The Mifflin St Jeor Calculator

This a classic formula and is the initial one we use to determine your caloric needs. It is going to require you to do a little math, but it's not too complicated.

 

First, you have to know your weight in kilograms. If you have a digital scale (or even some analog scales that have kilograms listed), this is pretty easy. You select the metric measurement and hop on. If you don't have that option, all you need to do s divide your weight in pounds by 2.2. So if you weigh 132 lbs, your equation would look like this.

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132 / 2.2 = 60 kg

Your weight would be 60k in that case.

Next, you have to figure out your height in centimeters. One inch equals 2.54 centimeters. So if you're 5 feet tall, your equation to figure out your height in centimeters would be as follows:

(12in x 5ft) x 2.54 = 152.4cm

So we figured out our height in inches and from there, centimeters.

 

Now we can figure out your BMR (base metabolic rate) according to the Mifflin St Jeor equation.

 

For men:

(10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5 = BMR

 

For women:

(10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161 = BMR

 

 We'll use a 100kg man for our first equation. Let's say he is 25 years old and 182 cm.

10 x 100 + 6.25 x 182 – 5 x 25 + 5 = 2017.5

(Round up to 2018)

 

There's our man's BMR, now let's figure it out for a 60kg woman, aged 25, 5 feet tall—the equation is slightly different.

10 x 60 + 6.25 x 152.4 – 5 x 25 – 161 = 1266.5

 

Activity Factor

Alright, now that you have established your BMR, it's time to figure out your maintenance calories. To do that, you take your BMR and add in the calories you burn when you exercise and play sports. The figure will always be higher than your BMR and is based on a range starting at 1.2 up to 1.9.

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1.2 – Sedentary: You work a desk job and do not exercise (probably not many of you)

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1.375 Light Activity: You work a desk job but do a bit of regular exercise. Or you do a little exercise, but you work an active job (i.e., A nurse, teacher, etc.) where you're on your feet most of the day. Most of you here are decently active.

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1.55 – Moderate Activity: Most of you will probably fall into this category. Maybe you work a sedentary job but train like a madman. Or perhaps you train moderately but have a position where you stand on your feet most of the day. Someone who does not train but works a hard labor job would fall into this category as well.

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1.725 – Very Active: You train most days of the week hard, and you also work a job where you are on your feet quite a bit. Overall, you're active throughout most of the day.

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1.9 – Extra Active: You train hard and work a job that is also intense. For example, maybe you are a roofer, but you also go to the gym five days a week.

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Once you select the appropriate activity factor, multiply it by your BMR you established above, and there you have your estimated maintenance calories. For our 60kg woman who used the Mifflin calculator, her maintenance calories would look like this:

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1267 x 1.55 = 1963.85

(Round up to 1964)

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Once you have your maintenance calories, subtract 500 calories to get your deficit. Your body requires a deficit of 3500 calories to lose 1 lb per week, so we divide that across the days of the week. For the same 60kg woman above, we would set her caloric deficit at 1464 calories per day.

 

Protein is set at 1g per lb of bodyweight (or lean mass if we have it), and fats are set at 20% daily caloric intake. 

1g Protein = 4 calories

1g Carbohydrate = 4 calories

1g Fat = 9 calories

So our 60kg woman, who is 132lbs, will get 132 g of protein, which equals 528 calories. For her fats, 20% of her 1464 calories is 293 calories, divided by 9 = 32 gram of Fat. That leaves us with 643 calories left over for carbs. 643/4 = 160.75 carbs and well round up to 161g. So her macros will look like this:

Protein: 132g

Carbs: 161g

Fat 32g