equation

Mifflin–St Jeor is the primary equation used for this calculator's main BMR estimate. It was developed from measured resting energy expenditure and is widely used as a general predictive equation for healthy adults.

Original Study

The Mifflin–St Jeor equation was published in 1990 in the American Journal of Clinical Nutrition by Mifflin et al. The study measured resting energy expenditure using indirect calorimetry in 498 healthy participants — 247 women and 251 men, ages 19–78 — including 264 normal-weight participants and 234 participants with obesity. The study did not measure any individual user's metabolism, and it does not prove the equation is exact for every person.

Mifflin et al. resting-energy study (PMID 2305711) · DOI: 10.1093/ajcn/51.2.241

Independent Validation Context

Later research has compared common resting metabolic rate equations and found Mifflin–St Jeor to perform well as a general predictive equation. A systematic review by Frankenfield et al. evaluated predictive equations for resting metabolic rate in healthy nonobese and obese adults, providing independent context for why Mifflin–St Jeor is commonly selected as a default equation. This should not be overstated as universal superiority for every person or population.

Frankenfield et al. systematic review of RMR equations (PMID 15883556)

Optional Body-Fat Comparison

Katch–McArdle uses estimated lean body mass rather than age, sex, height, and total body weight in the same way as Mifflin–St Jeor. The formula implemented in this calculator is:

RMR = 370 + (21.6 × lean body mass in kg)

It is optional, shown as a comparison only, and the primary result always uses Mifflin–St Jeor. The accuracy of the Katch–McArdle estimate depends significantly on the quality of the body-fat percentage entered.

Katch–McArdle formula documentation (PMCID PMC12425712)

Activity Factors Are Separate From the Mifflin Equation

The activity multipliers are not part of the original 1990 Mifflin–St Jeor equation. The calculator first estimates resting energy needs with Mifflin–St Jeor and then applies a commonly used activity factor to estimate total daily energy expenditure. The factors used in this calculator — ×1.20, ×1.375, ×1.55, ×1.725, and ×1.90 — are also used in published research, but they should not be described as scientifically proven universal multipliers.

Published study using these activity factors (PMCID PMC11679847)

Calculator at a Glance

What This Calculator Cannot Know

A predictive equation cannot directly measure your actual resting metabolic rate, exact daily movement, individual thermic effect of food, changes in energy expenditure from day to day, metabolic adaptations, exact body composition unless measured separately, or medical and physiological factors not included in the inputs.

Indirect calorimetry or other direct measurement methods can provide information that a predictive equation cannot. This calculator is a practical planning tool, not a replacement for direct measurement or individualized professional guidance.

Methodology & Sources

This calculator uses the Mifflin–St Jeor equation, published in a 1990 study comparing predictive resting-energy equations. Activity multipliers are commonly used factors applied after the resting-energy estimate; they are not part of the original Mifflin–St Jeor equation. The optional Katch–McArdle formula uses lean body mass derived from self-reported body-fat percentage.

• Mifflin et al. resting-energy study (PMID 2305711)
• Frankenfield et al. systematic review of RMR equations (PMID 15883556)
• Katch–McArdle formula documentation (PMCID PMC12425712)
• Published study using these activity factors (PMCID PMC11679847)
• NIDDK Body Weight Planner

Wellness Vital Tips does not employ a medical reviewer. No medical, dietitian, or clinical credentials are claimed. This page is educational and is not a substitute for professional nutrition or medical guidance.

Last updated: August 2026

Frequently Asked Questions About TDEE

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