What Is the Harris-Benedict Equation?

The Harris-Benedict equations estimate basal metabolic rate (BMR) — calories your body uses at complete rest — from weight, height, age, and sex. James Arthur Harris and Francis Gano Benedict published the original formulas in 1919 after indirect calorimetry studies at the Carnegie Institution. They remain among the most cited BMR equations in nutrition textbooks and software, though modern comparisons often favor updated coefficients (1984 revision) or Mifflin-St Jeor (1990) for general adult populations.

BMR vs RMR vs TDEE

Metric

BMR

What it measures

Resting energy under strict fasting, rest conditions

Best use

Baseline metabolism; Harris-Benedict estimates this

Metric

RMR

What it measures

Resting energy, less strict lab protocol

Best use

Often slightly higher than BMR in practice

Metric

TDEE

What it measures

Total daily energy (BMR × activity factor)

Best use

Maintenance and goal calorie planning

Harris-Benedict Formulas Explained

Revised Harris-Benedict (1984) — recommended

Male:
BMR = 88.362 + (13.397 × kg)
    + (4.799 × cm) − (5.677 × age)

Female:
BMR = 447.593 + (9.247 × kg)
    + (3.098 × cm) − (4.330 × age)
kg
Body weight in kilograms
cm
Height in centimeters
age
Age in years

Original Harris-Benedict (1919)

Male:
BMR = 66.47 + (13.75 × kg)
    + (5.003 × cm) − (6.755 × age)

Female:
BMR = 655.1 + (9.563 × kg)
    + (1.850 × cm) − (4.676 × age)
kg
Body weight in kilograms
cm
Height in centimeters
age
Age in years

Every variable is required. Weight and height increase estimated resting energy; age subtracts from the total; sex-specific constants reflect population-average differences in body composition.

Worked Examples

Adult male — Revised (1984): 30 years, 175 cm, 70 kg

Standard revised Harris-Benedict.

  1. BMR = 88.362 + (13.397 × 70) + (4.799 × 175) − (5.677 × 30)
  2. BMR = 88.362 + 937.79 + 839.83 − 170.31 ≈ 1,696 kcal/day

Result: Estimated BMR ≈ 1,696 kcal/day (revised)

Adult female — Original (1919): 30 years, 165 cm, 60 kg

Original coefficients for comparison.

  1. BMR = 655.1 + (9.563 × 60) + (1.850 × 165) − (4.676 × 30)
  2. BMR = 655.1 + 573.78 + 305.25 − 140.28 ≈ 1,394 kcal/day

Result: Estimated BMR ≈ 1,394 kcal/day (original)

Original vs Revised Harris-Benedict

Aspect

Year / source

Original (1919)

Harris & Benedict, Carnegie Institution

Revised (1984)

Roza & Shizgal, Am J Clin Nutr

Aspect

Typical bias vs modern RMR

Original (1919)

Often overestimates for many adults today

Revised (1984)

Closer to measured values; still a population estimate

Aspect

Best use

Original (1919)

Historical comparison, education

Revised (1984)

Default for Harris-Benedict planning

Aspect

Accuracy note

Original (1919)

Superseded for most clinical/nutrition use

Revised (1984)

Mifflin-St Jeor may still outperform in meta-analyses

How Activity Level Affects Calorie Needs

Level

Sedentary

Multiplier

1.2

Example profile

Desk job, minimal walking

Level

Lightly Active

Multiplier

1.375

Example profile

Office worker who walks daily

Level

Moderately Active

Multiplier

1.55

Example profile

Student with regular gym sessions

Level

Very Active

Multiplier

1.725

Example profile

Construction worker or daily hard training

Level

Extra Active

Multiplier

1.9

Example profile

Athlete or manual labor plus training

TDEE = BMR × activity factor. These multipliers approximate daily movement, NEAT, and typical thermic effect of food in one step — not a measured value. Use the Activity Level Quiz if unsure.

Factors That Affect BMR

Harris-Benedict captures weight, height, age, and sex — the strongest predictors available without body-composition data. Individual BMR also shifts with muscle mass, genetics, hormones, sleep, stress, illness, medications, pregnancy, and climate. Equations cannot model all of this; that is why trend-based calibration matters.

Harris-Benedict vs Mifflin-St Jeor

Aspect

Year

Harris-Benedict (revised)

1984 revision of 1919 work

Mifflin-St Jeor

1990

Aspect

Research support today

Harris-Benedict (revised)

Classic reference; often slightly higher estimates

Mifflin-St Jeor

Frequently recommended default in meta-analyses

Aspect

Frankenfield validation (±10% of measured RMR)

Harris-Benedict (revised)

~67% of adults (2003 cohort; revised equation)

Mifflin-St Jeor

~78% of adults (2003 cohort); ~82% non-obese / ~70% obese (2005 review)

Aspect

Best use

Harris-Benedict (revised)

Historical context, cross-check, education

Mifflin-St Jeor

General adult default without body-fat data

Harris-Benedict vs Katch-McArdle

Katch-McArdle (lean-body-mass based)

Lean mass (kg) = weight (kg)
    × (1 − body fat % / 100)

BMR = 370 + (21.6 × lean mass kg)
kg
Body weight in kilograms
BF%
Body fat percentage (required)

Use Harris-Benedict when you have standard anthropometrics only. Consider Katch-McArdle when you have a reliable body fat percentage (DEXA, hydrostatic weighing) — especially for lean or muscular individuals. Guessed body fat can make Katch less accurate than Harris or Mifflin. Use the Katch-McArdle Calculator when you have a solid body fat estimate, or the Cunningham RMR Calculator when you have direct lean-mass data. For children, teens, and WHO age-band BMR from weight alone, see the Schofield Calculator. For adult weight-only RMR without height, try the Owen Calculator. Compare all seven resting-energy equations in the REE Calculator or RMR Calculator.

How Accurate Is the Harris-Benedict Equation?

Expect roughly ±10–15% individual variation around any population equation. Frankenfield et al. (2005) found Mifflin-St Jeor matched measured RMR within ~10% for more adults than Harris-Benedict in pooled validation data. In one direct validation study (Frankenfield et al., 2003), the standard Harris-Benedict equation was within ±10% for about 67% of subjects versus about 78% for Mifflin-St Jeor. The original 1919 equation often overestimates compared with modern indirect calorimetry. Treat your result as a starting estimate — verify with 2–3 weeks of consistent intake and weight trend.

TDEE estimate error comes from two stacked layers — and the second is usually bigger in practice.

Layer 1: BMR formula error

Mifflin-St Jeor predicts resting metabolic rate within ~10% for roughly 82% of non-obese adults and ~70% of obese adults (Frankenfield et al., 2005). That is ±150–200 kcal for many people.

Layer 2: Activity multiplier error

Picking one activity bucket too high adds ~200–400 kcal/day. Most people remember gym time but underestimate desk hours. Take our Activity Level Quiz if unsure.

Evidence-Based Metabolism Tips

Resting metabolic rate is influenced by muscle mass, protein intake, sleep, physical activity, and recovery — but no single habit dramatically “fixes” a formula estimate overnight. Resistance training helps preserve lean mass during deficits; adequate protein supports satiety and muscle retention; consistent sleep supports appetite regulation. Use your TDEE or goal calories as a journaling anchor, not a rigid prescription.

Common Mistakes

Mistake

Using Original (1919) for modern planning

Better approach

Default to Revised (1984); compare variants intentionally

Mistake

Picking too high an activity level

Better approach

Use conservative level or Activity Quiz; adjust from trends

Mistake

Eating at BMR instead of TDEE

Better approach

Plan at TDEE or goal-adjusted TDEE for full-day targets

Mistake

Never recalculating after weight change

Better approach

Recalculate after ~5–10 kg change or major activity shift

Common Myths vs Facts

Myth

Harris-Benedict is always the most accurate BMR formula.

Evidence-based view

It is classic and useful, but Mifflin-St Jeor often matches measured RMR better in modern comparisons.

Myth

Eating below BMR stops fat loss permanently.

Evidence-based view

Weight change follows energy balance over time; very low intakes may not suit everyone and require professional guidance.

Myth

Original and revised Harris-Benedict give the same answer.

Evidence-based view

Coefficients differ; revised usually yields lower estimates than original for the same inputs.

Interpretation Guide

How to Interpret Your Results

From Harris-Benedict BMR to actionable planning numbers.

Output

BMR

Meaning

Resting energy estimate

Next step

Multiply by activity for TDEE

Output

TDEE

Meaning

Maintenance at selected activity

Next step

Use for maintain or adjust for goals

Output

Goal calories

Meaning

TDEE adjusted for deficit/surplus

Next step

Hand off to macro or deficit tools

Output

BMI band

Meaning

Weight-for-height context

Next step

Informational only — not a prescription

Suggested next steps

BEE Calculator

Classic Harris-Benedict BEE + seven-equation hub

Fat-Free Mass Calculator

FFM from measured or estimated body fat %

Lean Body Mass Calculator

Anthropometric LBM when BF% unknown

Mifflin-St Jeor Calculator

Compare with the modern default BMR equation

Macro Calculator

Split goal calories into protein, fat, and carbs

Calorie Deficit Calculator

Plan structured deficits with safety guardrails

Calorie Surplus Calculator

Bulking presets and lean bulk guidance

Full TDEE Calculator

Homepage calculator with formula choice and macros

Frequently Asked Questions

Common questions about the harris-benedict calculator.

What is the Harris-Benedict equation?
A pair of formulas (1919 original and 1984 revised) that estimate basal metabolic rate from weight, height, age, and sex. They are among the oldest and most cited BMR prediction equations in nutrition.
What is the Harris-Benedict formula for men (revised)?
BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age). This 1984 revision is the recommended default on this calculator.
What is the Harris-Benedict formula for women (revised)?
BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age).
What is the original Harris-Benedict (1919) formula?
Men: BMR = 66.47 + (13.75 × kg) + (5.003 × cm) − (6.755 × age). Women: BMR = 655.1 + (9.563 × kg) + (1.850 × cm) − (4.676 × age). Shown for historical comparison.
Should I use original or revised Harris-Benedict?
Use Revised (1984) for modern calorie planning. Original (1919) often overestimates compared with current indirect calorimetry data — useful mainly for education and comparison.
Is Harris-Benedict accurate?
It is a population estimate with typical ±10–15% individual error. Frankenfield et al. (2003) found the standard Harris-Benedict equation within ±10% of measured RMR for about 67% of adults versus about 78% for Mifflin-St Jeor; the 2005 review also ranked Mifflin-St Jeor as more reliable overall. Calibrate from weight trends.
Is Harris-Benedict better than Mifflin-St Jeor?
For most adults without body-fat data, Mifflin-St Jeor is often the better default in meta-analyses. Harris-Benedict remains valuable as a classic reference and cross-check.
What is the difference between BMR and TDEE?
BMR is resting energy only. TDEE ≈ BMR × activity factor (1.2–1.9), approximating total daily use including movement and typical thermic effect of food.
What are maintenance calories?
Estimated TDEE at your selected activity level — calories that may keep weight stable for many adults. Verify with 2–3 weeks of consistent intake and weight trend.
Can athletes use Harris-Benedict?
Yes as a starting estimate, but very active or muscular individuals may see larger errors. Consider Katch-McArdle with reliable body fat % and trend-based calibration.
Should I eat at my BMR?
Usually no. Most people need TDEE or goal-adjusted TDEE because daily activity adds substantial energy beyond resting metabolism.
How do activity multipliers work?
Sedentary (1.2) through Extra Active (1.9) scale BMR to TDEE. Pick the level matching an average week, not your best day.
What are goal calories in the results?
TDEE adjusted by goal: maintain (100%), weight loss tiers (−10/−15/−20%), lean gain (+5%), weight gain (+10%). For journaling only — not medical advice.
How often should I recalculate?
Every 4–6 weeks, or after ~5–10 kg (10–15 lb) weight change, or when job or training activity shifts meaningfully.
Is Harris-Benedict suitable for weight loss?
It estimates BMR/TDEE — a starting point. Apply a deficit below maintenance (see goal options or Deficit Calculator) and adjust from real-world weight change.
Does Harris-Benedict work for older adults?
It includes an age term but was not designed specifically for older populations. Errors can be larger — prioritize trend-based verification.
Does Harris-Benedict work during pregnancy?
No. Pregnancy increases energy needs beyond standard BMR equations. This tool is not intended for pregnancy planning.
Why is my original BMR higher than revised?
1919 coefficients were derived from early 20th-century data and typically produce higher estimates than the 1984 revision for the same inputs.
When should I use Katch-McArdle instead?
When you have reliable body fat percentage — especially if lean or muscular. Enter body fat in Advanced options to see a Katch cross-check.
What is the BMI card?
Body mass index with WHO adult categories and a healthy weight band for your height — informational context only.
What is the variable breakdown?
Shows how each Harris-Benedict term (weight, height, age, base constant) contributes to your BMR sum — educational, not a separate measurement.
What is the ±10% BMR range?
A practical band reflecting typical population-equation error — not a guarantee your true metabolism lies within it.
How is this different from the BMR Calculator?
This page focuses on Harris-Benedict with original/revised toggle, TDEE table, goal calories, and deep equation education. The BMR Calculator lets you pick any formula as primary.
Can I get macros from these results?
Use the Macro Calculator link in results — it pre-fills your selected goal calories for protein, fat, and carb gram targets.
Does this store my data?
Inputs may save to local storage on this device for convenience. Nothing is sent to a server.
Is this medical advice?
No. Informational tool for personal awareness and nutrition journaling only.
Who created the Harris-Benedict equation?
James Arthur Harris and Francis Gano Benedict at the Carnegie Institution of Washington, published in 1919; revised coefficients by Roza & Shizgal in 1984.

Research & References

Each citation below supports a specific claim on this page. We explain relevance so you can verify the science yourself.

  1. National Academies of Sciences, Engineering, and Medicine — Factors Affecting Energy Expenditure and Requirements. Dietary Reference Intakes for Energy — NCBI Bookshelf, 2023.Defines TDEE components (REE, TEF, PAEE) and explains why population equations cannot capture individual metabolic variation.
  2. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO — A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247, 1990.Primary source for the Mifflin-St Jeor BMR equation used as the default in this calculator.
  3. Roza AM, Shizgal HM — The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168-182, 1984.Source for the revised Harris-Benedict coefficients — default equation on this calculator page.
  4. McArdle WD, Katch FI, Katch VL — Exercise Physiology: Energy, Nutrition, and Human Performance. Lippincott Williams & Wilkins, 7th edition, 2010.Textbook reference for the lean-body-mass-based Katch-McArdle resting energy estimate.
  5. Frankenfield D, Roth-Yousey L, Compher C — Comparison of Predictive Equations for Resting Metabolic Rate in Healthy Nonobese and Obese Adults. J Am Diet Assoc. 2005;105(5):775-789, 2005.Meta-analysis showing Mifflin-St Jeor within ~10% of measured RMR for ~82% of non-obese and ~70% of obese adults — supports honest accuracy framing.
  6. Frankenfield DC, Rowe WA, Smith JS, Cooney RN — Validation of several established equations for resting metabolic rate in obese and nonobese people. J Am Diet Assoc. 2003;103(9):1152-1159, 2003.Direct validation showing standard Harris-Benedict within ±10% of measured RMR in ~67% of adults vs ~78% for Mifflin-St Jeor in the same cohort.
  7. Harris JA, Benedict FG — A Biometric Study of Basal Metabolism in Man. Carnegie Institution of Washington Publication No. 279, 1919.Original Harris-Benedict basal metabolism equations (1919) — historical baseline superseded by the 1984 revision for most modern adults.