On top of that, in this calorie calculator, we talk about lost calories per day, how to burn more calories with fitness and explore the health benefits of exercising, such as the prevention of heart disease.

## What are calories?

Put simply, calories are a measure of energy. Traditionally, it was a fairly common unit of energy, but nowadays it's been relegated to describe almost solely nutrition and the energy content in food. The definition of a calorie is the energy required to raise the temperature of 1 gram of water by 1C. In modern times the definition of a calorie has been tuned and improved to a more reliable and repeatable one until we have arrived at the current: 1 calorie is equivalent to 4.18 joules.

In nutrition, we actually deal with kilocalories (kcal), where 1 kcal is equal to a thousand "small" calories. This kilocalorie is often called large calorie, Cal or Calorie (with capital 'C'). As you imagine, 1 kcal = 4.18 kJ. In this article, we use the term "calories" to describe kilocalories for simplicity.

When you mention calories, people immediately think about nutrition, weight loss, and even health problems associated with being overweight, such as heart disease. This is because body fat and calories are very closely related. Body fat is the way our body stores energy for times of necessity, that is, body fat is how we store those extra calories that we ate but never burned. Fat is not necessarily a bad thing, as we explained in our healthy body fat calculator

There is a simple way to calculate calories from fat, which is based on the energy density of body fat. Each kilogram of body fat stores about 7700 kcal. This equivalence is what allows the burned calories calculator to predict the weight loss derived from a certain exercise. However, this is just an oversimplification since "calories in vs calories out" is not the whole story when it comes to weight loss. We will go a bit more into details in a later section, for now, let's focus on the calculator.

## How to calculate calories burned?

Since calories are, effectively, energy, any time energy is used or transformed in our body, we consume calories. This includes those times in which we are apparently doing "nothing" since, fortunately for us, our body is still functioning and consuming energy. The energy is consumed in activities such as pumping blood through our system, processing food in our digestive system and even thinking (the brain burns about 20% of our daily calories). But when we talk about consuming calories we tend to think more about the conscious act of exercising and expending extra energy compared to the normal or basal metabolic levels.

As you may have guessed, every exercise needs a different amount of energy. The number of calories burned walking is smaller than running or cycling. This energy expenditure is typically expressed in `MET` - the Metabolic Equivalent of a Task. This measure tells you how many calories you burn per hour of activity and per one kilogram of body weight.

The MET value of an exercise is higher the more energy an activity requires. You can check that by looking at the different MET values for the exercises we have included in this calorie calculator. For example, sleeping has a value of 1 MET while running has a MET of 7.5, much higher.

What exactly is 1 MET, then? It is defined as the ratio of energy spent per unit time during a specific physical activity to a reference value of 3.5 ml O₂/(kg·min). While the MET values allow us to compare activities, they don't measure energy directly. So you need another step to answer the question how many calories do I burn a day doing certain activity?. Answering that requires some recalculation and for you to convert milliliters of oxygen to calories before we arrive at the final formula:

`calories = T * MET * 3.5 * W / (200 * 60)`

where T is the duration of activity in seconds, and W is your weight in kilograms.

Our calorie burn calculator uses the formula above for the most accurate estimation of calories burned. If you want to run your calculations by hand, you can also use a simplified version of this equation:

`calories = MET * T * W`

This equation is based on the approximation that `1 MET = 1 kcal / (kg * h)`. It is not 100% correct since the real equivalence is `1 kcal/(kg * h) = 1.05 MET`, as you can check from the initial formula. Nevertheless, the approximation simplifies calculations so much that a mere 5 percentage difference is an acceptable price to pay.

## How many calories did I burn while cycling?

If you want to calculate the weight loss or calorie loss after a certain physical activity, make sure to follow the steps below. We have chosen to calculate the calories burned cycling, but you could calculate the calories burned walking following these same steps.

1. Choose your activity and determine its MET value. For example, for cycling MET = 8.
2. Input your weight into the calories burned calculator. Let's assume you weigh 90 kg.
3. Determine the duration of the activity. Let's say you went for a whole day trip and were biking for 7 hours straight.
4. Input all of these values into the calorie burned formula:

`calories = T * 60 * MET * 3.5 * W / 200`

`calories = 7 * 60 * 8 * 3.5 * 90 / 200 = 6284 kcal`

1. Finally, divide this value by 7700 to obtain your weight loss:

`6284/7700 = 0.82 kg`

Congratulations! Your bike trip just helped you lose 0.65 kg. Now, it's time to head to the BMI calculator and check where you place, just remember, it's not a competition, just an indicator. You can also visit our Basal Metabolic Rate calculator which will tell you how many calories your body requires for its basic existence. It will be a reasonable basis for constructing a new diet plan.

## A deeper look at MET and the calorie calculator

Let's now step back a little bit and look at how MET is calculated and what it really means. MET is a metric that assigns a single value to a certain activity, but, as anyone that has run or cycled frequently knows, the same exercise can vary in intensity significantly depending on the effort. There is a difference between going for a leisure ride with your kid and racing in a criterium, even if they both take the same time.

This is an effect that this calculator does not take into account: intensity. It is for this reason that the calories burned calculator needs to be understood as an approximation and not as a precise measurement. The MET we have encoded into this tool are just a guide based on averages and typical values for a typical person.

However, one can correct for this issue by simply customizing the MET value directly. We do not recommend doing this unless you know what you are doing or you are using a comprehensive database of MET values. The important thing to remember is that the MET values are not the be-all-and-end-all and should be taken with a pinch of salt. They, however, help you compare easily the calorie consumption expected from different exercises and activities.

## BMR or how many calories per day you burn without doing anything

Another aspect that people tend to forget when thinking about how to calculate calories burned per day is the Basal Metabolic Rate or BMR, also called resting metabolic rate. BMR is a measurement of the minimal metabolic rate, or calories burned by "just being alive". It is defined as the calorie burning rate of an animal at rest. We can also see it as the lowest valid answer to the burning question of how many calories do I burn a day?

This value is surprisingly high in most people, being greater than 1000kcal and even over 3000kcal for professional athletes. As you might have noticed, we have singled out athletes as having a much higher than normal BMR, and that's for a reason: BMR is not a fixed value, it can vary from person to person.

Using very simplistic examples we can take a look at how the BMR changes for a person. When we exercise a lot not only do we need more calories to compensate for the expenditure during our activity but also we put our body into a more active rest state when the time comes to recover. Recover is the key word here since, at rest, our body not only has to keep functioning like any other person's but also has to recover from the exercise and rebuild energy stores and muscle tissue with the consequent increase in BMR.

On the other hand, we can lower our BMR by having a very sedentary lifestyle, which we do not recommend. On top of that, calorie intake has a significant effect on the BMR of a person since when we restrict the calorie consumption significantly, our body goes into what is called "starvation mode". In this state, the body senses a lack of food and adapts accordingly reducing the BMR as much as possible so that it can use those precious, finite calories to move or think.

This last effect is particularly counterproductive when trying to lose weight by reducing the food intake and it's the reason why many people can't seem to lose weight even when eating half as much as they did before. Starvation mode is also partly responsible for the rebound effect people experience after finishing a diet. We do not recommend losing weight by reducing the calorie intake unless you have professional advice since it can lead to nutrient deficiency and all the associated health risks.

## Burn more calories with these exercises

So now the question is: How do I burn more calories? The answer is, as always, it depends. There are two major ways to burn more calories depending on whether you are restricted by time or not. Assuming you don't have a time limit, the answer is as intuitive as it gets: exercise for longer. As you can see by using the calculator, the more time you dedicate to exercise, the more calories we burn in total.

However, most of us are usually restricted by the time we have available to exercise after taking care of our priorities like work, family... In this case, the answer is exercise with more intensity. The harder you train, the more calories you will burn. A higher running pace will burn more calories... But how long can you sprint? If you're truly sprinting, you shouldn't be able to go on for more than a minute, tops.

And this is the reason HIIT is so trendy right now. HIIT or High-Intensity Interval Training, is a way of structuring your exercises so that you can keep the intensity very high (as the name implies) but also keep up this intensity for a long time. The trick is to introduce periods of rest between high-intensity bursts. This method is by far the most efficient way to burn more calories and it's unbeatable in terms of calories per time exercising.

On top of the fact that you will consume a higher number of calories, HIIT has a second advantage. HIIT is a very efficient way to raise your BMR. During HIIT exercise we create micro-damage in our muscles (don't worry is all good) that the body later repairs, building a bigger and stronger muscle. This is how we get fitter and stronger and it's a process in which the number of calories burned at "rest" is greatly increased compared to steady-state cardio exercises, not to mention compared to a sedentary lifestyle.

HIIT comes in many forms, from taking any sport and breaking down the activity into intervals of mixed high intensity and low intensity (active recovery), to even weightlifting and fitness. It might sound counter-intuitive but the calories burned lifting weights can rival a full body exercise such as dancing when we take into account the total calories burned throughout the day. On top of that, and with proper nutrition, the calories burned lifting weights will also help you to build more muscle as well as to prevent heart disease.

## Burn calories and prevent heart disease with fitness

You might be thinking (especially if you're of a younger age) that the purpose of exercising and burning calories is mostly weight loss and fitness benefits. However, there's much more to exercising than looks and records. It is recognized by every doctor that regular exercise is the second best thing you can do for your health after quitting smoking (you will also save money by not smoking), and the very best thing if you're not a smoker.

Among the benefits of exercising we can point to psychological well-being and increased happiness, as well as physical health benefits such as an improved immune system, higher bone density and lowering the risk of heart disease. If we had to point to the most important benefits it would definitely be the psychological aspect as not only will exercise and burning calories make you happier (exercise releases endorphins)but it also decreases the suicide rates amongst all populations, a very good effect you must agree.

Together with a lower the risk of suicide, the reduced risk of suffering from heart disease has to be close to the top of the list as well. The improvement that exercise has on our cardiovascular system is very significant, and with heart disease being the leading cause of death for both men and women it is not something to sniff at. If you are interested in learning more about the heart and what it means to have a healthy one you can start by visiting our healthy heart rate calculator

But HIIT training and hardcore exercising "it's not for me" you might say. To you, I say: Don't fret! There's a solution. Luckily for us, our bodies are not very picky about the types of training that we do, so literally anything is better than nothing. Walking, dancing, recreational swimming... Anything that moves your body is a good way to start; so find something that you enjoy doing, and do it!

## Does sex burn calories?

So what about sex? Does sex count as active time? Does sex burn calories and improve my health? We have good news, the answer is YES! As any action involving motion, sex burns calories. So it might be a good option for you if you want to increase the number of calories that you consume per day. The only problem might be finding a willing partner.

Before you go into a sex to burn calories, let's take a look at how much sense it makes by looking at how many calories does sex burn. The reality is probably not simple since answering How many calories does an activity burn? accurately involves, once again: a big fat "it depends". As with any activity, it depends on your weight, intensity, the time you spend doing the activity, which means that sex burns calories at different rates depending on what and how you do it.

Let's not get it cheek-blushing details and just take a look at a typical encounter. According to statistics, the average sexual encounter lasts from seven minutes to a maximum average reported of under twenty minutes depending on the source. We will also take the average male weight in the USA (about 200 lbs), since it's higher than women, and therefore allows for a more general estimation of how many calories sex burns.

Putting these values together into our calorie calculator we get a result of about 190 kcal each time we have sex. Taking into account that most people are around a healthy sex frequency of once every week, this amount fails to be significant for any weight loss purposes. It is still better than nothing, but, now you know how many calories sex burns, it doesn't seem like sex burns calories at a rate that would be significant. Maybe you and your partner can make it work :)

## Let's get technical: Number of calories in food

Speaking of weight loss, which is the main reason most of you have landed on this calories burned calculator, let's turn our attention away from "how many calories did I burn?", and towards "how many calories per day do I consume?". You can get a rough answer with our macronutrients calculator or our meal calories calculator, but let's talk about dietary calories for a moment before we calculate anything.

If we talk in chemical terms, everything has calories. From a simple dish of pasta to even a glass of tap water, everything has some energy inside of it. However, our body cannot process and obtain all the energy in everything. To give an extreme example, the energy stored in Uranium atoms is enough to create the most powerful bomb in human history, however, if you were to eat Uranium you wouldn't have tons of energy, or get super fat. You would just die since it is also radioactive.

And that's why the concept of "dietary calorie" was brought into existence. Dietary calories refer to the amount of energy in an edible product to which our body has access. In water, for example, there are no dietary calories because all the energy is stored in its chemical bonds, simply because our body cannot obtain such energy. Luckily for us, when food manufacturers state the number of calories in a certain meal or product, they only write about dietary calories (generally kcal or Cal, to be precise), which means we don't need to make any calculations when watching our food intake.

Once we talk about dietary calories, we can start thinking about weight loss through diets. In very broad terms (purely thermodynamics terms for the most part), the weight loss game seems simple: Calories in minus calories out, and then convert to body fat weight lost or gained. The reality is much more complicated than that, as we will see later, but for now, let's focus on the tree main caloric states we can be in:

1. Caloric deficit,
2. Caloric balance,
3. Caloric surplus.

Caloric balance is the state in which the number of calories burned equals the number of calories taken. In the simplistic thermodynamics approach, this is the state in which we don't lose weight but we also don't gain any weight, we are at balance.

The next state is the caloric deficit, which is the most used tactic for losing weight. In this state we eat fewer calories than we burn, hence creating such a caloric imbalance. There are two main ways to achieve this imbalance: eating less and exercising more. You can also achieve this state by any combination of these two. Common sense dictates that this is the path to weight loss and fat burning, and that's mostly true. However, we will see in the next section all the understatements and objections that accompany this assumption.

Lastly, we have the caloric surplus, which is the state of eating more calories than we burn. This is the state used to gain weight, mostly in the form of fat. Nevertheless, weight gain doesn't necessarily mean getting fat as people in the fitness industry know very well. The practice of "bulking" within fitness refers to the practice of eating more calories than the calories burned by lifting weights, and therefore being in a caloric surplus state. All this is in the pursuit of muscle growth.

Bulking typically involves fat as well as muscle gains. This is technically not necessary since to gain muscle, caloric surplus is not needed only "nitrogen surplus" or protein surplus. Reality is more complicated as it can be very difficult to eat a lot of high protein foods without stepping in a caloric surplus.

This last fact about bulking suggests that the model "calories in minus calories out" is not the whole story. Let us move into the next section to clarify the nuances of calorie balance and weight loss.

## Do fats make you fat?

A calorie is a calorie, they say. It might seem right on first sight but the reality is actually different. For once, there is the obvious issue with the "size" of a dietary calorie. Do you know how many lettuces you have to eat to get 1000 kcal? On the other hand, if you're having a pizza party, you will find yourself exceeding that amount before you start to think you might have had enough.

Then there is the nutrition aspect of food. Our bodies need more than just calories to function, from macronutrients such as carbohydrates, proteins and fat, to micronutrients like vitamins and minerals. Meeting your body's requirements for these elements is crucial for a healthy life. So when it comes to getting calories, it matters what food you eat, not just the amount of calories.

And last but definitely not least is the hormonal side of eating. This is a complex topic that requires intensive knowledge of biology and medicine, and so it is often overlooked. However, as time passes and more and more studies come out, the scientific community realizes the importance of understanding the relationship between food and hormones.

In short, there are certain types of hormones that promote different functions in our bodies such as fat burning, fat storage and even changes in your BMR. Taking all these factors into consideration is crucial to understand how your body reacts to food intake, and will help you achieve your ideal weight while staying healthy, and preventing any future problems or side effects. Fats are not always bad.

So coming back to "a calorie is a calorie" let's use an analogy to understand why fats are not always bad. While that's true technically, it's also very wrong and misleading. You can compare the idea of "calories in vs calories out" for weight loss and say that the way to get rich is to "spend less than you earn". Yes, it is true; but it hides the underlying complexity of the problem while offering very little practical help to anyone willing to lose weight (or get rich).

We are obviously not saying that the calories burned or eaten don't matter, as with the case of getting rich you need to tick that box as a prerequisite. But next time you try to lose weight, don't think just about your calories burned against your calories eaten. Instead, do a little bit of research, eat healthy food and, if you can, get professional help.

## Fun fact: how you lose weight when you sleep

And lastly, let's take a look at a fun fact about weight loss without necessarily involving exercises or burning calories. It is common knowledge that we are lighter in the morning than we were at night the day before. This seems like a bit of a mystery at first sight since it happens even if we don't go to the bathroom in the middle of the night. Let's take a look at where has that weight gone and why is this effect happening to all of us more or less equally.

First of all, we should explain the premises. You can even try this at home if you're feeling skeptical. Get ready for bed, put on your pajamas, do anything you do before slipping into your comfortable bed, but just before you do so weigh yourself on your home scale. Right down the value and repeat the process in the morning, first thing after waking up.

Note that it won't work if you go to the bathroom in the middle of the night or if you pay a cheeky visit to the fridge in the safety of the dark. Assuming you've followed the steps correctly, the reading you get in the morning should be lower than before going to sleep. You can even do this several days in a row and you'll see the same effect.

When asked for a possible explanation of this effect, people quickly point at Einstein's mass energy equivalence. Though Einstein's equation is much more subtle than any process of weight loss occurring in our body, this is not a bad guess. In some (very non-physics like) sense, that's what happens when we burn calories and as a result, we lose weight.

However, the real reason why we wake up lighter in the morning is much more interesting and easy to understand with just the most basic knowledge of science. By process of elimination, we could narrow down the possible causes to the only two mechanisms in which we exchange matter with the outside while sleeping: sweating and breathing. But sweating doesn't always happen at night and the weight loss can be found even in the coldest of nights with barely any cover on.

So... It must be breathing! Shocked? You should be, it's not immediately obvious how breathing can help us lose weight. If we think in chemistry terms, breathing is no more than the exchange of oxygen (O₂) and carbon dioxide (CO₂) with the environment. Can you already see where the weight loss occurs? Exactly! One gas is heavier than the other.

Oxygen has an atomic mass of 16 au and carbon has 12 au per atom. This means that when we inhale we take 32 au per molecule of O₂ and then exhale 44 au back in the form of carbon dioxide. The difference is 12 au per molecule, which is not much, but taking into account how many molecules there are in a breath, and how many breaths we take every night, it all adds up. Definitely an unexpected and very interesting explanation for this surprising effect.

Another important thing to realize is that this process keeps happening as long as we are alive. The reason we don't just become lighter from breathing a couple of days is that this effect is too small when we compare it the food and liquid we eat and drink every day. Though noticeable in strict conditions (such as over a good night's sleep) the effect is overpowered by the more than 3 kg that we normally introduce in our body in the form of water or food.

Unfortunately, this is not a good way to lose weight, we still need to replenish our burned calories for a healthy lifestyle and exercise periodically not only to prevent heart diseases but also for keeping our weight in check. However, this effect brings to light something very important, that we should never forget. The number one requirement