Is this the same as DPI?

For displays, DPI and PPI are often used interchangeably. Printers have separate DPI specs.

Can I use centimeters?

Enter diagonal inches (convert cm to inches) and use the pixels/cm output for metric workflows.

Why does my OS report a different PPI?

Some OS scaling modes use effective resolution, not native pixels. Use native resolution for true physical PPI.

Does scaling or zoom change PPI?

No. PPI is physical. Scaling just changes how many logical pixels map to the physical pixels.

How do I know if a screen is retina/hiDPI?

Higher PPI (typically 200+ for laptops/phones) is often marketed as retina/hiDPI, but it’s a marketing term—use PPI to compare sharpness directly.

tech calculator

Pixel Density Calculator

Find the PPI/DPI for any display by entering resolution and diagonal size.

Results

Pixels per inch (PPI): 108.79
Pixels per cm: 42.83
Screen width (in): 23.53
Screen height (in): 13.24

How to use this calculator

Enter resolution width/height in pixels.
Enter diagonal size in inches.
See PPI, pixels/cm, and the physical screen width/height.

Inputs explained

Resolution width/height: Native pixel dimensions of the display.
Diagonal size: Diagonal measurement of the viewable area in inches.

How it works

We compute the diagonal pixel count using the Pythagorean theorem, divide by the physical diagonal to get pixels per inch, then derive the physical width/height.

Pixels/cm uses the standard conversion of 1 inch = 2.54 cm.

Formula

Diagonal pixels = √(width² + height²)
PPI = diagonal pixels ÷ diagonal inches

When to use it

Comparing monitors or laptops for design and coding clarity.
Mapping responsive breakpoints to physical sizes for usability testing.
Checking if UI assets need higher density for retina/hiDPI screens.

Tips & cautions

Use native resolution for accurate PPI; scaled modes change effective density.
Bezel/rounded corners aren’t included—the math assumes the full diagonal is viewable.
PPI helps estimate how sharp text/icons will look; larger PPI means finer detail.
Assumes rectangular displays with stated diagonal; ultrawide aspect ratios are still supported but physical height/width depend on accurate diagonal.
Does not account for OS scaling factors; it’s physical PPI only.
HDR, brightness, and panel type are not considered—this is purely geometry.

Worked examples

27” 1440p monitor

Diagonal pixels ≈ 2932
PPI ≈ 108.8
Width ≈ 23.5 in
Height ≈ 13.2 in

13” 4K laptop

3840×2160 @ 13" ≈ 338 PPI

Deep dive

This pixel density calculator turns resolution and diagonal size into PPI, pixels/cm, and physical screen dimensions. Enter pixel dimensions and diagonal inches to compare monitor and phone sharpness.

Use it to plan responsive designs, choose retina assets, or compare displays for coding and creative work. It assumes the listed diagonal is fully viewable and uses native resolution for accurate PPI.

FAQs

Is this the same as DPI?: For displays, DPI and PPI are often used interchangeably. Printers have separate DPI specs.
Can I use centimeters?: Enter diagonal inches (convert cm to inches) and use the pixels/cm output for metric workflows.
Why does my OS report a different PPI?: Some OS scaling modes use effective resolution, not native pixels. Use native resolution for true physical PPI.
Does scaling or zoom change PPI?: No. PPI is physical. Scaling just changes how many logical pixels map to the physical pixels.
How do I know if a screen is retina/hiDPI?: Higher PPI (typically 200+ for laptops/phones) is often marketed as retina/hiDPI, but it’s a marketing term—use PPI to compare sharpness directly.

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Assumes the stated diagonal matches the viewable area. Bezel sizes or rounded corners can slightly alter physical dimensions.