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RMR Calculator

Health

Calculate your Resting Metabolic Rate (RMR) using the revised Harris-Benedict equation. Find out how many calories your body burns at rest each day.

Reviewed by the thecalcu.com team · Last updated July 3, 2026

1580
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RMR (kcal/day)

1,492
RMR (kJ/day)
6,241
Calories per Hour
62.2

This calculator computes your RMR (kcal/day), RMR (kJ/day), Calories per Hour from the values you enter.

Inputs
GenderAgeWeightHeight
Outputs
RMR (kcal/day)RMR (kJ/day)Calories per Hour

What is a RMR?

An RMR Calculator estimates your Resting Metabolic Rate, the number of calories your body burns each day simply to keep essential systems running: breathing, circulation, cell repair, and maintaining body temperature. RMR typically makes up the largest single share of your total daily calorie burn, often 60-75% for most adults, which makes it a foundational number for anyone planning nutrition around weight loss, maintenance, or muscle gain. This calculator uses the revised Harris-Benedict equation, one of the most established formulas in clinical nutrition, alongside the newer Mifflin-St Jeor equation used in the BMR Calculator.

RMR is closely related to Basal Metabolic Rate (BMR), and the two terms are frequently used interchangeably. The technical distinction is that BMR requires strict laboratory conditions, a full overnight fast and complete physical rest, while RMR measurements are typically taken under slightly less controlled conditions, making RMR marginally easier to estimate in everyday settings and slightly higher in practice.

Why Use an RMR Calculator?

Knowing your RMR gives you a concrete floor for daily calorie planning, a number below which you shouldn't drop your intake for sustained periods, since your body needs that energy for basic function regardless of activity level. It's the essential first step before calculating your full TDEE, which adds your activity level on top of RMR to determine your true maintenance calories.

This is particularly useful if you're designing a calorie deficit or surplus plan and want to avoid cutting so aggressively that you risk muscle loss or metabolic slowdown, or if you're simply curious how factors like age, weight, and sex shape your baseline energy needs.

Who Should Use This Calculator?

  • Anyone starting a weight loss or weight gain plan who wants a scientifically grounded floor for their daily calorie target.
  • Strength trainers and athletes curious how muscle mass and body composition changes affect their resting energy needs over time.
  • People comparing RMR and BMR calculators who want to understand how the two closely related but distinct formulas differ.
  • Dietitians and nutrition students looking for a quick reference calculation using the standard revised Harris-Benedict formula.
  • Anyone recovering from illness or a period of inactivity who wants to understand their new baseline energy needs, alongside the Quarantine Activity Calculator.

What Insights Does the RMR Calculator Give You?

  • RMR (kcal/day), your estimated resting calorie burn per day; this is the primary result and the number to use as a baseline before adding activity.
  • RMR (kJ/day), the same result converted to kilojoules, useful for regions and food labels that use kilojoule units.
  • Calories per Hour, your RMR broken down to an hourly rate, useful for understanding how continuous your baseline calorie burn is throughout the day.

How to use this RMR calculator

  1. Select your Gender, this determines which version of the Harris-Benedict formula is applied.
  2. Enter your Age in years.
  3. Enter your Weight in kilograms.
  4. Enter your Height in centimeters.
  5. Review your RMR result, then use it as the starting point for a TDEE Calculator or Calorie Calculator to determine your full daily calorie target.
Show formula & methodology ↓Show less ↑

Formula & Methodology

Revised Harris-Benedict equation (Roza & Shizgal, 1984):

Men: RMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age in years)
Women: RMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) − (4.33 × age in years)

Worked example: A 28-year-old man, 80 kg, 178 cm:

RMR = 88.362 + (13.397 × 80) + (4.799 × 178) − (5.677 × 28)
RMR = 88.362 + 1,071.76 + 854.22 − 158.96 ≈ 1,855 kcal/day

This means his body burns approximately 1,855 calories per day at complete rest, before any activity is added.

Frequently Asked Questions

What is RMR?
RMR stands for Resting Metabolic Rate, the number of calories your body burns each day just to keep basic functions running while at rest, such as breathing, circulation, and cell repair. It's typically measured or estimated shortly after waking, without recent food intake or exercise.
What is the difference between RMR and BMR?
BMR (Basal Metabolic Rate) is measured under strict laboratory conditions, completely fasted, fully rested, in a thermoneutral environment, while RMR is a slightly less strict measurement that can be taken under more normal conditions. In practice, RMR is usually 5-10% higher than BMR because the measurement conditions are less controlled, but the two terms are often used interchangeably in everyday calculators.
What formula does this RMR calculator use?
This calculator uses the revised Harris-Benedict equation (Roza & Shizgal, 1984), which estimates resting energy expenditure from your weight, height, age, and sex. It's one of the most widely cited formulas in clinical nutrition, alongside the Mifflin-St Jeor equation used for BMR.
How accurate is the Harris-Benedict equation?
The revised Harris-Benedict equation is generally accurate within about 10% for most healthy adults, though it can be less precise for people at the extremes of body composition, such as those with very high muscle mass or very high body fat. For the most accurate reading, indirect calorimetry testing is the gold standard, but that requires clinical equipment.
Why does my RMR matter for weight management?
Your RMR typically accounts for 60-75% of your total daily calorie burn, making it the single biggest factor in your overall energy needs. Understanding your RMR helps you set realistic calorie targets for weight loss, maintenance, or gain rather than guessing.
Does muscle mass affect RMR?
Muscle tissue burns more calories at rest than fat tissue, so people with higher muscle mass generally have a higher RMR at the same body weight. This is one reason strength training can help support a higher metabolic rate over time.
How do I increase my RMR?
Building lean muscle mass through resistance training is the most reliable way to raise your RMR over time, since muscle tissue is more metabolically active than fat. Adequate protein intake and avoiding severe, prolonged calorie deficits also help preserve the muscle mass that supports a higher resting metabolism.
Does RMR decrease with age?
Yes, RMR typically declines gradually with age, partly due to natural loss of muscle mass over time. This is reflected in the age term of the Harris-Benedict formula, which reduces the calculated RMR as age increases.
Should I eat below my RMR to lose weight faster?
No, eating consistently below your RMR is not recommended, since your body needs that minimum energy just to maintain basic organ function, and severe restriction can slow metabolism and cause muscle loss. Sustainable weight loss plans typically target a moderate deficit below your full TDEE, not below RMR alone.
How is RMR used to calculate my total daily calorie needs?
RMR is the starting point, you then multiply it by an activity factor that accounts for exercise and daily movement to get your Total Daily Energy Expenditure (TDEE). Use the [TDEE Calculator](/tdee-calculator/) to take that next step once you know your RMR.
Is RMR the same for men and women at the same weight?
No, men typically have a higher RMR than women at the same weight and height, largely because men tend to carry more lean muscle mass and less body fat on average. The Harris-Benedict formula uses separate equations for men and women to reflect this difference.
Can I lower my calorie intake based on my RMR result?
Your RMR gives you a baseline, but your actual calorie target for weight loss or gain should be based on your full TDEE (RMR plus activity), not RMR alone. Use this result alongside a [Calorie Calculator](/calorie-calculator/) or [TDEE Calculator](/tdee-calculator/) to set a realistic daily target.
Also known as
resting metabolic rate calculatorRMRresting energy expenditureHarris-Benedict calculatorcalorie burn at rest