Screen tearing when scrolling through short videos, lag when playing games, and eye strain after prolonged screen time—have you ever considered that these issues affecting user experience might all be related to a key parameter: refresh rate? This number, measured in "Hz," holds the core logic of screen display, yet many people consider it a "dispensable parameter." This article will delve into the definition, calculation method, and difference between refresh rate and frame rate to help you fully understand this important concept.

I. What is Refresh Rate?

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

It's important to note that the refresh rate we usually refer to is the vertical refresh rate (vertical refresh rate), which is the number of times the image is fully drawn per second. There is also a horizontal refresh rate (horizontal refresh rate), which refers to the number of lines the electron gun scans horizontally per second. However, for ordinary users, the vertical refresh rate is the key parameter affecting the user experience.

II. Refresh Rate Calculation: An Intuitive Conversion from 10Hz to 240Hz

The key to understanding refresh rate lies in grasping its reciprocal relationship with refresh time, which is also the core logic for judging screen smoothness.

Core Calculation Formula: Refresh Time (interval between single screen updates) = 1 ÷ Refresh Rate (Hz)

This formula essentially converts "refreshes per second" into "the time interval between each refresh." For unit conversion, 1 second = 1000 milliseconds (ms), so the calculation result is usually converted to milliseconds for easier perception.

Practical Conversion of Common Refresh Rates:

We calculate the corresponding refresh time using typical refresh rates in different scenarios as examples:

10Hz Refresh Rate: 1 ÷ 10 = 0.1 seconds = 100 milliseconds. This type of refresh rate is common in e-ink screens (such as Kindle) because e-books are mainly static displays and do not require high-frequency updates; a low refresh rate can significantly save power.

60Hz Refresh Rate: 1 ÷ 60 ≈ 0.0167 seconds = 16.7 milliseconds. This is currently the most basic refresh rate standard, widely used in ordinary mobile phones, office monitors, and TVs, meeting the needs of daily web browsing and video playback.

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, offering a significantly smoother experience when scrolling and watching high frame rate videos compared to 60Hz.

144Hz Refresh Rate: 1 ÷ 144 ≈ 0.0069 seconds = 6.9 milliseconds. A mainstream configuration for gaming monitors, it makes fast-moving scenes clearer and reduces operation lag in competitive games such as *CS2* and *League of Legends*.

240Hz refresh rate: 1 ÷ 240 ≈ 0.0042 seconds = 4.2 milliseconds. This is a configuration for professional esports equipment, requiring extremely high hardware performance and primarily targeting professional players and hardcore gamers.

These data clearly show that a higher refresh rate means a shorter time interval between refreshes, resulting in faster image updates. When the refresh time is shorter than the human eye's visual persistence (approximately 100 milliseconds), continuous images create a smooth dynamic effect, consistent with the principle behind movies using 24 frames per second (fps) to create motion.

Hardware Limitations of Refresh Rate
It's important to note that the maximum refresh rate a screen can achieve is not arbitrarily set but is limited by hardware bandwidth. The monitor's bandwidth determines its image signal processing speed; larger screen sizes and higher resolutions require more bandwidth. For example, a 17-inch CRT monitor needs at least 100MHz of bandwidth to achieve an 85Hz refresh rate at 1024×768 resolution, while a 21-inch monitor requires over 300MHz of bandwidth to meet the same requirements.

For modern devices, besides the monitor itself, graphics card performance also affects the actual refresh rate performance. If the graphics card cannot output a sufficient frame rate, even if the monitor supports a high refresh rate, there will be "performance waste"—for example, playing AAA games with an entry-level graphics card and a 240Hz monitor might result in less smooth gameplay than with a 60Hz monitor.

III. Refresh Rate ≠ Frame Rate? Don't Confuse These Two Key Parameters

Many people confuse refresh rate with frame rate (FPS), but they are completely different concepts, yet closely related. Simply put: **Frame rate is the "production speed," while refresh rate is the "display speed."**

The Core Differences:
Frame Rate (FPS): Refers to the number of images generated per second by the graphics card or host, measured in frames per second. For example, "120 FPS" in a game means the graphics card generates 120 frames per second. The frame rate mainly depends on the performance of hardware such as the CPU and graphics card.

Refresh Rate (Hz): Refers to the number of images displayed on the screen per second, determined by the monitor hardware. For example, a 60Hz monitor can only display a maximum of 60 frames per second. Even if the graphics card generates 120 frames, the extra frames cannot be displayed.

To understand this analogy: frame rate is like the number of loaves of bread a factory produces per second, while refresh rate is like the number of loaves of bread a convenience store can sell per second. If the factory produces 120 loaves/second (120FPS), but the convenience store can only sell 60 loaves/second (60Hz), then 60 loaves of bread per second will be wasted (invalid frames); if the factory only produces 30 loaves/second (30FPS), but the convenience store can sell 60 loaves/second (60Hz), then 30 slots per second will be empty (repeatedly displaying the same frame), causing stuttering.

The Importance of Matching Frame Rate and Refresh Rate Only when frame rate and refresh rate are roughly matched can the best visual experience be achieved:
Frame Rate ≥ Refresh Rate: For example, 144FPS paired with a 144Hz monitor can fully utilize the advantages of a high refresh rate, resulting in smooth and wasteless visuals. However, excessively high frame rates (such as 500 FPS on a 240Hz monitor) are not very meaningful and create performance redundancy.

Frame rate < refresh rate: For example, 60 FPS on a 120Hz monitor will result in repeated image display. While there won't be noticeable stuttering, the smoothness is not as natural as when the two are matched.

Frame rate significantly lower than refresh rate: For example, 30 FPS on a 144Hz monitor will result in noticeable stuttering and ghosting, especially affecting accuracy in gaming scenarios.

To solve the problem of mismatch, monitor manufacturers have introduced adaptive synchronization technologies, such as NVIDIA's G-SYNC and AMD's FreeSync, which allow the monitor's refresh rate to automatically follow the frame rate, avoiding screen tearing and stuttering.

Conclusion: Higher refresh rate is not always better; rather, "the more suitable, the better." It has evolved from a "flicker-free necessity" in the CRT era to a "core parameter" affecting the user experience today, thanks to the continuous advancement of display technology. Understanding the definition and calculation method of refresh rate, as well as its relationship with frame rate, can help us make more rational choices about electronic devices—neither blindly pursuing high refresh rates and wasting our budget, nor sacrificing our experience by ignoring parameters. After all, what suits you best is the best choice.