What is the Harris-Benedict formula?

The original Harris-Benedict equation was published in 1919 and revised by Roza and Shizgal in 1984. The revised version: For men: BMR = 88.362 + (13.397 × kg) + (4.799 × cm) - (5.677 × age). For women: BMR = 447.593 + (9.247 × kg) + (3.098 × cm) - (4.330 × age). It tends to slightly overestimate BMR compared to Mifflin-St Jeor.

Which activity level should I choose for TDEE?

Choose Sedentary (1.2x) if you have a desk job with little exercise. Lightly Active (1.375x) if you exercise 1-3 days per week. Moderately Active (1.55x) for 3-5 days per week of moderate exercise. Very Active (1.725x) for hard exercise 6-7 days per week. Extra Active (1.9x) for very intense exercise plus a physically demanding job.

BMR Calculator — Basal Metabolic Rate & TDEE

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Formula

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Age (years)

Weight (kg)

Height (cm)

Height (ft & in)

Your Results

Basal Metabolic Rate (BMR)

Calories your body burns at complete rest per day

Daily Calorie Needs by Activity Level (TDEE)

Activity Level	Calories/Day
Calculate to see TDEE

Calculation Assumptions

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Weight entered: --
Height entered: --
Age / Sex: --
Converted weight: --
Converted height: --

About This Calculator

What it calculates: Basal Metabolic Rate (BMR) in kcal/day and Total Daily Energy Expenditure (TDEE) across 5 activity levels.
Inputs required: Sex (male/female), age (15–100 years), weight (20–300 kg or 44–660 lbs), height (50–250 cm or 20–98 total inches).
Outputs: BMR in kcal/day; TDEE at Sedentary (×1.2), Lightly Active (×1.375), Moderately Active (×1.55), Very Active (×1.725), Extra Active (×1.9).
Mifflin-St Jeor formula (default): Male: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5. Female: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161.
Harris-Benedict formula (revised 1984): 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).
Last updated: March 2026

What is BMR and How Does This Calculator Work?

Basal Metabolic Rate (BMR) is the number of calories your body needs to sustain essential physiological functions — breathing, heartbeat, circulation, cell production, body temperature regulation, and brain activity — while at complete rest for 24 hours. BMR represents the minimum energy requirement to keep you alive.

Understanding your BMR is the foundation of nutritional planning. It tells you how many calories your body burns doing absolutely nothing. Combined with your activity level to get your Total Daily Energy Expenditure (TDEE), BMR gives you a scientifically grounded baseline for setting calorie intake goals — whether for weight loss, maintenance, or muscle gain.

This calculator supports two widely validated formulas — Mifflin-St Jeor (recommended default) and Harris-Benedict (revised) — and accepts both metric (kg/cm) and imperial (lbs/ft-in) inputs. All calculations run in your browser with no data stored.

How to Use This Calculator

Select your unit system: Choose Metric (kg and cm) or Imperial (lbs, feet, and inches).
Choose a formula: Mifflin-St Jeor is the default and is considered the most accurate for most adults. Harris-Benedict (revised) is also available for comparison.
Enter your details: Select your sex, enter your age, weight, and height.
Click Calculate: Your BMR appears in kcal per day, followed by a TDEE table for 5 activity levels.
Find your TDEE: Match your activity level in the table to see how many total calories you burn daily.

BMR Formulas with Variable Definitions

Mifflin-St Jeor Equation (1990)

Published by Mifflin et al. in 1990, this is the most widely recommended BMR formula for the general adult population. Studies show it estimates BMR within 10% of measured metabolic rate for most people.

Male BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5

Female BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161

Where: weight is in kilograms, height is in centimetres, age is in years. The constant (+5 for males, −161 for females) accounts for the sex difference in metabolic rate.

Harris-Benedict Equation (Revised 1984)

Originally developed by Harris and Benedict in 1919 and revised by Roza and Shizgal in 1984, this equation is still widely used in clinical settings and nutrition research.

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)

Harris-Benedict tends to estimate BMR approximately 5% higher than Mifflin-St Jeor. For most non-obese adults, both formulas give similar results.

TDEE Activity Multipliers

Total Daily Energy Expenditure is calculated as: TDEE = BMR × Activity Multiplier

Sedentary (×1.2): Desk job, no exercise, minimal daily movement.
Lightly Active (×1.375): Light exercise or sports 1–3 days per week.
Moderately Active (×1.55): Moderate exercise 3–5 days per week, or manual job.
Very Active (×1.725): Hard exercise 6–7 days per week, or active construction/trade job.
Extra Active (×1.9): Very intense daily exercise plus a physically demanding job (e.g. athlete in training).

Unit Conversion Used Internally

If you enter imperial measurements, the calculator converts them before applying the formula:

Pounds to kilograms: kg = lbs × 0.453592
Feet and inches to centimetres: cm = (feet × 12 + inches) × 2.54

BMR vs TDEE: What's the Difference?

BMR is a theoretical baseline — the calories you'd burn lying completely still in a temperature-controlled room, not even digesting food. In practice, you always burn more than your BMR.

TDEE (Total Daily Energy Expenditure) is the more practical number. It includes:

BMR (60–75% of TDEE) — resting metabolism
TEF (Thermic Effect of Food, ~10%) — calories burned digesting food
NEAT (Non-Exercise Activity Thermogenesis, ~15–30%) — movement from walking, fidgeting, daily tasks
EAT (Exercise Activity Thermogenesis) — structured workout calories

To lose weight, consume fewer calories than your TDEE. A 500 kcal/day deficit leads to approximately 0.45 kg (1 lb) of fat loss per week. To gain muscle, consume 250–500 kcal above TDEE while following a resistance training programme. To maintain weight, eat at TDEE.

Worked Examples

Example 1 — Male, Metric, Mifflin-St Jeor

Sex: Male | Age: 35 | Weight: 80 kg | Height: 178 cm
BMR = (10 × 80) + (6.25 × 178) − (5 × 35) + 5
BMR = 800 + 1,112.5 − 175 + 5 = 1,742 kcal/day
TDEE at Moderately Active (×1.55) = 1,742 × 1.55 = 2,701 kcal/day
To lose 0.5 kg/week: aim for approximately 2,200 kcal/day (deficit of ~500 kcal)

Example 2 — Female, Imperial, Harris-Benedict

Sex: Female | Age: 28 | Weight: 140 lbs | Height: 5'5" (65 inches)
Convert: 140 lbs × 0.453592 = 63.5 kg | 65 in × 2.54 = 165.1 cm
BMR = 447.593 + (9.247 × 63.5) + (3.098 × 165.1) − (4.330 × 28)
BMR = 447.593 + 587.18 + 511.47 − 121.24 = 1,425 kcal/day
TDEE at Lightly Active (×1.375) = 1,425 × 1.375 = 1,959 kcal/day

Frequently Asked Questions

BMR is the number of calories your body burns at complete rest to maintain essential functions such as breathing, circulation, cell production, and temperature regulation. It represents the minimum energy requirement to sustain life. BMR typically accounts for 60 to 75 percent of total daily calorie expenditure.

BMR is calories burned at rest, while TDEE (Total Daily Energy Expenditure) includes all physical activity throughout the day. TDEE is calculated by multiplying your BMR by an activity multiplier ranging from 1.2 (sedentary) to 1.9 (extra active). TDEE is the number of calories you need to maintain your current weight.

The Mifflin-St Jeor equation, published in 1990, is considered the most accurate BMR formula for most adults. For men: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5. For women: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161. It is the default formula used by most dietitians and healthcare professionals today.

The revised Harris-Benedict equation (Roza & Shizgal, 1984): For men: BMR = 88.362 + (13.397 × kg) + (4.799 × cm) - (5.677 × age). For women: BMR = 447.593 + (9.247 × kg) + (3.098 × cm) - (4.330 × age). It tends to slightly overestimate BMR compared to Mifflin-St Jeor.

To lose weight, you need to consume fewer calories than your TDEE. Find your TDEE using your BMR and activity level. A deficit of 500 calories per day leads to approximately 0.5 kg of fat loss per week. Do not eat below your BMR for extended periods, as this can slow metabolism and cause muscle loss.

Yes. BMR decreases with age, primarily because of the natural loss of lean muscle mass (sarcopenia). After age 30, BMR typically declines by 1 to 2 percent per decade. Regular resistance training helps preserve muscle mass and reduces the rate of BMR decline.

Yes. Men generally have a higher BMR than women of the same age, height, and weight because men typically have more lean muscle mass and less body fat. Muscle tissue burns more calories at rest than fat tissue.

Choose Sedentary (1.2×) if you have a desk job with little exercise. Lightly Active (1.375×) if you exercise 1–3 days per week. Moderately Active (1.55×) for 3–5 days per week of moderate exercise. Very Active (1.725×) for hard exercise 6–7 days per week. Extra Active (1.9×) for very intense exercise plus a physically demanding job.

Important Notes

BMR formulas are population-based regression equations and provide estimates, not exact measurements. Individual metabolic rate can vary by ±10–15% from calculated BMR due to genetics, body composition, hormonal factors, and health conditions. For a precise measurement, a registered dietitian can perform indirect calorimetry.

These formulas are validated for adults aged 18–80. They may be less accurate for individuals who are significantly obese (BMI above 40), for competitive athletes with very high muscle mass, or for people with metabolic disorders such as hypothyroidism.

BMR and TDEE are starting points. Monitor your weight over 2–4 weeks after applying your target calorie intake and adjust as needed based on real-world results.

Calculator Category

This tool belongs to Health Calculators. Browse similar tools for related calculations.

Results are for informational purposes only and do not constitute medical or nutritional advice. Consult a qualified healthcare professional or registered dietitian for personalised guidance.

BMR Calculator