Macro Calculator - Prospre (2024)

Your basal metabolic rate, or BMR for short, is an estimate of the number of calories your body burns each day with its normal functions, and excludes any exercise. The chart below, sourced from a 1981 report from the United Nations, details what those BMR calories are used for. While BMR varies from person to person (and even varies for a particular person from day to day), it can be estimated with reasonable accuracy based on body size and composition. For this estimation, several formulas exist to perform the calculation. The three most common formulas are Harris-Benedict, Mifflin-St. Jeor, and Katch-McArdle. For each of the formulas below,

BMR is the basal metabolic rate in Calories (kcal),
m is body mass in kg,
h is height in cm,
a is age in years,
BF% is body fat percentage.

The Harris-Benedict was one of the earliest formulas developed for BMR, with the original formula being published in 1918. The original formula they came up with was as follows:

For men, BMR = 13.7516m + 5.0033h - 6.7550a + 66.4730
For women, BMR = 9.5634m + 1.8496h - 4.6756a + 655.0955

In 1984, Roza and Shizgal revised the Harris-Benedict parameters, by using more accurate modern techniques to measure calories burned. Their revised formula was as follow:

For men, BMR = 13.397m + 4.799h - 5.677a + 88.362
For women, BMR = 9.247m + 3.098h - 4.330a + 447.593

Due to the increased accuracy, this revised formula should always be used when calculating BMR using Harris-Benedict.

In 1990, Mifflin and St. Jeor developed a simpler formula for BMR. This simpler formula uses largely the same parameters for both men and women, making it less complicated, and, on top of this, has been found to be about 5% more accurate for estimating BMR than Harris-Benedict. This improved accuracy may be due to changes in average lifestyles over the course of the 20th century. The Mifflin-St. Jeor formula is as follows:

BMR = 9.99m + 6.25h - 4.92a + c
where c is +5 for men and -161 for women.

Mifflin-St. Jeor is generally the recommended formula to use for BMR when a simple formula is desired, as more accurate formulas require more difficult to measure quantities like body fat percentage.

In 2006, Katch and McArdle developed a formula for BMR in their textbook Essentials of Exercise Physiology. This formula attempts to make a more accurate estimation by making use of the subject's lean body mass in the formula. To do this, a measure of body fat percentage is needed. When using this formula, it is important to measure body fat percentage using a formal method, as many people greatly underestimate their own body fat percentage when simply approximating based on pictures. The Katch-McArdle formula is calculated as shown below:

BMR = 21.6m x (1 - BF% / 100) + 370

If you know your body fat percentage with a high degree of confidence, Katch-McArdle is likely the best formula to use.

Since TEF is less significant in impact than TEA, and since TEF is much more complex to accurately estimate, formulas for calculating TDEE usually combine these values into a single number called the physical activity factor. This physical activity factor is determined by estimating a person's physical activity level, and choosing the corresponding value from a table of known values. The PAF is then multiplied by BMR to determine TDEE. This factor falls between 1.1 and 2.0 for the vast majority of people.

This is the method that is used by the calculator above. While this method may not be perfect, it is generally sufficient as a TDEE approximation, and if more precision is needed, one can monitor how their weight changes based on their diet and exercise, and use that to derive an estimate specific to their own lifestyle and physiology.

In order to lose weight, your caloric intake must be less than your TDEE. Conversely, if you want to gain weight, you need to eat more calories than your TDEE. The difference between the calories you eat and your TDEE will determine the rate that your weight changes.

But how much should you change your calories from your TDEE? Well, it depends on your goal.

If you are trying to lose weight, the general recommendation is that sustainable weight loss should be relatively gradual. This is to ensure the lost weight is from fat and not muscle, that there is no nutrient deficiencies, and that the diet is more likely to lead to sustainable lifestyle changes. One pound of weight loss per week is usually a good gradual goal.

How much of a caloric surplus is best for weight gain? Assuming that you want to gain mostly muscle and not fat, this should also be done gradually. For a fairly lean bulk, half a pound per week is a reasonable goal.

So how do these weight goals translate to calories? That depends on a lot of factors, but one common approximation is to convert the muscle or body fat you want into calories, and then target that amount for a calories surplus or deficit.

Many of you have probably heard it mentioned that a pound of body fat is roughly 3500 calories. But where does that number come from?

After all, we know that one gram of dietary fat is roughly 9 calories. One pound is about 454g, and 454 x 9 = 4086 calories. Why is that so much higher than 3500?

Well, the answer it turns out is that body fat is stored as more than just pure fat. It also contains some water and connective tissue. Studies have found that ~87% of fat tissue is pure fat. 87% of 4086 is 3555 calories, which is pretty close to the 3500 calorie figure we are used to.

Therefore, roughly 500 less calories per day should work to lose 1lb per week.

A naive approach here might be to consider how many calories are in a pound of protein. This would lead you to make an incorrect estimate of 454 x 4 = 1816 calories.

However, as you probably know from your own nutrition knowledge, 100g of meat does not contain 100g of protein. To add muscle, your body needs to build and repair muscle tissue, which involve protein synthesis, tissue accretion, and other processes which require additional energy beyond the energy density of the muscle.

We can easily loop up the amount of calories in a pound of animal muscle. Lean pork chops contain 744 calories per pound, and chicken breast is 748 calories per pound.

Is human muscle similar? Indeed it is, as studies have estimated human muscle to be roughly 700 calories per pound. However, while a caloric deficit translates fairly well for fat loss, simply eating 700 more calories per week will not result in muscle gains of one pound per week.

As mentioned above, muscle growth involves building muscle tissue, as opposed to fat which is simply stowed away for use later. This process of building new tissue (and repairing existing tissue) takes energy which requires more calories. So how many calories does building a pound of muscle take? Estimates have put it at around 2000-2500 calories.

However, when bulking, 100% muscle gain is not realistic - some fat will be gained as well. As a trade off between gaining muscle fast and not gaining fat, a decent goal is half a pound of fat for each pound of muscle. So, to gain one pound of muscle, you are looking at 3750-4250 surplus calories.

Therefore, a 250 calorie surplus should work for gradual, but steady gains of around 2lb of muscle per month.

As you might have noticed, plenty of common diets give macros well outside of these ranges. Most notably, the keto diet is much lower on carbs and much higher on fat.

So, is it safe to eat a diet outside of these ranges? That remains an active area of research.

If you do plan on going outside these ranges, especially if by a significant amount, you should consult a medical professional. In particular, you should make sure you are getting enough protein and fat, so that you are getting enough essential amino acids and essential fatty acids, among other reasons.

Protein is an essential nutrient, which you cannot live without. In particular, essential amino acids, which your body cannot create itself, are needed to build and repair tissue.

However, for most people in developed countries, eating too little protein is rarely a concern. Most people in those countries eat well in excess of 10% of their calories from protein.

That doesn't mean that you still can't benefit from adding more protein to your diet. After all, many people in developed countries aren't worried about malnourishment - they want to lose fat and/or build muscle. Higher protein diets can help with both of these goals.

Many people find that protein helps improve satiety to decrease hunger, and protein is known to increase calories burned as a result of the TEF. Muscle growth (hypertrophy) also requires sufficient protein to be achieved.

So how much should you eat? If you are going by a percentage of calories, 25% should be enough for most people's goals. Some bodybuilders or athletes may want to increase that a bit to ensure they are maximizing their potential.

You will often see protein recommendations given not as a fraction of calories, but instead in relation to body weight. Typically, these recommendations fall in the range of 0.7-1.0 grams per pound (1.5-2.2g/kg). This also works, and will usually have a similar percentage of calories to the 25% recommendation.

What about more than 35% protein? It's probably not necessary, even for muscle growth. For example, a 180lb man trying to lose weight by eating 2000 calories per day would still be able to eat 175g of protein per day at 35%. That's roughly one gram per pound of body weight, which is generally considered sufficient for muscle growth.

For fat, you want to make sure that you are eating enough so that you get a sufficient amount of essential fatty acids and are able to easily absorb fat soluble nutrients.

For this, your best bet is probably to just aim for the middle of the range given by the USDA. 25-30% should be fine for most people.

A bigger concern when it comes to fat is the type of fat. Trans fats should be avoided as much as possible, and saturated fats should be kept to about 5-6% of total calories.

Increased intake of omega-3 fatty acids, such as those in fatty types of fish, appears to be beneficial as well.

Opinions on how many carbohydrates you should eat vary greatly. The popular keto diet recommends as low as 5% of calories from carbs, while the high end of the range for the USDA AMDRs is 65%. That's a huge range.

If you followed the macro splits for protein and fat given above, you are left with 45-50% of calories from carbs. That will probably be fine for most people.

Lower carb diets, from moderately low carb (e.g., 40% of calories) to extremely low carb (i.e., keto), have been a topic of a lot of recent study. Some benefits of low carb diets, particularly for weight loss, have been observed, but more research is needed for conclusive evidence.

One downside of low carbohydrate diets is that some people find that it can reduce their energy levels, which makes them less able, or less motivated, to complete their workouts. Endurance athletes may find that they prefer more carbs to perform at their best.

Finally, much like with fat, not all carbs are created equal. Many people eat too many refined carbs, like sugar or starch, but not enough complex carbs like fiber. Soluble fiber in particular has been linked to benefits for heart health, and insoluble fiber can aid in digestion.