How do you calculate PPI?

Measure the screen in pixels across its diagonal, then divide by the diagonal in inches. For 1920 x 1080 the pixel diagonal is the square root of 1920 squared plus 1080 squared, which is 2202.907 pixels; on a 24 in panel that is 2202.907 divided by 24, or 91.79 PPI. The same panel at 27 in is 81.59 PPI, because the pixels are spread over more glass. Pixel pitch is the same answer turned around: 25.4 mm divided by 91.79 gives 0.2767 mm between the centres of neighbouring pixels.

Is PPI the same as DPI?

Not on a screen. PPI here is the number of physical display pixels per inch. An image's resolution metadata sets a suggested print size, while printer DPI counts ink dots. Changing a photo's resolution metadata without resampling leaves its pixel dimensions unchanged; a viewer can still apply its own zoom or scaling. This page calculates screen density and does not inspect image files or convert printer DPI to PPI.

What is the PPI of common monitor sizes?

At 16:9 the usual ones come out like this: 1920 x 1080 at 24 in is 91.79 PPI, the same resolution at 27 in is 81.59; 2560 x 1440 at 27 in is 108.79; 3840 x 2160 at 27 in is 163.18 and at 32 in is 137.68. Laptops sit higher, since the same pixels are packed into a smaller diagonal: 2560 x 1600 at 13.3 in is 226.98 PPI. Type any of these into the fields to see the pitch and the panel size that go with them.

Why does my answer differ from the PPI the manufacturer quotes?

A rounded diagonal can change the answer. A 1920 x 1080 rectangle at 23.8 in is 92.56 PPI rather than the 91.79 PPI calculated at 24 in. Similarly, 2532 x 1170 at 6.1 in reads 457.25 PPI. Use the diagonal and native resolution from the same screen specification. Different measurement conventions, cutouts or subpixel layouts can also limit comparisons.

What is pixel pitch, and why would I want it?

Pixel pitch is the distance from the centre of one pixel to the centre of the next, and it is what LED wall and industrial display specifications quote instead of PPI. It is 25.4 divided by the PPI, in millimetres: 0.2767 mm at 91.79 PPI, 0.1557 mm at 163.18 PPI. A smaller pitch means the pixels sit closer together, which is why pitch is quoted for panels that are viewed from a fixed distance.

Does a higher PPI always mean a sharper picture?

Not on its own. Sharpness as the eye sees it depends on viewing distance as well as density, which is why a phone at 457.25 PPI and a desk monitor at 91.79 PPI can both look clean. Subpixel layout matters too, and this page does not model it: an RGB stripe panel, a PenTile panel and a WOLED panel at the same PPI do not resolve fine text equally. The number here is geometry, not a verdict on a screen.

Can it handle centimetres, ultrawide panels and odd resolutions?

Yes. The unit buttons take the diagonal in inches, centimetres or millimetres, so 60.96 cm and 24 in give the same 91.79 PPI, and a unit typed into the field is accepted when it agrees with the buttons and refused with a message when it does not. Shapes are reduced exactly rather than rounded to a marketing ratio: 3440 x 1440 is reported as 43:18, and 1366 x 768 as 683:384. A diagonal of 0 is refused, because PPI is undefined there.

Can I calculate PPI for a 4K TV, laptop, phone or Retina display?

Yes, when you know its native pixel width, pixel height and physical diagonal. The same calculation applies to each rectangular screen. A resolution label or a display name such as Retina alone is not enough to determine PPI. Enter physical panel pixels rather than a browser's CSS dimensions or a scaled desktop resolution. The page does not detect your screen or judge whether individual pixels will be visible.

Can I convert screen PPI to printer DPI or LPI?

There is no universal conversion from a screen's PPI to a printer's DPI. Printer dots and image pixels measure different things, and LPI describes halftone screen frequency. This calculator has no printer or halftone conversion mode. It also does not read an image's effective print resolution or change its metadata.

Which inputs and precision does the calculator support?

Each pixel dimension must be a whole number from 1 to 1,000,000. The diagonal must be between 0.1 and 1,000 inches, or the equivalent in centimetres or millimetres. Use a period for decimals; commas and spaces are treated as grouping separators. Choosing a unit reinterprets the typed diagonal in that unit, so enter its matching value. PPI normally shows two decimals; very small positive results use scientific notation instead of appearing as zero. Panel dimensions and the notes are also rounded for display.

PPI Calculator

Pixels per inch is one division: the diagonal measured in pixels, which is the square root of the width squared plus the height squared, over the diagonal measured in inches. This page does that division and then keeps the numbers that follow from it apart instead of folding them into one figure, so a 1920 x 1080 panel sold as 24 in reads 91.79 PPI, a pixel pitch of 0.2767 mm and a panel 20.92 by 11.77 in. The working is printed under the fields, the unit buttons take a diagonal in inches, centimetres or millimetres, and anything that cannot be read is refused with a sentence saying why rather than shown as a zero.

Pixels per inch91.791920 x 1080 at 24 in · pixel diagonal 2202.907 · pitch 0.2767 mm

PPI: 91.79
Pixel pitch: 0.2767 mm
Panel width: 20.92 in
Panel height: 11.77 in

The screen

The resolution the panel runs at, and the diagonal it is sold as, measured corner to corner. A number that cannot be read gets a line above saying why, never a silent zero.

Pixel widthPixel heightScreen diagonalDiagonal measured in

sqrt(1920^2 + 1080^2) = 2202.907 px across the diagonal, divided by 24 in = 91.79 PPI
1920 x 1080 is 2,073,600 pixels, 2.07 megapixels, in the shape 16:9.
Square pixels, so the panel itself measures 20.92 in by 11.77 in.
Pixel pitch 0.2767 mm, or 276.7 micrometres, centre to centre between neighbouring pixels.
91.79 PPI is 36.14 pixels per centimetre.
This is the display's own pixel density. The DPI tag stored inside a JPEG or PNG is print metadata: editing it changes nothing on this panel.

Worked cases

Each one is run through the same function the fields above are, refusal included.

1920 x 1080 at 24 in16:9 panel
91.79 PPI
3840 x 2160 at 27 insame shape, 4K
163.18 PPI
Diagonal 0any resolution
refused, PPI is undefined

One flat rectangle of square pixels. For a curved panel, rounded corners or a notch, check whether the stated diagonal measures the full bounding rectangle; this model does not describe the curved surface or cutouts.
Makers round the diagonal. The same panel measured at 23.8 in reads 92.56 PPI instead of 91.79, so a spec sheet that says 24 in and means 23.8 in moves the answer.
Subpixels are not counted. An RGB stripe, a PenTile layout and a WOLED panel at the same PPI do not resolve the same detail.

Accuracy. PPI is the pixel diagonal, which is the square root of width squared plus height squared, divided by the physical diagonal you enter. Results are rounded for display. Panel width, height and pitch follow from it and assume square pixels in a plain rectangle. This is a display's own pixel density; it is not the DPI number stored in an image file, and the page says so.

Common questions

How do you calculate PPI?: Measure the screen in pixels across its diagonal, then divide by the diagonal in inches. For 1920 x 1080 the pixel diagonal is the square root of 1920 squared plus 1080 squared, which is 2202.907 pixels; on a 24 in panel that is 2202.907 divided by 24, or 91.79 PPI. The same panel at 27 in is 81.59 PPI, because the pixels are spread over more glass. Pixel pitch is the same answer turned around: 25.4 mm divided by 91.79 gives 0.2767 mm between the centres of neighbouring pixels.
Is PPI the same as DPI?: Not on a screen. PPI here is the number of physical display pixels per inch. An image's resolution metadata sets a suggested print size, while printer DPI counts ink dots. Changing a photo's resolution metadata without resampling leaves its pixel dimensions unchanged; a viewer can still apply its own zoom or scaling. This page calculates screen density and does not inspect image files or convert printer DPI to PPI.
What is the PPI of common monitor sizes?: At 16:9 the usual ones come out like this: 1920 x 1080 at 24 in is 91.79 PPI, the same resolution at 27 in is 81.59; 2560 x 1440 at 27 in is 108.79; 3840 x 2160 at 27 in is 163.18 and at 32 in is 137.68. Laptops sit higher, since the same pixels are packed into a smaller diagonal: 2560 x 1600 at 13.3 in is 226.98 PPI. Type any of these into the fields to see the pitch and the panel size that go with them.
Why does my answer differ from the PPI the manufacturer quotes?: A rounded diagonal can change the answer. A 1920 x 1080 rectangle at 23.8 in is 92.56 PPI rather than the 91.79 PPI calculated at 24 in. Similarly, 2532 x 1170 at 6.1 in reads 457.25 PPI. Use the diagonal and native resolution from the same screen specification. Different measurement conventions, cutouts or subpixel layouts can also limit comparisons.
What is pixel pitch, and why would I want it?: Pixel pitch is the distance from the centre of one pixel to the centre of the next, and it is what LED wall and industrial display specifications quote instead of PPI. It is 25.4 divided by the PPI, in millimetres: 0.2767 mm at 91.79 PPI, 0.1557 mm at 163.18 PPI. A smaller pitch means the pixels sit closer together, which is why pitch is quoted for panels that are viewed from a fixed distance.
Does a higher PPI always mean a sharper picture?: Not on its own. Sharpness as the eye sees it depends on viewing distance as well as density, which is why a phone at 457.25 PPI and a desk monitor at 91.79 PPI can both look clean. Subpixel layout matters too, and this page does not model it: an RGB stripe panel, a PenTile panel and a WOLED panel at the same PPI do not resolve fine text equally. The number here is geometry, not a verdict on a screen.
Can it handle centimetres, ultrawide panels and odd resolutions?: Yes. The unit buttons take the diagonal in inches, centimetres or millimetres, so 60.96 cm and 24 in give the same 91.79 PPI, and a unit typed into the field is accepted when it agrees with the buttons and refused with a message when it does not. Shapes are reduced exactly rather than rounded to a marketing ratio: 3440 x 1440 is reported as 43:18, and 1366 x 768 as 683:384. A diagonal of 0 is refused, because PPI is undefined there.
Can I calculate PPI for a 4K TV, laptop, phone or Retina display?: Yes, when you know its native pixel width, pixel height and physical diagonal. The same calculation applies to each rectangular screen. A resolution label or a display name such as Retina alone is not enough to determine PPI. Enter physical panel pixels rather than a browser's CSS dimensions or a scaled desktop resolution. The page does not detect your screen or judge whether individual pixels will be visible.
Can I convert screen PPI to printer DPI or LPI?: There is no universal conversion from a screen's PPI to a printer's DPI. Printer dots and image pixels measure different things, and LPI describes halftone screen frequency. This calculator has no printer or halftone conversion mode. It also does not read an image's effective print resolution or change its metadata.
Which inputs and precision does the calculator support?: Each pixel dimension must be a whole number from 1 to 1,000,000. The diagonal must be between 0.1 and 1,000 inches, or the equivalent in centimetres or millimetres. Use a period for decimals; commas and spaces are treated as grouping separators. Choosing a unit reinterprets the typed diagonal in that unit, so enter its matching value. PPI normally shows two decimals; very small positive results use scientific notation instead of appearing as zero. Panel dimensions and the notes are also rounded for display.

PPI is the pixel diagonal, which is the square root of width squared plus height squared, divided by the physical diagonal you enter. Results are rounded for display. Panel width, height and pitch follow from it and assume square pixels in a plain rectangle. This is a display's own pixel density; it is not the DPI number stored in an image file, and the page says so.