How Smartwatches Of Fitness Bands Measure Heart Rate

Photo by Luke Chesser on Unsplash

The smartwatch and fitness bands are the most useful gadgets nowadays, they help us measure and analyze our daily activities such as Heart rate, sleep monitoring, steps, distance, calories burned and miles walked. Thanks to this latest technology it helps us track our health activities. 

But for Heart rate monitoring, most people are worried about How smartwatches and fitness bands measure heart rate. Or whether they are accurate.

If you have the same question in your mind, then you are in the right place. Today in this article I am going to discuss how smartwatches and fitness bands measure Heart rate.  

So, without any further delay, let’s get started!

Before we dive into the article, we need to understand what is Heart rate? 

Heart rate is the number of times your heart beats in one minute. It depends on your activities. For example, when you are resting, your heart beats slower, or when you exercise, your heart beats faster.

As you grow older, changes in heart rate and regularity can change, which can mean heart disease or other conditions that need treatment.

How do you monitor your pulse?


  1. Just you need to put your fingers gently on your wrist, similar to the one shown in the image.
  1. If you feel your pulse, start counting the beats in the following 15 seconds and multiply the number of beats by 4. 

How do smartwatches and fitness bands measure heart rate?

Most of the smartwatches and fitness bands use photoplethysmography, or PPG sensors and green LED lights on the device which work together to track the heart rate. Both components in the device play a vital role in tracking the heart rate. 

When the LED light on the device transmits the green lights into the red blood, our red blood absorbs the green lights and reflects the red lights while the PPG sensor tracks the number of heartbeats or heart rate per minute.

Here is a simple way to understand how PPG sensors work. 

Photoplethysmography (PPG) is a technology used for detecting the volume of blood flow in the pulse. When the heartbeats, more blood flows in the wrist, and the Photoplethysmography (PPG) sensor easily detects the heartbeats or heart rate.

In addition, ECG (electrocardiogram) sensors have been used to measure heart rate and rhythm, but the ECG technology is relatively slightly heavier and cannot be used to detect heart rate when the body is moving.

Four key components of PPG technology

The PPG technology uses the following four key components for tracking the heart rate

Optical emitter

The optical emitter comprises two LED lights that are conscious to transmit light waves to the skin, bones, and tissues of the wrist. It uses different wavelengths depending on the difference in skin tone, thickness, and shape of the wearer, and various wavelengths allow interaction with different levels of skin and tissues. 


Measure your movement. It then integrates the collected data with the DSP signal and together acts as input data in the PPG algorithm.

Digital Signal Processor (DSP)

This component can capture the refracted light from the user and convert these signals into the binary language (1s and 0s) and then into heart rate data.


Algorithms basically act on the inputs of DSP and accelerometers to collect acceptable heart rate data. Depending on the capabilities of the device, it can calculate VO2, calories burned, heart rate variable, R-R interval, blood metabolite concentration, blood oxygen level, and even blood pressure.

Is your smartwatch or fitness band accurate? 

As compared to the professional medical equipment, the smartwatches and fitness bands are not accurate, they are pretty close to measuring the heart rate, but not like the professional medical equipment. So, if you are considering the smartwatch and fitness bands for critical heart rate monitoring, then this is not a good move for you. 

Although smartwatches and fitness bands are nearly accurate as compared to professional medical equipment, it does not mean that you need to use these kinds of devices for critical heart rate monitoring. Instead, you can use this type of device for features and activity tracking.

I hope this piece of information is helping you to understand How smartwatches and fitness bands measure Heart rate.

Thank you for your time, and have a great day!