All of us know that if we consume more calories than we use up each day, the extra calories will cause us to gain weight. But how do you know the amount of calories you need? Here’s how…
How many calories do you need everyday?
The total number of calories you burn in a day is known as your Total Daily Energy Expenditure (TDEE).
How many calories you need depends on a number of factors including height, total body weight, ratio of fat to muscle, age, gender, genes, physical exercise, and special conditions (e.g. illness, pregnancy, etc.). But usually, a woman’s calorie needs can be reasonably assessed by focusing on just two key calorie components: Basal Metabolic Rate (BMR), and amount of physical activity.
What is BMR?
Your Basal Metabolic Rate (BMR) is the total number of calories required to keep your body functioning while at rest (i.e. excluding all physical activities). This includes keeping your heart pumping blood throughout your body, inhaling and exhaling air, digesting food, making new blood cells, maintaining your body temperature and every other metabolic process and chemical reactions in your body. In other words, your BMR is all the calories used for the basic processes of life itself.
How to calculate your daily calorie needs or TDEE?
A commonly-accepted method for calculating TDEE is to first determine your basal metabolic rate (BMR) and then multiply the BMR by an activity multiplier to determine TDEE. There are 2 popular formulas that you can use — (1) Harris-Benedict Formula, and (2) Katch-McArdle Formula. We’ll show you both formulas so you can choose to use the one that’s more suitable for you.
(If you want to save time, please use the BMR/TDEE calculator below.)
(1) Harris-Benedict Formula (with BMR based on total body weight)
The Harris-Benedict equation is a calorie formula using the factors of gender, weight, height, and age to determine basal metabolic rate (BMR). There is a shortcoming to this formula though — it does not take into consideration lean body mass (LBM). Therefore, this equation will be very accurate in all but the extremely muscular (formula will underestimate calorie needs) and the extremely overweight (formula will overestimate calorie needs).
BMR = 655 + (9.6 X weight in kg) + (1.8 X height in cm) – (4.7 X age in years)
BMR = 655 + (4.354 X weight in lbs) + (4.569 X height in inches) – (4.7 X age in years)
And in case you are wondering, the formula for Men is:
BMR = 66 + (13.7 X weight in kg) + (5 X height in cm) – (6.8 X age in years)
BMR = 66 + (6.213 X weight in lbs) + (12.69 X height in inches) – (6.8 X age in years)
Now that you know your BMR, you can calculate TDEE by multiplying your BMR by your activity multiplier from the chart below:
Sedentary (desk job, with little or no exercise)
= BMR X 1.2
Lightly active (light exercise/sports 1-3 days/week)
= BMR X 1.375
Moderately active (moderate exercise/sports 3-5 days/week)
= BMR X 1.55
Very active (intensive exercise/sports 6-7 days/week)
= BMR X 1.725
Extremely active (intensive daily exercise/sports & physical job or twice per day training for marathon, races, fitness contests, etc.)
= BMR X 1.9
(2) Katch-McArdle Formula (with BMR based on lean body mass)
If you know your lean body mass, then you can use the Katch-McArdle formula to get the most accurate BMR estimate available. This formula takes into account lean body mass and is therefore more accurate than the Harris- Benedict formula which is based on total body weight. By the way, the Harris-Benedict formula uses different formulas for men and women because men generally have a higher LBM and this is factored into the men’s formula. Since the Katch-McArdle formula accounts for LBM, this single formula applies equally to both men and women.
BMR (men/women) = 370 + (21.6 X lean body mass in kg)
BMR (men/women) = 370 + (9.8 X lean body mass in lbs)
You weigh 130 lbs. (59.1 kg)
Your body fat percentage is 20% (26 lbs. fat, 104 lbs. lean)
Your lean body mass is 104 lbs. (47.3 kg)
Your BMR = 370 + (21.6 X 47.3) = 1392 calories
To determine TDEE from BMR, you simply multiply BMR by the activity multiplier (which is the same as those used in the Katch-McArdle formula above)
Online BMR/TDEE Calculator
We’ve created a free and simple-to-use online BMR/TDEE Calculator for your convenience. To start using the calculator, just check the BMR/TDEE calculator below, plug in the necessary information (e.g. your weight, height, age, lean body mass, etc), and the calculator will do the rest.
Some important points to note
It is very important to note that the higher your lean body mass is, the higher your BMR will be. Muscle is metabolically-active tissue, and it requires a great deal of energy just to sustain it. By doing strength/weight training, you will be building up your muscles (i.e. lean body mass) and this will in turn increase your BMR, which then leads to an increase in your TDEE. This is significant to you if you want to lose body fat because it means that the more muscle you have, the more calories you will burn.
Another thing you may have noticed from the Harris-Benedict formula is that your BMR gets lower the older you get. No wonder you are putting on the pounds as you get older, even if you haven’t changed your exercise and diet! Thankfully, this is something you can do something about.