Ask Different is a question and answer site for power users of Apple hardware and software. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I've recently purchased an Apple Thunderbolt 27" display and having connected my second monitor side by side, I can see the DPIs between the two displays are different.

My other monitor, a Samsung SyncMaster is 92dpi, so what DPI is the Thunderbolt display (and by inference) the Cinema Display?

Apple's site just lists the the dimensions and the panel size and you can estimate using basic math that the DPI is approximately 109.

However being the fact fascist that I am, 109dpi just sounds plain wrong; so either the assumption that the pixels are square is wrong, or the dpi is wrong (say 108 or 110) and the display is not quite 27"

Is there any empirical evidence of the display's DPI or pixel structure that will cement the DPI figures?

Is there an official statement from Apple (perhaps a slide in a Keynote somewhere) thats shows the actual DPI, or tech document I've missed that states it.

share|improve this question
In response to bmike's query above:- The iFixit teardown of the Apple Thunderbolt Display showed that the LG LM270WQ1 was being used. iFixit Apple TBD teardown – axeros May 7 '15 at 11:06

Your calculation is solid. Everywhere I've seen it 109 PPI (which is probably what you intend with DPI) is what people report for the Thunderbolt Cinema Display:

The TUAW article has this nice picture to catalog various pixels per inch densities:

TUAW illustration of PPI

The linked article above even has a Google-hosted spreadsheet with details on the data behind the table.

share|improve this answer
+1 for the answer, but it wasn't the definitive answer I was looking for. – Stu Wilson May 26 '12 at 20:37
up vote 4 down vote accepted

Ok, I've found the answer and it is confirmed at 109 PPI.

The panel in use in the display is an LG made panel with a part number of LM270WQ1 and the full tech specs of the panel (from 2009) are here.

The spec sheet denotes the pixel pitch at 0.2331mm (or 0.009177") which works out at 108.968 PPI

share|improve this answer
Awesome find. What ties the LG part number to Apple's part number? – bmike Mar 15 '14 at 16:49

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.