首先，解釋一下這三個概念
行頻(Horizontal Scanning Frequency): 又稱為“水平掃描頻率”，是指每秒在屏幕上從左到右掃描的行數，單位是kHz；如果行頻為110kHz，表示每秒掃描110000行。
場頻(Vertical Scanning Frequency): 又稱為“垂直掃描頻率”，是指每秒鍾屏幕刷新的次數，單位是Hz；CRT時代，電子是從左到右，送上到下逐行掃描的，所以，掃描完一列就相當於掃描完整個屏幕，即刷新整個屏幕，故又稱為“刷新率”，沿用至今。
顯示器垂直分辨率: 顯示器垂直方向上可顯示的像素數目
顯示器水平分辨率: 顯示器水平方向上可顯示的像素數目
這就很好理解公式了:
行頻 = 場頻 * 垂直分辨率 * K(一個常數)
即“每秒掃描的行數”等於“每秒刷新的次數”乘以“每次刷新掃描的行數”再乘以“一個性能常數”
那么，為什么會有一個常數？答案也很簡單，由於每次掃描到最后一個像素后，下次又要重定位到左上角，存在一個性能上的消耗，所以“行頻”會比“場頻*垂直分辨率”大，即K一般大於1。
摘要：
Factors in determining refresh rates
A refresh rate is dependent upon a monitor's horizontal scanning frequency and the number of horizontal lines displayed.The horizontal scanning frequency is the number of times the electron beam sweeps one line and returns to the beginning of the next in one second. Horizontal scanning frequency is measured in kilohertz (kHz).
A monitor with a horizontal scanning frequency of 110 kHz means 110,000 lines are scanned per second. The number of horizontal lines on the screen depends upon the monitor's resolution. If a monitor is set to a resolution of 1024 x 768 then there are 768 horizontal lines (1024 is the number of pixels on one line).
For a monitor set to a 1280 x 1024 resolution, there are 1024 horizontal lines. Additionally, the time it takes for the electron beam to return to the top of the screen and begin scanning again must be taken into account. This is roughly 5% of the time it takes to scan the entire screen. Therefore, the total is multiplied by 0.95 to calculate the maximum refresh rate.
vertical scan frequency called "refresh rate," it is the number of times an entire CRT screen wasrefreshed, or redrawn, per second. Measured in Hertz, display systems typically ranged from 56 Hz to over 100, but at least70 was recommended to help prevent eyestrain.
The earliest CRTs were unable to support both the highest resolution along with a high refresh rate; however, later CRTsprovided adequate rates at all resolutions. Vertical scan frequency is not an issue with LCD displays because they do notuse phosphors that have to be continuously energized. However, the data from the frame buffer is continuously sent to theLCD panel in order to display animation and video. Thus, the flat panel does have a maximum refresh rate to support motion,but not to refresh static images.
參考：
How are refresh rates calculated? And What is the Importance of Refresh Rates