Refresh rate
Refresh rate measures how often a raster display updates its image.
Refresh rate—also called vertical refresh rate, vertical scan rate, or vertical frequency—measures how many times per second a raster display device draws a new image. The term comes from cathode-ray tube (CRT) technology. It is not the same as frame rate, which counts how many images a computer or video source generates each second. On CRTs, a higher refresh rate means less flicker and less eye strain. On liquid-crystal displays (LCDs), the refresh rate only sets the upper limit for how often the image can change. Some displays, like vector displays, don’t have a fixed refresh rate because they don’t scan the whole screen; instead, they draw only the lines that make up the image, so their update speed depends on image complexity. In software or telemetry contexts, “refresh rate” sometimes refers to how often a data value is updated from an external source, such as a shared spreadsheet or hardware feed.
Different display technologies handle refresh differently. In a CRT, the phosphors that create the image fade quickly, so the screen must be redrawn constantly. The vertical scan rate is how many times per second the electron beam returns to the top-left corner to start a new frame. This rate is set by the video controller’s vertical blanking signal and is limited by the monitor’s maximum horizontal scan rate. You can calculate it by dividing the horizontal scan frequency by the number of horizontal lines, then multiplying by 1.05 to account for the beam’s return time. For example, a monitor with a 96 kHz horizontal scan rate at 1280×1024 resolution gives about 89 Hz. In early video games, the only time the system could perform calculations was during the vertical blanking interval—when the beam was moving back to the top and no image was drawn. Even in modern games, updating the video buffer outside this interval can cause flicker or screen tearing.
LCDs work differently. Their pixels hold their state as long as power is on, so there’s no inherent flicker at any refresh rate. But the refresh rate still caps the highest frame rate the display can show. Even though LCDs don’t blank the screen, they still have a vertical blanking interval—a period each cycle when the screen isn’t being updated—during which the host system can safely update its frame buffer. Vsync uses this interval to prevent tearing by rendering the whole image at once.
- Crt refresh calculation
- horizontal scan rate ÷ (number of horizontal lines × 1.05)
- Example crt refresh
- 96 kHz horizontal scan at 1280×1024 yields ≈ 89 Hz
- First 144hz display year
- 2012
- Asus vg248qe release year
- 2013
- Asus rog swift pg258q 240hz release year
- 2017
- Asus rog swift pg259qn 360hz release yea
- 2020
- Asus rog swift pro pg248qp 540hz release
- 2023
- Lg ultragear 25g590b 1000hz announcement
- May 2026
Lore & Background
In cathode-ray tubes, the vertical scan rate is the number of times per second that the electron beam returns to the upper left corner of the screen to begin drawing a new frame. It is controlled by the vertical blanking signal generated by the video controller and is partially limited by the monitor's maximum horizontal scan rate. The refresh rate can be calculated from the horizontal scan rate by dividing the scanning frequency by the number of horizontal lines, plus a 1.05x multiplier for beam return time. CRT refresh rates have historically been an important factor in video game programming; in early videogame systems, the only time available for computation was during the vertical blanking interval. Even in modern games, it is important to avoid altering the computer's video buffer except during the vertical retrace to prevent flickering graphics or screen tearing.
Unlike CRTs, the pixels of liquid-crystal displays retain their state for as long as power is provided, so there is no intrinsic flicker regardless of refresh rate. However, the refresh rate still determines the highest frame rate that can be displayed, and the vertical blanking interval remains a period when the screen is not being updated. Some displays support variable refresh rate (VRR), the ability to change their refresh rate on-the-fly, which can save power or lower input latency. FreeSync and G-Sync are implementations of VRR seen in AMD and Nvidia's graphics cards, respectively.
Beginning in the 2010s, competitive video gaming prompted manufacturers to develop displays with higher refresh rates than the standard 60 Hz. The first 144 Hz displays appeared in 2012, with the 24-inch ASUS VG248QE released in 2013. At 144 Hz, frame persistence reduced to approximately 6.9 milliseconds, compared to 16.7 milliseconds at 60 Hz. Progression continued through the 2010s: 240 Hz monitors appeared in 2017, 360 Hz in 2020, and 540 Hz in 2023. In May 2026, LG Electronics announced the UltraGear 25G590B, marketed as the world's first gaming monitor with a native 1000 Hz refresh rate at full HD resolution.
Reader's Guide
Refresh rate has been a defining characteristic of display technology since the era of cathode-ray tubes, where it directly affected visual comfort by reducing flicker and eye strain. On smaller CRT monitors up to about 15 inches, few people notice discomfort between 60–72 Hz, while on larger CRT monitors of 17 inches or more, most people experience mild discomfort unless the refresh is set to 72 Hz or higher. A rate of 100 Hz is comfortable at almost any size. This does not apply to LCD monitors, where the closest equivalent to refresh rate is frame rate, often locked at 60 fps, but the backlight typically operates at around a minimum of 200 Hz, preventing CRT-like flicker.
Different operating systems set default refresh rates differently. Microsoft Windows 95 and Windows 98 set the refresh rate to the highest rate they believe the display supports, while Windows NT-based operating systems and their descendants, including Windows 11, set the default to a conservative rate, usually 60 Hz. Most Linux distributions follow the same behavior, but some dynamically set a default based on the monitor's refresh rate. macOS is normally locked to 60 Hz with exceptions like later MacBook Pro models. Old monitors could be damaged if a user set the video card to a refresh rate higher than the highest rate supported by the monitor.
In stereo 3D displays using LCD shutter glasses, the effective refresh rate is halved because each eye needs a separate picture, so a display capable of at least 120 Hz is usually recommended. Higher refresh rates result in greater image stability. For LCD monitors, pixel brightness changes are much slower than CRT or plasma phosphors, and asymmetric pixel response time can cause blurry smearing with 3D shutter glasses.
Did You Know?
- On CRT displays, higher refresh rates produce less flickering, thereby reducing eye strain.
- The refresh rate can be calculated from the horizontal scan rate by dividing by the number of horizontal lines times a 1.05 multiplier.
- The ASUS ROG Swift Pro PG248QP reached 540 Hz through an overclock of its native 360 Hz 'Esports TN' panel.
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