What is Basal Metabolic Rate (BMR)?
Your Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to perform essential life‑sustaining functions while at complete rest. These functions include breathing, circulation, cell production, nutrient processing, and temperature regulation. BMR accounts for about 60‑75% of your total daily energy expenditure (TDEE).
Knowing your BMR helps you determine the baseline for weight management: if you eat fewer calories than your BMR plus activity, you lose weight; if you eat more, you gain weight.
BMR Formulas: Mifflin‑St Jeor vs. Harris‑Benedict
Mifflin‑St Jeor Equation (more accurate for modern populations):
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
Harris‑Benedict Equation (original, still widely used):
Men: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) – (5.677 × age)
Women: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) – (4.330 × age)
Both formulas provide a close estimate; Mifflin‑St Jeor is generally recommended for non‑athletic individuals.
BMR Calculation Example
Subject: 35‑year‑old female, height 165 cm, weight 70 kg.
- Mifflin‑St Jeor: BMR = 10×70 + 6.25×165 – 5×35 – 161 = 700 + 1031.25 – 175 – 161 = 1395.25 → ≈1395 calories/day
- Harris‑Benedict: BMR = 447.593 + 9.247×70 + 3.098×165 – 4.330×35 = 447.593 + 647.29 + 511.17 – 151.55 = 1454.5 → ≈1455 calories/day
The slight difference (≈60 calories) is normal; choose one formula and use it consistently to track changes.
How to Calculate Your BMR: Step‑by‑Step
- Gather your data: weight (kg), height (cm), age (years), and gender.
- Choose a formula – Mifflin‑St Jeor is recommended for most people.
- Apply the formula: for men, use +5; for women, use –161.
- Perform the multiplications and additions carefully.
- Your result is the estimated calories your body burns at complete rest in 24 hours.
- To get calories per hour, divide by 24.
Frequently Asked Questions About BMR
❓ What is the difference between BMR and RMR?
BMR (Basal Metabolic Rate) is measured under stricter conditions (complete rest, fasting, neutral temperature). RMR (Resting Metabolic Rate) is slightly higher and easier to measure. In practice, they are often used interchangeably.
❓ How can I increase my BMR naturally?
Building muscle mass (through strength training) increases BMR because muscle tissue burns more calories at rest than fat. Also, adequate protein intake and regular exercise can help maintain a healthy metabolism.
❓ Is BMR the same for everyone of the same weight and height?
No, factors like muscle mass, genetics, hormones, and health conditions cause individual variations. The formulas provide an average estimate.
❓ Should I eat below my BMR to lose weight?
Eating below your BMR is not recommended without medical supervision, as it can lead to muscle loss and metabolic slowdown. Instead, aim for a modest deficit below your TDEE (BMR + activity).
❓ Which formula is more accurate?
The Mifflin‑St Jeor equation is considered the most accurate for the general non‑obese population. Harris‑Benedict may overestimate BMR in some individuals.