Wednesday, June 24, 2009

How to calculate dot pitch

Dot Pitch is the measure of the distance between each adjoining pixel on a color computer monitor (including LCD monitors), expressed in millimeters (mm). The lower the dot pitch the sharper the displayed image. Typically color monitors come with a dot pitch of 0.3 mm or lower.

Dot Pitch is related to resolution because resolution is a measure of the number of pixels horizontally and vertically. Given this relationship we can calculate the dot pitch of any monitor if we know the horizontal resolution, vertical resolution, and the diagonal distance. Technically, if we new vertical and horizontal measure in inches for example, we could do the same thing and get a more accurate measure of dot pitch. However, all marketing and technical specs use the horizontal dot pitch.

With a little math and conversion of units you can easily calculate the dot pitch yourself.

Let’s take the example of a monitor that is 1280 pixels horizontally by 1024 pixels vertically and has a viewable display (make sure you use the viewable measurement, not the advertised one since they differ slightly sometimes) of 20 inches.

Below is visual of the information we know. You’ll notice that we have a difference in the units here. We have pixels and inches. We do need to do some calculations to figure out what the 20 inches is in pixels.


To calculate the diagonal in pixels we need to go back to our grade school math class. We can think of the problem as math problem where we have a right triangle and are solving for the hypotenuse (the diagonal). Below is a visual of the problem.


We need to solve for d. To do that we use the formula

d*d = x*x + y*y

We need to solve for d which means

d = square root (x*x + y*y)

For our example:  d = square root (1280 * 1280 + 1024 * 1024)

d = 1639.2 pixels

Now we know the diagonal in inches and pixels. This means we can calculate the ratio between them which is known as pixels per inch (ppi). This can be calculate very simply by dividing pixels by inches.

ppi = pixels / inches

In our example: ppi = 1639.2 / 20 = 81.96 pixels per inch.

This is a measure of dot pitch, but it is not really what marketing and technical specs will use. They use millimeters since they are smaller units of measure and more appropriate for small things like pixels.

To make our calculation compatible with marketing and technical specs we need to convert our answer to pixels per millimeter (dot pitch). It is a known conversion factor that 1 in is equal to 25.4 mm. Here is the formula to convert our answer to pixels to millimeter.

dot pitch = 25.4 / ppi

For our example: dot pitch = 25.4 / 81.96 = .31 pixels per mm (which is commonly known as dot pitch)

If you don’t want to do the math yourself, you can just use the JavaScript function below.

function calcDotPitch(hPixels, vPixels, diagonal)
var d = Math.sqrt(hPixels * hPixels + vPixels * vPixels);
var ppi = d/diagonal;
var dotPitch = 25.4 / ppi;
return dotPitch;
alert(calcDotPitch(1280, 1024, 20));


Anonymous said...

"For our example: dot pitch = 25.4 / 81.96 = .31 pixels per mm (which is commonly known as dot pitch)"


U got the units wrong. A dot pitch of .31 means each pixel is .31mm across ie. 31mm per pixel.

Jan Tore Eliassen said...

Hi Brent V...
Very nice read.
Very informative.
You should have pointed out that it was the "diagonal-dot-pitch" that you were calculating.
Although,it is quite self-explanatory.
It might help to clearify the matter at hand for those who haven't had their coffee yet...he he...


Dear Anonymous...

" FAIL! "

You are both right.
As "Brent V" pointed out.
Dot-Pitch equals the distance between the same point on two dots of the same colour f.ex. green-to-green,etc,etc...
Depending on which method was used to make the display.
F.ex. in a display with triangular-pixels the "dot pitch" is the width of the pixel,or triad as it is also called...,since one triad or pixel consists of one Red,one Green,and one Blue dot.
That includes the distance between the dots.

Thank you for taking the time to read this.

Leslie Lim said...

Wow. Awesome article. Please do more articles like this in the future. Very informational and knowledgeable. I will expect more from you in the future. For now i will just bookmark your page and surely I'm gonna come back later to read more. Thank you to the writer!


Silvia Jacinto said...

Thanks for sharing such a wonderful article, I hope you could inspire more people. Visit my site too.

sarah lee said...

I really enjoyed reading your article. I found this as an informative and interesting post, so i think it is very useful and knowledgeable. I would like to thank you for the effort you have made in writing this article.

Moshe Rabinovich said...

Youre so cool! I dont suppose Ive learn anything like this before. So good to seek out anyone with some unique ideas on this subject. realy thanks for beginning this up. this website is something that's needed on the internet, somebody with a bit originality. helpful job for bringing one thing new to the web! online casino slots

John Benzema said...

I really appreciate you for such a great and informative article that you post through this blog. Normally what I do is figure out how many inches I want my image to be and then I multiply that by 72 (standard resolutions for the web for example are 72 dpi). So if I want an image on my site to be 4 in x 6 in, my image would be 4 x 72 = 288 by 6 x 72 = 432. 4 in x 6 in = 288 dpi x 432 dpi. Some programs let you choose the size in inches and ALSO let you choose the dpi so that you get a higher resolution per square inch.To calculate dpi of screen or screen density also the pixel per inch you can use this PPI Calculator,it shows the instant results.

Blogger said...

Easily Increase Your ClickBank Banner Traffic And Commissions

Bannerizer made it easy for you to promote ClickBank products by banners, simply visit Bannerizer, and get the banner codes for your favorite ClickBank products or use the Universal ClickBank Banner Rotator Tool to promote all of the available ClickBank products.

Sami Malik said...

it is very informative

Anonymous said...

Click here for free hot singles in your area!