What is refresh rate?

Smearing when watching short videos, lag in gaming, eye strain from looking at the screen for extended periods—have you ever considered that these issues affecting user experience may all be related to a key parameter: refresh rate. This number, measured in Hz, hides the core logic of screen display, yet many people consider it a “dispensable parameter.”

Ⅰ. What is refresh rate?

The core definition of refresh rate is simple: the number of times a screen can redraw an image per second, measured in Hertz (Hz). 1Hz means the screen refreshes once per second, while 60Hz means 60 times per second. The higher the number, the more frequent the image updates.

It’s important to note that the refresh rate we usually refer to is the vertical refresh rate (field frequency), which is the number of complete frames per second. The corresponding parameter is the horizontal refresh rate (line frequency), which refers to the number of horizontal lines scanned by the electron gun per second. However, for the average user, the vertical refresh rate is the most critical parameter affecting the user experience.

Ⅱ. How to calculate the refresh rate? 

Intuitive conversion from 10Hz to 240Hz The key to understanding the refresh rate is to master its inverse relationship with the refresh time, which is also the core logic for judging the smoothness of the screen.

1. Core calculation formula:

Refresh time (the interval between single screen updates) = 1 ÷ refresh rate (Hz)

The essence of this formula is to convert “number of refreshes per second” into “the time interval between each refresh”. In terms of unit conversion, 1 second = 1000 milliseconds (ms), so the calculation result is usually converted to milliseconds for easier perception.

2. Actual conversion of common refresh rates

Let’s take the typical refresh rate in different scenarios as an example to calculate its corresponding refresh time:

(1) 10Hz refresh rate: 1÷10=0.1 second = 100 milliseconds. This type of refresh rate is commonly found in electronic ink screens (such as Kindle). Because e-books are mainly static displays and do not require high-frequency updates, low refresh rates can significantly save power.

(2) 60Hz refresh rate: 1÷60≈0.0167 seconds = 16.7 milliseconds. This is the most basic refresh rate standard currently, widely used in ordinary mobile phones, office monitors and TVs, and can meet daily needs such as web browsing and video playback.

(3) 120Hz refresh rate: 1÷120≈0.0083 seconds = 8.3 milliseconds. High-end mobile phones and mid-to-high-end monitors often use this specification. The smoothness of scrolling the screen and watching high-frame-rate videos is significantly improved compared to 60Hz.

(4) 144Hz refresh rate: 1÷144≈0.0069 seconds = 6.9 milliseconds. This is the mainstream configuration for e-sports monitors. In competitive games such as CS2 and League of Legends, it can make fast-moving images clearer and reduce operation delays.

(5) 240Hz refresh rate: 1÷240≈0.0042 seconds = 4.2 milliseconds. This is the configuration of professional esports equipment, which has extremely high hardware performance requirements and is primarily targeted at professional players and hardcore gamers.

This data clearly shows that the higher the refresh rate, the shorter the interval between refreshes, and the faster the image updates. When the refresh rate is shorter than the human eye’s visual retention time (approximately 100 milliseconds), continuous images create a smooth motion effect, similar to the principle that creates dynamic images in movies at 24 frames per second.

3. Hardware Limitations of Refresh Rate

It’s important to note that the maximum refresh rate a screen can achieve isn’t arbitrarily set; it’s limited by hardware bandwidth. A monitor’s bandwidth determines how quickly it can process image signals. The larger the screen size and the higher the resolution, the greater the bandwidth required. For example, a 17-inch CRT monitor needs at least 100MHz of bandwidth to achieve an 85Hz refresh rate at a 1024×768 resolution; a 21-inch monitor would require over 300MHz of bandwidth to meet the same requirements.

For modern devices, in addition to the monitor itself, the performance of the graphics card also affects the actual refresh rate. If the graphics card can’t output a sufficient frame rate, even if the monitor supports a high refresh rate, performance will be wasted. For example, using an entry-level graphics card with a 240Hz monitor to play AAA games may result in less smooth and stable graphics than on a 60Hz monitor.

Ⅲ.Refresh rate ≠ frame rate? Don’t confuse these two key parameters anymore. 

Many people confuse refresh rate and frame rate (FPS). In fact, the two are completely different concepts, but they are closely related. Simply put: frame rate is “production speed” and refresh rate is “display speed”. 

1. The core difference between the two 

1. Frame rate (FPS): refers to the number of images generated by the graphics card or host per second, and the unit is frames per second. For example, “120FPS” displayed in the game means that the graphics card generates 120 frames per second. The frame rate mainly depends on the hardware performance of the CPU, graphics card, etc.
2.  Refresh rate (Hz): refers to the number of images displayed on the screen per second, which is determined by the display hardware. For example, a 60Hz monitor can display a maximum of 60 frames per second. Even if the graphics card generates 120 frames, the extra frames cannot be displayed. 
3. To understand it with an analogy: frame rate is equivalent to the number of loaves of bread produced per second by a factory, and refresh rate is equivalent to the number of loaves of bread sold per second by a convenience store. If the factory produces 120 loaves per second (120FPS), but the convenience store can only sell 60 loaves per second (60Hz), then 60 loaves per second will be wasted (invalid frames); if the factory only produces 30 loaves per second (30FPS), but the convenience store can sell 60 loaves per second (60Hz), then there will be 30 empty slots per second (the same frame is displayed repeatedly), causing the screen to freeze.

2. The importance of matching the two

(1) Only when the frame rate and refresh rate are basically matched can the best visual experience be obtained:

(2) Frame rate ≥ refresh rate: For example, 144FPS with a 144Hz monitor can fully utilize the high refresh rate advantage, and the picture is smooth and without waste. However, a frame rate that is too high (such as 500FPS with a 240Hz monitor) is meaningless and there is performance redundancy.

(3) Frame rate < refresh rate: For example, when 60FPS is paired with a 120Hz monitor, the screen will be repeated. Although there will be no noticeable lag, the smoothness will not be as natural as when the two are matched. (4) Frame rate is much lower than the refresh rate: For example, when 30FPS is paired with a 144Hz monitor, there will be obvious screen lag and ghosting, especially in gaming scenes, which will affect the accuracy of operation. To solve the problem of mismatch between the two, monitor manufacturers have introduced adaptive synchronization technology, such as NVIDIA’s G-SYNC and AMD’s FreeSync, which allows the monitor refresh rate to automatically follow the frame rate changes to avoid screen tearing and lag.

Conclusion

Refresh rate isn’t about “higher is better,” but rather “more appropriate is better.” It’s evolved from a “must-have” for flicker prevention in the CRT era to a core parameter that influences the user experience today, driven by the continuous advancement of display technology. Understanding the definition and calculation of refresh rate, as well as its relationship to frame rate, can help us choose electronic devices more rationally, avoiding wasting budget by blindly pursuing high refresh rates or sacrificing the user experience by ignoring performance parameters. Ultimately, the best option is the one that suits you best.

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