HEALTH · RESTING METABOLIC RATE CALCULATOR (MIFFLIN-ST JEOR)
Resting Metabolic Rate Calculator (Mifflin-St Jeor)
Calculate your resting metabolic rate (RMR) using the Mifflin-St Jeor equation — the most clinically validated method for adults. Optionally add lean body mass for the Cunningham formula, which is more accurate for athletes.
Mifflin-St Jeor (1990) is the most clinically validated RMR equation. Multiply by your activity factor to estimate total daily energy expenditure (TDEE). Actual RMR varies with body composition, health status, and other factors.
About This Calculator
Resting Metabolic Rate (RMR) is the number of calories your body burns to maintain basic physiological functions — breathing, circulation, temperature regulation, and cellular repair — while at rest. This calculator uses the Mifflin-St Jeor equation (1990), which has been validated as the most accurate general-population RMR prediction equation in multiple systematic reviews. Athletes who know their lean body mass can use the optional Cunningham formula, which is based on fat-free mass rather than total weight and is more accurate for highly muscular individuals.
How It Works
Enter your height (cm), weight (kg), age (years), and biological sex. The calculator applies the Mifflin-St Jeor formula and returns your RMR in kcal/day. Optionally, enter your lean body mass (kg) to also see the Cunningham RMR estimate and your implied body fat percentage. To convert RMR to TDEE (total daily energy expenditure), multiply by your activity factor (1.2 sedentary to 1.9 very active).
The Formula
RMR = 10·weight(kg) + 6.25·height(cm) − 5·age + s
- weight
- Body weight in kilograms
- height
- Height in centimetres
- age
- Age in years
- s
- Sex constant: +5 (male) or −161 (female)
Frequently Asked Questions
- What is the difference between RMR and BMR?
- Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) are very similar and often used interchangeably. BMR is measured under strict conditions — complete rest, fasting, thermoneutral environment — making it a laboratory measurement. RMR is measured under less strict conditions and is typically 10–20% higher. In practice, both terms refer to roughly the same concept — calories burned at rest.
- Why is Mifflin-St Jeor preferred over Harris-Benedict?
- Both equations predict RMR from height, weight, age, and sex. Multiple systematic reviews have found that the Mifflin-St Jeor equation (published 1990) more accurately predicts measured RMR in modern populations than the original Harris-Benedict equation (published 1918) or the Harris-Benedict revision (1984). Mifflin-St Jeor has a mean prediction error of roughly 5% in non-obese adults.
- When should I use the Cunningham formula?
- The Cunningham formula uses lean body mass rather than total weight, making it more accurate for athletes and highly muscular individuals who have low body fat. If you have a DEXA scan result or other measured lean body mass, enter it to see the Cunningham estimate alongside Mifflin-St Jeor.
- How do I convert RMR to total daily calories?
- Multiply RMR by an activity factor. Standard factors are 1.2 for sedentary (desk job, little exercise), 1.375 for lightly active (light exercise 1–3 days/week), 1.55 for moderately active (exercise 3–5 days/week), 1.725 for very active (hard exercise 6–7 days/week), and 1.9 for extremely active (very hard exercise and physical job). The TDEE calculator on this site does this step for you.