Calculator for video timings v. 1.9

Copyright Tomi Engdahl 1998-2006

NOTE1: You need a web broser that supports JavaScript to run this application. Most modern web browsers support JavaScript, but some users have this disable on their system for security reasons. This software hould work with following or newer browsers: Netscape 2.0, IE3 browser (with JavaScipt/Jscript turned to), Mozilla Firefox 1.0 and Opera. This version has been tested to work with IE6 and Mozilla Firefox 1.0.

NOTE2: There is no guarantee that the results you get from this from are correct. Use this at your own risk. If you find errors in this page please e-mail me with a good description what is wrong.

1. Select the setting where you start

There are two ways to select the settings. You can freely use either one of them. For most applications selecting from the readily available screen modes is the best option.

Select the screen mode timings:

Or give Xfree86 modeline to import:

2. Look at graphics card settings and modify them

General parameters

Pixel clock frequency MHz


Horizontal timing parameters

Resolution pixels
Front porch pixels
Sync pulse pixels, polarity *
Back porch pixels

Vertical timing parameters

Resolution lines
Front porch lines
Sync pulse lines, polarity *
Back porch lines

* For sync polarities 0 = NEGATIVE SYNC and 1 = POSITIVE SYNC

Move picture:

3. Start calculation

Press when you want to get the results.

4. View calculated results

Numerical results

Horizontal sync frequency is kHz.
Vertical sync frequency is Hz.
Field rate is Hz.

Horizontal sync pulse length is microseconds.
Vertical sync pulse length is microseconds.

Horizontal total is pixels and vertical total is lines.

If you want to test other values then fill in new values to form on step 2 and press calculate again.

Configuration files

NOTE: The following configuration files are calculated from the data above. There no guaantee that the calculated configuration files work on your system. Use the configuration files at your own risk. In some unfortunate cases it is possible that you damage your monitor or mess up your graphics card driver settings.

Xfree86 modeline (to be included to XConfig file):

Matrox Windows driver custom monitor settings (to be included to MGA.MON file):

Windows95 monitor.inf file modeline:

Note: Windows monitor .INF file contains only the screen refresh rate and sync polarity information. It does not contain screen position information.

Some instructions and notes

This page lists the most commonly used resolutions and refresh rates that you can modify. You can modify all the parameters you want. The you can use any combination of H and V resolution (ok, number of pixels) and refresh rate that are supported by your operating system, graphics card and your monitor. Windows is pretty much limited on what resolutions it can use, but with X you can pratcially use almost any any combination of H and V resolution (ok, number of pixels) and the limit is the card (clock and RAM) and the monitor capabilities.

Note 1: Actual vertical and horizontal refresh rated depend on the screen resolution, video clock rate and some other numbers (porch and sync pulses).

Note 2: The horizontal timing parameters must be normally to be multiple of 8 because this is the resolution which stadard VGA cards operate in those timings and same applies to most of SVGA cards also.

Note 3: Screen mode settings do not set the sync signal polarity because the needed sync signal polarity depends on the monitor and screen mode used. If you do not know what polarity is needed try first to check both negative. Sync signal polarity settings do not affect the timing calculations. Sync signal polarities affect only to the generated configuration files.

Note 4: Moving picture the picture to the extreme positions may result unstable picture on the monitor.

Note 5: The screen mode settings are general settings usually targeted for 8 bpp (256 colors) modes. On some higher color modes some graphics cards seem to have some limitations what horizontal resolution settings can be (a multiple of 32 pixels in some cards). This might cause that all settings might not work with all card in all modes. Because of large variety of graphics cards and operating systems, not all combinations of things could have been tested. If something does not work for you, then try some other settings or try to modify the mode to suit better to your card (if you know what to correct).

Note 6: In interlaced modes the vertical sync timing parameters are per interlaced field. Interlace draws only half of the screen each refresh, doubling the effective refresh rate. Interlaced modes are well known for their high flicker, but a 60Hz interlaced mode looks much better than a 30Hz non-interlaced mode.

Note 7: Horizontal Sync Time typically varies form 3.5 to 4.0 microseconds in normal PC monitor applications. Vertical Sync Time usually varies from 50 to 300 microseconds.

Note 8: I can't have all the screen modes in the world in my calculator (don't e-mail me to ask for details of modes not listed here, I don't have a secret repositiory of all the screen modes). To be able to fullfill the need od people that need something else that not already offred here, there is option to modify the screen mode settings (the actual reason to built this calculator was to make modifying screen modes easy). Generally you take the nearest matching mode and then modify it to match your needs. For example if you need slightly higher or lower refresh rate that is offered by the ready made settings, just try to modify the pixel clock frequency accordingly to make the mode to refresh at the rate you want. If the resolution is not exacly right, you can make slight modifications to vertical and horizontal resolution fields.

Note 9: If you need a screen mode not listed here or are in doubt what is suitable for your monitor specifications, take a look at the screen mode calculator at It can generate Xfree68 modelines with different kind of user interface, you just need to input few details of your monitor and resolution you eant. Those modelines can be imported to this calculator, and modify them here if you feel a need to do so.

Note 10: If you have problems with this newest calculator version, try some older version: v1.6 or v1.5

Note 11: If you want to have on off-line calculator like this on you computer, just simply save this web page to your computer. It will work nicely locally on your computer through you web browser just like this on-line version. You do not need any Internet connection to use this locally saved copy of this calculator.

Note 12: The Xfree86 modeline importer in this calcualtor version is not foolproof and might not import all modelines correctly. So check after modeline import that your data got imported correctly and do corrections to it if needed. According the comments I have received the modeline importer does not handle interlaced screen modes correctly.

Tomi Engdahl <>

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