TDEE Formulas | Which Equation to Use and How Each One Works?
Track your daily calorie needs with the TDEE formulas (BMR multiplied by activity factor). Learn how they work, what factors affect them, and how to use them for weight loss or muscle gain.
TDEE formulas are mathematical equations that estimate Total Daily Energy Expenditure, the total number of calories a person burns in a 24-hour period. Every TDEE formula works in two steps. First, it calculates Basal Metabolic Rate (BMR), the calories the body burns at complete rest to sustain all vital functions. Second, it multiplies that BMR by an activity multiplier that accounts for movement, exercise, and food digestion.
Three primary formulas are used to calculate BMR for TDEE estimation, including the Mifflin-St Jeor Equation, the Harris-Benedict Equation, and the Katch-McArdle Equation. Each was developed from a different research population and produces slightly different results. The formula best suited to any individual depends on what biometric data is available and how closely their body composition matches population averages.
Choosing the wrong formula, applying the wrong activity multiplier, or using outdated inputs are the three most common sources of error in TDEE calculation. This article covers each TDEE formula in full, explains how they differ, and shows how to apply them to produce accurate TDEE estimates for fat loss, weight maintenance, and muscle gain. You can run any of these formulas instantly using the TDEE Calculator.
What Is a TDEE Formula and How Does It Work?
A TDEE formula estimates total daily calorie burn by converting physical measurements into a resting energy value (BMR) and then scaling that value upward to reflect real-world activity. The formula does not measure actual calorie expenditure. It produces an estimate based on population-level data from clinical research.
TDEE formulas exist because direct measurement of total energy expenditure requires laboratory methods such as doubly labeled water or metabolic chambers, which are not accessible outside clinical or research settings. Validated equations approximate the results of those methods using inputs that any person can measure at home.
What Inputs Do TDEE Formulas Require?
The inputs required differ slightly between formulas. Most use four standard biometric variables.
Input Variable | Required By | Effect on BMR Output | Effect on TDEE Output |
|---|---|---|---|
Body weight (kg) | All three formulas | Higher weight raises BMR | Higher weight raises TDEE proportionally |
Height (cm) | Mifflin-St Jeor, Harris-Benedict | Taller height raises BMR | Taller height raises TDEE modestly |
Age (years) | Mifflin-St Jeor, Harris-Benedict | Older age lowers BMR | Older age lowers TDEE proportionally |
Biological sex | Mifflin-St Jeor, Harris-Benedict | Male sex raises BMR by 5 to 10% | Male sex raises TDEE proportionally |
Body fat percentage | Katch-McArdle only | Used to derive lean body mass | Used to calculate lean-mass-based TDEE |
Katch-McArdle does not use height, age, or sex. It uses lean body mass exclusively, making it the most accurate formula for individuals whose body composition differs significantly from population averages.
How the Two-Step TDEE Formula Works?
Every TDEE formula follows the same two-step structure regardless of which BMR equation is used.
Step 1: Calculate BMR using weight, height, age, and sex (or lean body mass for Katch-McArdle).
Step 2: Multiply BMR by the activity multiplier that reflects weekly exercise frequency and daily movement pattern.
The result is the TDEE estimate. For a full breakdown of TDEE and all four of its components (BMR, NEAT, EAT, and TEF), visit the TDEE guide. To calculate your BMR directly, use the BMR Calculator.
What Are the Three Main TDEE Formulas?
Three BMR equations are used to calculate TDEE in clinical nutrition, academic research, and consumer-facing calculators. Each has a different history, research basis, and accuracy profile.
TDEE Formula Comparison at a Glance
Formula | Year Published | Research Base | Best For | Known Limitation |
|---|---|---|---|---|
Mifflin-St Jeor | 1990 | 498 adults, measured RMR | General healthy adults | Less accurate at very high or low body fat |
Harris-Benedict (Revised) | 1919, revised 1984 | 239 men and women, revised by Roza and Shizgal | Broad population use | Overestimates BMR by approximately 5% |
Katch-McArdle | 1996 | Lean body mass dataset | Athletes, individuals with measured body fat | Requires accurate body fat measurement |
The Mifflin-St Jeor Equation is the most widely recommended for healthy adults without a known body fat percentage. A 2005 study published in the Journal of the American Dietetic Association compared all major BMR equations against indirect calorimetry measurement and found Mifflin-St Jeor accurate within plus or minus 10% for 82% of subjects tested. Detailed coverage of each individual formula is available at the dedicated pages for Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle.
The Mifflin-St Jeor Equation (The Most Accurate General Formula)
The Mifflin-St Jeor Equation was published in 1990 by Mark D. Mifflin and Sachiko T. St Jeor following a study of 498 healthy adults. It is the default formula in most registered dietitian software, clinical nutrition guidelines, and major online TDEE calculators. The equation replaced the older Harris-Benedict formula as the preferred standard after research demonstrated it more accurately predicted measured resting metabolic rate.
The Mifflin-St Jeor formula uses body weight, height, age, and biological sex as inputs. It applies a fixed sex constant of plus 5 for males and minus 161 for females to the same base calculation.
The Mifflin-St Jeor Formula
For males:
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
For females:
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161
Worked Examples
Example 1 (Male, 32 years old, 82 kg, 180 cm):
BMR = (10 × 82) + (6.25 × 180) - (5 × 32) + 5 BMR = 820 + 1,125 - 160 + 5 = 1,790 calories
Example 2 (Female, 28 years old, 65 kg, 163 cm):
BMR = (10 × 65) + (6.25 × 163) - (5 × 28) - 161 BMR = 650 + 1,018.75 - 140 - 161 = 1,367.75 calories
TDEE Outputs From Mifflin-St Jeor at Different Activity Levels
Using the male BMR of 1,790 calories from Example 1:
Activity Level | Multiplier | TDEE Estimate |
|---|---|---|
Sedentary | 1.2 | 2,148 calories |
Lightly Active | 1.375 | 2,461 calories |
Moderately Active | 1.55 | 2,775 calories |
Very Active | 1.725 | 3,088 calories |
Extra Active | 1.9 | 3,401 calories |
When to Use Mifflin-St Jeor
Mifflin-St Jeor is the correct formula for most adults under the following conditions:
Body fat percentage is unknown or estimated
Body composition is close to the population average (approximately 15 to 25% body fat for males, 22 to 32% for females)
The person is a generally healthy adult aged 18 to 65
No DEXA scan, hydrostatic weighing, or calibrated skinfold measurement is available
The formula becomes less accurate for individuals at the extremes of body composition. For a very lean athlete or a person with high body fat, the Katch-McArdle formula will produce a more accurate BMR and therefore a more accurate TDEE. To get complete knowledge, read this guide on the TDEE Calculator.
The Harris-Benedict Equation (The Original TDEE Formula)
The Harris-Benedict Equation is the oldest of the three main BMR formulas. James Arthur Harris and Francis Gano Benedict published the original version in 1919 following a study of 239 men and women. It was the primary BMR formula used in clinical and research settings for over 60 years. A revised version was published in 1984 by Roza and Shizgal, correcting for systematic overestimation in the original.
The revised Harris-Benedict formula is still in wide use today, particularly in clinical settings that predate the widespread adoption of Mifflin-St Jeor. It uses the same four inputs (weight, height, age, sex) but applies different coefficients that were derived from a different, smaller research population.
The Harris-Benedict Formula (Revised 1984)
For males:
BMR = (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age in years) + 88.362
For females:
BMR = (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age in years) + 447.593
Worked Examples Using Harris-Benedict
Example 1 (Male, 32 years old, 82 kg, 180 cm):
BMR = (13.397 × 82) + (4.799 × 180) - (5.677 × 32) + 88.362 BMR = 1,098.55 + 863.82 - 181.66 + 88.36 = 1,869 calories
Example 2 (Female, 28 years old, 65 kg, 163 cm):
BMR = (9.247 × 65) + (3.098 × 163) - (4.330 × 28) + 447.593 BMR = 601.06 + 504.97 - 121.24 + 447.59 = 1,432.38 calories
Mifflin-St Jeor vs. Harris-Benedict Output Comparison
Using the same inputs (male, 32, 82 kg, 180 cm) to compare the two formulas directly:
Formula | BMR Output | TDEE at 1.55 (Moderately Active) | Difference vs Mifflin |
|---|---|---|---|
Mifflin-St Jeor | 1,790 calories | 2,775 calories | Baseline |
Harris-Benedict (Revised) | 1,869 calories | 2,897 calories | +122 calories |
The Harris-Benedict formula produces a TDEE estimate 122 calories higher for this individual. Over one year, eating at the Harris-Benedict maintenance instead of the Mifflin maintenance would create a surplus of approximately 44,530 calories, equivalent to approximately 5.8 kg of potential fat gain without any subjective sense of overeating.
When to Use Harris-Benedict
Harris-Benedict remains appropriate in specific contexts:
Clinical settings where it is the established tool and consistency with prior records is required
Comparative research that needs to replicate earlier studies using the original formula
Situations where Mifflin-St Jeor is unavailable and manual calculation is needed
For most individuals calculating their own TDEE for nutrition planning, Mifflin-St Jeor is the more accurate choice.
The Katch-McArdle Equation (The Most Accurate Formula for Athletes)
The Katch-McArdle Equation calculates BMR from lean body mass rather than total body weight. It was published by Frank Katch and Victor Katch in 1996. By removing fat mass from the calculation entirely, it accounts for the fact that adipose tissue has a much lower metabolic rate than muscle, organ, and bone tissue. This makes it significantly more accurate for individuals whose body composition differs from the average population profile.
The formula requires only one input beyond lean body mass: the calculation of lean body mass itself, which requires a measured body fat percentage from a reliable assessment method.
The Katch-McArdle Formula
For both sexes:
BMR = 370 + (21.6 × lean body mass in kg)
Lean body mass calculation:
Lean body mass (kg) = total body weight × (1 - body fat percentage expressed as a decimal)
Worked Examples Using Katch-McArdle
Example 1 (82 kg person with 12% body fat):
Lean body mass = 82 × (1 - 0.12) = 82 × 0.88 = 72.16 kg BMR = 370 + (21.6 × 72.16) = 370 + 1,558.66 = 1,929 calories
Example 2 (82 kg person with 30% body fat):
Lean body mass = 82 × (1 - 0.30) = 82 × 0.70 = 57.40 kg BMR = 370 + (21.6 × 57.40) = 370 + 1,239.84 = 1,610 calories
The same total body weight of 82 kg produces a 319-calorie BMR difference solely based on body composition. At a moderately active multiplier of 1.55, this produces a TDEE difference of 494 calories per day. A standard formula using total weight would assign both individuals the same TDEE, which significantly overestimates maintenance for the higher body fat individual and underestimates it for the lean athlete.
Katch-McArdle vs. Mifflin-St Jeor: Body Composition Impact on TDEE
Using the same 82 kg male inputs across different body fat percentages:
Body Fat % | Lean Mass | Katch-McArdle BMR | TDEE at 1.55 | Mifflin BMR (same weight) | TDEE at 1.55 (Mifflin) | Error |
|---|---|---|---|---|---|---|
10% | 73.8 kg | 1,954 cal | 3,029 cal | 1,790 cal | 2,775 cal | Mifflin underestimates by 254 cal |
20% | 65.6 kg | 1,767 cal | 2,739 cal | 1,790 cal | 2,775 cal | Mifflin overestimates by 36 cal |
30% | 57.4 kg | 1,610 cal | 2,496 cal | 1,790 cal | 2,775 cal | Mifflin overestimates by 279 cal |
40% | 49.2 kg | 1,433 cal | 2,221 cal | 1,790 cal | 2,775 cal | Mifflin overestimates by 554 cal |
At 20% body fat (close to the male population average), Mifflin and Katch-McArdle produce nearly identical TDEE estimates. The further body composition deviates from average, the larger the error from using Mifflin on total weight alone.
When to Use Katch-McArdle
Use the Katch-McArdle formula when the following conditions are met:
A measured body fat percentage is available from DEXA scan, hydrostatic weighing, or calibrated skinfold calipers
The individual is an athlete or regular resistance trainer with body fat below 15% (male) or below 22% (female)
The individual has a body fat percentage above 30% and standard formula outputs do not align with observed weight changes
Body recomposition tracking requires accurate lean mass-based calorie targets
Avoid using estimated body fat percentages from bioelectrical impedance scales or visual comparisons as Katch-McArdle inputs. Measurement errors of 3 to 5 percentage points translate into BMR errors of 65 to 108 calories, which then amplify through the TDEE multiplier.
What Are the TDEE Activity Multipliers and How Do They Affect the Formula Output?
Activity multipliers are the second component of every TDEE formula. They convert a resting BMR value into a full TDEE estimate by scaling upward to reflect real-world calorie burn from movement, exercise, and food processing. The multipliers originate from McArdle, Katch, and Katch's Exercise Physiology framework and represent five standardized activity bands.
The multiplier applied to BMR determines the final TDEE output. An error in multiplier selection is amplified by the full BMR value, producing a larger absolute error than any BMR formula inaccuracy alone.
The Five Standard Activity Multipliers
Activity Level | Multiplier | Description | Typical Weekly Profile | Step Count Proxy |
|---|---|---|---|---|
Sedentary | 1.2 | Little or no exercise | Desk job, no gym, minimal walking | Under 5,000 steps/day |
Lightly Active | 1.375 | Light exercise 1 to 3 days per week | Occasional gym sessions, mostly seated work | 5,000 to 7,500 steps/day |
Moderately Active | 1.55 | Moderate exercise 3 to 5 days per week | Regular gym-goer, some active commuting | 7,500 to 10,000 steps/day |
Very Active | 1.725 | Hard exercise 6 to 7 days per week | Daily training, active lifestyle | 10,000 to 14,000 steps/day |
Extra Active | 1.9 | Very hard exercise plus a physical job | Manual labor plus daily training | 14,000+ steps/day |
How Multiplier Selection Affects TDEE at a Fixed BMR?
Using a BMR of 1,790 calories, the table below shows how each multiplier shifts the TDEE output and how a one-level overestimate changes planned deficits.
Correct Multiplier | Correct TDEE | If User Selects One Level Higher | Inflated TDEE | Surplus Created on 500-cal Deficit |
|---|---|---|---|---|
Sedentary (1.2) | 2,148 cal | Lightly Active (1.375) | 2,461 cal | 313-calorie surplus instead of 500-cal deficit |
Lightly Active (1.375) | 2,461 cal | Moderately Active (1.55) | 2,775 cal | Only 186-calorie net deficit instead of 500 |
Moderately Active (1.55) | 2,775 cal | Very Active (1.725) | 3,088 cal | Only 187-calorie net deficit instead of 500 |
Very Active (1.725) | 3,088 cal | Extra Active (1.9) | 3,401 cal | Only 187-calorie net deficit instead of 500 |
A one-level multiplier overestimate consistently reduces a planned 500-calorie fat loss deficit to approximately 180 to 300 calories. At the sedentary level, a one-level overestimate converts the entire deficit into a surplus.
Rules for Choosing the Correct Multiplier
Selecting the right multiplier requires an honest assessment of the full week, not just the days with gym sessions.
Count only planned, structured exercise sessions toward the activity level, as spontaneous walking and daily movement are captured by NEAT, already folded into the multiplier
A person who trains three times per week but sits for 10 or more hours daily is lightly active or moderately active at most
Use daily step count as a cross-check, as under 5,000 steps supports sedentary, 7,500 to 10,000 supports moderately active
When two multiplier levels appear equally valid, choose the lower one and validate with two to three weeks of weight tracking
How Do TDEE Formulas Relate to BMR in Practice?
BMR and TDEE are inseparable in formula-based calorie planning. BMR is the input; TDEE is the output. Every change in BMR, whether from body weight loss, muscle gain, aging, or formula choice, produces a proportional change in TDEE.
For a full comparison of what BMR and TDEE each measure and how they relate to one another, visit the TDEE vs BMR guide. For a detailed technical breakdown of BMR specifically, the BMR Calculator walks through each formula with live inputs.
How BMR Changes Affect TDEE Formula Outputs?
BMR Change Cause | BMR Impact | TDEE Impact at 1.55 Multiplier | Practical Effect |
|---|---|---|---|
Losing 5 kg of body weight | BMR falls by 40 to 60 cal/day | TDEE falls by 62 to 93 cal/day | Deficit narrows, so recalculate TDEE |
Gaining 3 kg of lean muscle | BMR rises by 39 cal/day | TDEE rises by 60 cal/day | Maintenance calories increase |
Aging 10 years (formula effect) | BMR falls by 50 cal | TDEE falls by 77 cal | Long-term maintenance target lowers |
Switching from Mifflin to Harris-Benedict | BMR rises by 60 to 120 cal | TDEE rises by 93 to 186 cal | Risk of unintended surplus |
Switching from total weight to lean mass (Katch-McArdle) | BMR varies by body fat % | TDEE varies up to 500 cal | Most accurate result for athletes |
Because BMR feeds directly into every TDEE formula, recalculating both BMR and TDEE every 3 to 4 kg of weight change or every 4 to 6 weeks during an active diet or training phase is standard practice. Using an outdated TDEE figure from a calculation made at a higher body weight overestimates maintenance, which narrows any planned deficit without any behavioral change.
How to Choose the Right TDEE Formula for Your Goal?
Formula selection depends on three factors: the biometric data available, the individual's body composition profile, and the goal the TDEE estimate will be used for.
Formula Selection Guide by Profile
Profile | Best Formula | Reason |
|---|---|---|
Average adult, no body fat measurement | Mifflin-St Jeor | Most validated for the general population, as it requires only weight, height, age, and sex |
Resistance-trained athlete, body fat measured | Katch-McArdle | Lean mass-based calculation eliminates body fat overestimation error |
An individual with high body fat (30%+), body fat measured | Katch-McArdle | Standard formulas significantly overestimate BMR and TDEE at high body fat |
Clinical setting requiring historical consistency | Harris-Benedict (Revised) | Matches prior records; still valid when consistency matters more than precision |
Person switching from weight loss to maintenance | Mifflin-St Jeor (recalculated at new weight) | Accurate at population-average body fat; easy to recalculate as weight changes |
Natural bodybuilder or physique athlete | Katch-McArdle | Body fat well below population average; total weight-based formulas underestimate BMR |
Step-by-Step Formula Application Process
Follow this sequence when setting a TDEE-based calorie target for any goal.
Measure current body weight, height, and age accurately; weigh first thing in the morning after using the bathroom
If body fat percentage is known from a reliable measurement, use Katch-McArdle. If not, use Mifflin-St Jeor
Calculate BMR using the chosen formula
Select the activity multiplier that matches the average week, using step count as a cross-check where possible
Multiply BMR by the multiplier to get TDEE
Set the calorie target at TDEE (maintenance), TDEE minus 400 to 500 calories (fat loss), or TDEE plus 150 to 300 calories (lean muscle gain)
Track food intake and body weight for two to three weeks to validate the estimate
Adjust by 100 to 150 calories in the appropriate direction if the weight is not moving as expected
The TDEE Calculator runs all three formulas automatically and displays the TDEE output for all five activity levels simultaneously, removing the need for manual calculation.
How Accurate Are TDEE Formulas and What Causes Estimation Errors?
All TDEE formulas produce estimates with an inherent margin of error. The Mifflin-St Jeor Equation is accurate within plus or minus 10% for approximately 82% of healthy adults. The remaining 18% fall outside this range, and for those individuals, formula-based TDEE may differ from true measured expenditure by 150 to 400 calories per day.
Primary Sources of TDEE Formula Error
Error Source | Which Formula It Affects | Estimated Error Magnitude | How to Correct It |
|---|---|---|---|
Atypical body composition | Mifflin-St Jeor, Harris-Benedict | 150 to 550 calories at the TDEE level | Switch to Katch-McArdle with measured body fat |
Incorrect activity multiplier | All formulas equally | 200 to 500 calories at the TDEE level | Reassess weekly training and step count honestly |
Using estimated body fat in Katch-McArdle | Katch-McArdle | 65 to 120 calories at the BMR level | Use measured body fat from DEXA or hydrostatic weighing |
Not recalculating after weight change | All formulas | 60 to 200 calories per 5 kg of weight change | Recalculate every 3 to 4 kg or every 4 to 6 weeks |
Metabolic adaptation during dieting | All formulas | 100 to 300 calories below formula prediction | Take diet breaks and revalidate with weight tracking |
How to Validate Your TDEE Formula Output
The most reliable validation method is two to three weeks of simultaneous food intake tracking and daily body weight monitoring.
Set daily calorie intake exactly to the formula-calculated TDEE
Track all food using a digital food scale and a calorie tracking application
Weigh at the same time each morning under the same conditions
Average weekly body weight and compare across weeks
If the average weight is stable, the formula estimate is accurate. If weight is decreasing, the true TDEE is higher than the formula output. If weight is increasing, true TDEE is lower. Adjust by 100 to 150 calories per day in the appropriate direction and repeat the validation cycle for another two weeks.
Key Takeaways
TDEE formulas calculate total daily energy expenditure in two steps: first BMR, then BMR multiplied by an activity multiplier
The three main BMR formulas used for TDEE are Mifflin-St Jeor (most accurate for general adults), Harris-Benedict Revised (older formula, overestimates by approximately 5%), and Katch-McArdle (most accurate for athletes with measured body fat)
Mifflin-St Jeor is accurate within plus or minus 10% for 82% of healthy adults and is the default recommendation for most people
Katch-McArdle produces TDEE estimates that differ from Mifflin-St Jeor by up to 500 calories per day for individuals with high or low body fat percentages at the same total weight
Activity multipliers range from 1.2 (sedentary) to 1.9 (extra active); a one-level overestimate reduces a planned 500-calorie fat loss deficit to approximately 180 to 300 calories
Harris-Benedict overestimates BMR by approximately 5% compared to measured values; Mifflin-St Jeor is a more accurate replacement for most individuals
Every change in BMR from weight loss, muscle gain, or aging produces a proportional change in TDEE through the activity multiplier
TDEE formula outputs should be validated with two to three weeks of intake and weight tracking before being treated as a confirmed maintenance number
Recalculate BMR and TDEE every 3 to 4 kg of weight change or every 4 to 6 weeks during any active diet or training phase
Use the TDEE Calculator to run all three formulas instantly, or the BMR Calculator to compare BMR outputs side by side