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My laptop is HP 250 G2 with 15.6” diagonal LED-backlit HD2 anti-glare (1366 x 768). Please How do I know the dpi value?

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    For you It would be 100 ppi/dpi. Calculated using this website.
    – TheKB
    Commented Jun 15, 2016 at 18:41

4 Answers 4

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1366 x 768 pixels is 1567 pixels diagonally (Pythagorean theorem, √(13662+7682)=1567; and you thought you would never use that).

If the screen measures 15.6" diagonally, 1567 pixels / 15.6" is approximately 100 pixels per inch.

You won't get an exact PPI number unless the manufacturer publishes it or you measure the screen. The advertised diagonal measurement is often a nominal number and may include a little of the display panel behind the bezel.

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  • 4
    Never thought pythagorean theorem has something to do with displays!
    – Mohammed Shareef C
    Commented Jun 13, 2017 at 6:58
  • 6
    Pythagorean theorem has everything to do with Euclidean spaces, such as monitor surface
    – amuliar
    Commented Dec 29, 2017 at 17:32
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Assuming you are using Windows 7:

  • Go to Control Panel > Appearance and Personalization > Display
  • In the left(blue) column, click Set custom text size(DPI)

A window titled Custom DPI Scaling will pop up. It will show what percent of the "normal size"(default monitor DPI) it is scaled to and will allow you to adjust it.

You should see a ruler in the middle. Below that it will say 9 point Segoe UI at X pixels per inch.

The X is your current DPI.

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  • Which version of windows? Mine says "9 point Segoe UI" rather than at X pixels per inch.
    – Journeyman Geek ♦
    Commented Jun 5, 2016 at 23:31
  • Windows 7. The exact message it says on my computer is "9 point Segoe UI at 144 pixels per inch"
    – Anonymous
    Commented Jun 8, 2016 at 23:09
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    Might be worth mentioning the version then. Its not there in windows 10.
    – Journeyman Geek ♦
    Commented Jun 8, 2016 at 23:20
  • OK. Updated my answer.
    – Anonymous
    Commented Jun 9, 2016 at 0:59
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Try yourself: DPI Calculator

Formula:

PPI = √(pixels_horizontal^2 + pixels_vertical^2) / inches_diagonal

PPI = √(13662 + 7682) / 15.6 = 100.45

Therefore, 100.45 dpi

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as of DPI Calculator

  • Display size: 13.6" × 7.65" = 103.96in² (34.54cm × 19.42cm = 670.72cm²)
  • DPI = PPI = 100.45
  • 0.2529mm dot pitch, 10091 PPI²
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