How Does a Smartwatch Count Calories?

For calorie tracking, smartwatches have become a part of our daily routine. But how do they function, and how accurate are they? 

Electronic wearables have flourished in recent years, with smartwatches and fitness trackers being the most popular. You’re undoubtedly carrying one right now, or at least know someone who does. Smartwatches may do various things, but for many people, the most important aspect is how they can help us achieve our fitness objectives. 

Their ability to monitor our activities and calculate how many calories we have expended is impressive. Have you ever sat back and pondered how your smartwatch calculates the number of calories you consume? It is not as straightforward a process as it may look at first.

How Do Smartwatches Measure Calories?

how a smartwatch can track calories

Now that we’ve discussed why it’s essential to track your calorie intake let’s see how smartwatches do it. When you set up an account for your wristwatch or activity tracker, you’ll be asked to provide basic information. 

It generally comprises the following: 

  • Height 
  • Weight 
  • Age 
  • Sex 
  • Usual activity level

The business that makes your smartwatch isn’t simply gathering data for its sake. It uses it to compute your metabolic rate during rest (BMR). 

How Does it Work?

Keep in mind that your body expends energy to function. Everything is absolute. Breathing, digesting, and blinking are all examples of this. So you’re burning calories even if you’re sitting on your sofa watching TV. 

The quantity of calories you burn while you aren’t moving about is very variable, depending on the variables you enter into your account. Men, for example, have a greater BMR than women, and bigger persons have a higher BMR than those who are smaller. 

Your wristwatch can compute your active calorie expenditure once it gets your BMR. 

It’s the energy you expend when you’re sitting around doing nothing. It might be anything from going up the stairs to doing housekeeping to participating in a high-intensity interval training session. 

Accelerometers And Heart Rate Monitoring In Smartwatches

smartwatch accelerometer and heart rate

Smartwatches typically employ the accelerometer integrated into the device to track your movements (this is also how they count your steps). They’ll also check your heart rate using a heart rate monitor to measure how rapidly it’s thumping (the faster the heart rate, the more calories you burn on average). 

The firm’s actual formula differs and is often maintained as a guarded secret.

Fitbit, for example, claims to create its calorie calculation algorithm using AI, machine learning, and a database full of biometric data from a broad spectrum of individuals. Similarly, Apple did research utilizing the metabolic profiles of 10,000 individuals. 

Apple used accurate metabolic gas measurements to determine the research participants’ calorie consumption, then connected them with their heart rate and activity data. Their watches are then programmed to compute calorie burn as precisely as possible using this information.

What Are Calories?

A calorie is a measuring unit. It is a unit of energy in particular. Over the past century, several ways have been used to define a calorie. Still, a calorie is defined as the amount of heat required to increase the temperature of a gram of water from 14.5 to 15.5 degrees Celsius. 

It’s a “little calorie” and not the same as the calories shown on product labels. They are frequently called kilocalories since they contain 1,000 of these little calories. Calories, in any event, are a unit of measurement for energy. 

Calories are found in every bite of food you consume, and every area of your body uses them to operate. As a result, you’re constantly transferring energy from your meals to your body. 

Why Are Calories Necessary For Weight Loss?

Smart Watch calories burned accuracy

The emphasis on calories in weight reduction is because extra calories cause weight growth. 

When you consume more calories than you expend, the excess energy must be expended. 

And your body efficiently stores it as fat to be utilized later. 

When you eat too many calories daily, you may gain weight. So, if you’re attempting to lose weight, you’ll need to record how many calories you consume through food and how many calories you expend via exercise. 

A calorie tracker may help you keep track of how many calories you consume, but a wristwatch can also help you track how many calories you burn.

How Accurate Are Smartwatch Calorie Data?

Your fitness band or standalone smartwatch’s calorie burn estimate will always be an estimate. 

Because smartwatches never actually monitor calorie burn, they can’t be 100 percent accurate in estimating how many calories you burnt during your exercise. 

They can only guess based on the data from the accelerometer and heart rate monitor and their algorithm. Smartwatches don’t normally consider certain aspects that might affect how many calories you burn. 

Persons with a greater muscular tone, for example, have a faster metabolic rate and burn more calories when they are active than people with fewer muscles. When calculating the number of calories you’ve consumed, most organizations don’t consider this yet. 

The excellent thing is that, in most circumstances, precise accuracy shouldn’t be a major concern. The actual amount that appears on your screen isn’t always the essential piece of calorie data. 

Comparing the number of calories burnt from one day to the next and from one activity to the next is crucial. This might assist you in learning about how to improve your fitness or lose weight by burning calories and keeping you encouraged to be as active as possible. It’s also intriguing!


One of the great benefits of smartwatches and activity trackers is monitoring how many calories you burn in a day or how many you burn when doing certain activities. The precise quantity of calories consumed is calculated by each company using its methods. 

They all depend on data from their accelerometers and heart rate monitors to make that estimate. While this will never be completely precise, it may give you a good sense of what activities are good for burning calories and keep a record of how active you are daily.

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