PPI Calculator

Type a screen’s resolution and its diagonal to get its pixel density. Nothing is uploaded — there is no file here at all.

Pixel density

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Everything that follows from the resolution and diagonal above

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DPI Converter Retag or resample print DPI Pixels to Inches Convert px to inches, cm or mm at any DPI Print Readiness Check DPI & print size

This page cannot read your screen

A browser knows how many CSS pixels a page has and a device pixel ratio, and neither says how big the glass is. So nothing here is filled in from your device. Take the resolution from the display settings and the diagonal from the spec sheet, and type both.

Working out a print size?

A picture has no diagonal of its own — its density is whatever you print it at. For that, Pixels to Inches turns a pixel count into a size at the DPI you choose. Nothing is uploaded on either page.

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How it works

The sum is the diagonal in pixels over the diagonal in inches

The width and height in pixels make a right triangle, so the diagonal in pixels is the square root of width squared plus height squared. Divide that by the diagonal in inches and you have pixels per inch. A 1920 by 1080 screen has a diagonal of 2202.9 pixels; on a 24 inch monitor that is 91.79 PPI, and on a 15.6 inch laptop the same pixels come out at 141.21.

Every answer names the diagonal it came from

A 27 typed as centimetres instead of inches gives a figure 2.54 times too high, and it looks just as believable. So the result line always repeats the resolution and the diagonal it used, with the inch value when you typed centimetres. If the number looks wrong, the line under it shows what went in.

Width, height and dot pitch assume square pixels

Dividing the horizontal pixel count by the PPI gives the panel width only if a pixel is as tall as it is wide, which is true of almost every screen sold today. The page says so under the table rather than hiding it. Dot pitch is the same figure turned around: 25.4 millimetres divided by the PPI, the distance from one pixel centre to the next.

A distance, not a sharpness grade

Labels like retina or sharp on a PPI number depend on how far away you sit, and nobody typed that. Instead the page gives the distance at which one pixel spans one arcminute, the usual figure for 20/20 vision. A 24 inch 1080p monitor reaches it at about 95 cm, a 27 inch 4K one at about 54 cm. Sit further back and single pixels blend; sit closer and they can be seen.

Frequently Asked Questions

How do I calculate PPI?

Square the horizontal pixel count, square the vertical one, add them and take the square root: that is the diagonal in pixels. Divide it by the diagonal of the screen in inches. For 2560 by 1440 on a 27 inch monitor the diagonal is 2937.2 pixels, which gives 108.79 PPI.

What is the PPI of a 1920x1080 screen?

It has none until you know the size. The same 1920 by 1080 is 91.79 PPI on a 24 inch monitor, 81.59 on a 27 inch one and 141.21 on a 15.6 inch laptop. Resolution counts the pixels; the diagonal decides how tightly they are packed.

Can this page find my own screen's PPI?

No, and a page that says it can has guessed. A browser exposes CSS pixels and a device pixel ratio, and neither carries the physical size of the glass. Read the resolution from your display settings and the diagonal from the spec sheet or the box, and type both in.

My diagonal is in centimetres. Does that work?

Yes. Pick Centimetres as the unit and the page divides by 2.54 before doing anything else, then shows the inch value it used. A 61 cm 1080p screen comes out at 91.73 PPI. Typing a centimetre figure with Inches selected is the most common way to get a wildly high answer.

Is the advertised diagonal exact?

Often not quite. Screen sizes are marketed as round numbers, and the visible area can be a little smaller than the headline figure, especially on televisions and older monitors. If you can measure the lit area corner to corner, that measurement gives a truer PPI than the number on the box.

What is dot pitch?

The distance from the centre of one pixel to the centre of the next, usually given in millimetres. It is 25.4 divided by the PPI, so a 91.79 PPI monitor has a dot pitch of about 0.277 mm and a 163.18 PPI one about 0.156 mm. Smaller means the pixels are closer together.

How much PPI is enough?

It depends on how far away you sit, which is why this page gives no grade. It gives the distance at which one pixel spans one arcminute, the usual figure for 20/20 vision: further than that and single pixels blend together. A 55 inch 4K television reaches it at about 109 cm, a 27 inch 4K monitor at about 54 cm.

Is PPI the same as DPI?

They are often used as one word. Strictly, PPI counts pixels on a screen or in an image, and DPI counts the ink dots a printer lays down. For a screen there are no ink dots, so PPI is the right term. For working out how big a picture prints, the DPI you choose is what matters, and our Pixels to Inches page does that sum.

Why is the width shown different from my monitor's outside width?

The width and height here are the panel the pixels fill, not the case around it. The bezel and stand add to the outside measurement. They also assume square pixels, which is true of almost every modern screen; on the rare display that is not, the width and height would be off while the PPI along the diagonal would not.

Is anything uploaded or stored?

Nothing. There is no file, no server call and no account. The sum runs in JavaScript on your own device, and the numbers you type are not sent anywhere or kept once you close the tab.

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