DPI vs PPI: What Resolution Do You Need for Print and Screen?

PPI (pixels per inch) is how many of your image’s pixels land on each inch of a print or screen. DPI (dots per inch) is how many ink dots a printer lays down per inch. For a print viewed in the hand you need about 300 PPI, so divide the pixel dimensions by 300 to get the size in inches. Larger prints seen from farther away need less: around 150 to 200 PPI at arm’s length and 100 or below across a room.

This is the full reference for the question “what DPI or PPI do I need?”. The print size calculator does the arithmetic for one file, and preparing photos for print covers colour, paper and proofing. This page explains the ideas underneath both: what each number measures, why the value stored in a file does nothing on a screen, how viewing distance sets the PPI you need, the difference between resizing and resampling, and what to send a lab.

PPI and DPI measure two different things

A digital photograph is a grid of pixels, for example 6,000 across and 4,000 down. That grid has no physical size. It gains one only when it is output, and PPI describes that output: the number of image pixels spread along one inch of paper or screen. Print the 6,000 pixel side across 20 inches and the print is 300 PPI. Print the same file 40 inches wide and it is 150 PPI. The file has not changed. Only the spacing has.

DPI belongs to the printer. An inkjet printer cannot vary the darkness of a single droplet much, so it builds each tone and colour from a cluster of tiny dots of a few ink colours, scattered in a fine pattern. It needs many dots to reproduce one image pixel, which is why printer figures such as 1,440 or 2,880 DPI are so much higher than the 300 PPI of the file. A higher DPI setting gives smoother tone and finer dot patterns. It does not add detail that the file lacks.

In everyday speech the two terms are mixed up constantly. When a lab, a publisher or a competition asks for “a 300 DPI file”, they mean 300 pixels per inch at the printed size. Scanner settings are also labelled DPI, although what they count is samples, which become pixels.

Where “300” comes from

Press printing breaks a picture into a regular grid of halftone dots, measured in lines per inch. The long-standing rule in publishing is to supply about twice as many pixels per inch as the line screen, and twice a 150 line screen is 300. The figure also suits the eye: at a normal reading distance of roughly 12 inches (30 cm), someone with good vision cannot separate details much finer than that. Photo lab machines that expose light-sensitive paper commonly work at about 300 PPI, and many photo inkjet printers work internally at 300 or 360 PPI depending on the make. So 300 is a sound target for close viewing, not a law.

Why the DPI number stored in a file changes nothing on screen

Image files carry a small piece of metadata called resolution, shown in editing software as something like “72 pixels/inch” or “300 pixels/inch”. It is a note, not a property of the picture. It records how large the file should be printed if nobody says otherwise. Cameras write whatever value their maker chose, commonly 72, 240, 300 or 350, and it tells you nothing about image quality.

Take one 6,000 x 4,000 pixel photograph and save it twice, once tagged 72 and once tagged 300. The two files have the same pixels, the same detail and the same size on disk. On a screen they are indistinguishable, because screens, browsers, phones and social platforms place images by pixel dimensions and ignore the tag completely.

The tag matters in exactly three places:

• Page layout and word processing software reads it to decide how big a placed picture starts out. A 3,000 pixel wide image tagged 300 arrives 10 inches wide, and tagged 72 it arrives nearly 42 inches wide. You can drag it to any size afterwards.
• Printing straight from an editor at “actual size” uses the tag to set the paper dimensions.
• People who check it. Some publishers and competitions reject files whose tag is not 300, even when the pixel count is ample. Changing the tag without resampling (see below) satisfies them and alters nothing else.

Screen density and the 72 PPI myth

“Save for the web at 72 DPI” is advice left over from early desktop screens that showed about 72 pixels per inch. It was never an instruction that browsers obeyed, and screens have long since moved on. Every display has its own fixed density, which you can work out by dividing the diagonal in pixels by the diagonal in inches. A 27 inch monitor showing 2,560 x 1,440 pixels is about 109 PPI. The same size at 3,840 x 2,160 is about 163 PPI. Laptops range from roughly 130 to 250 PPI and phones from about 300 to more than 500, because they are held closer.

For screens, think in pixels only. High-density displays use two or three physical pixels for every layout pixel a web page specifies, so a picture shown in an 800 pixel wide column looks crisper if the file is 1,600 pixels wide. That is the whole of screen “resolution”: supply enough pixels for the largest size at which the image will be shown, and no more. Suitable long-edge sizes for websites, email and social platforms are listed in the guide to exporting photos.

How to work out print size from pixel dimensions

Three versions of one formula cover every case:

• Print size = pixels divided by PPI. For centimetres, multiply the result by 2.54.
• Pixels needed = print size in inches multiplied by PPI. From centimetres, divide by 2.54 first.
• PPI you will get = pixels divided by print size in inches.

Work each side separately. A 6,000 x 4,000 file printed 30 inches wide gives 6,000 divided by 30, which is 200 PPI. A 40 x 50 cm print at 300 PPI needs 40 divided by 2.54, times 300, which is about 4,724 pixels on the short side and 5,906 on the long side.

Check the shape as well as the count. If the file and the paper have different aspect ratios, part of the picture will be trimmed or a border added, and the pixels that remain after cropping are the ones that count. A 6,000 x 4,000 frame cropped to 8 x 10 proportions keeps only 5,000 x 4,000 pixels.

Notice how slowly print size grows with megapixels. Doubling the pixel count widens the print by only about 41 percent at the same PPI, because the extra pixels are shared between width and height. A fuller list of camera resolutions is in the megapixel table.

The PPI you need depends on viewing distance

The eye resolves angles, not inches. A person with normal vision can separate details about one sixtieth of a degree apart. Up close that angle covers a tiny patch of paper, and from across a room it covers a large one. So the pixel density beyond which a print cannot look any sharper falls in direct proportion to distance:

• PPI at the limit of normal vision = 3,438 divided by the viewing distance in inches
• or 8,732 divided by the viewing distance in centimetres

That limit is a floor for “looks continuous”, not a guarantee. Sharp-eyed viewers, and high-contrast edges such as text, fine branches or wires against sky, reveal a little more. The practical targets below add a margin for that.

Two cautions. First, decide the distance honestly. A large landscape in a gallery or a living room invites people to walk right up to it, and a print that holds 150 PPI or more rewards them. A canvas above a staircase will never be seen from closer than a few feet. Second, PPI is not the only limit on sharpness. Missed focus, camera shake and heavy noise reduction all remove detail before the pixel count comes into it, and a soft file at 300 PPI looks worse than a crisp one at 180. Sizes and distances for pictures at home are covered in how to hang photos.

Resizing versus resampling

Image size dialogs in editing software have a checkbox usually labelled “Resample”. It is the most important control in the dialog, and it separates two operations that are often confused.

Resizing without resampling (box unticked) changes only the resolution tag and therefore the stated print size. Width, height and resolution are locked together: raise the PPI and the inches shrink, lower it and they grow. The pixel dimensions stay fixed, and the picture is not altered in any way. Use this to see what PPI a file gives at a certain print size, or to set the tag to 300 for someone who insists on it.

Resampling (box ticked) changes the number of pixels. The software calculates a different grid from the old one.

• Downsampling throws pixels away. Do it for screens, where a 6,000 pixel file is far more than a web page can show. Detail that is removed cannot be put back, so keep the full-size original and downsample a copy.
• Upsampling (interpolation) creates pixels in between the existing ones. Conventional methods such as bicubic estimate each added pixel from its neighbours, which smooths the stair-stepping you would otherwise see on edges but adds no real detail. Machine-learning upscalers go further and generate plausible texture. They can look convincing on foliage, fabric and rock, and wrong on faces, lettering and regular patterns, so inspect the result at 100 percent.

When upsampling is worth doing

If the file gives roughly 180 PPI or more at the print size, leave it alone: the printer’s own software scales it smoothly. Below about 150 PPI for a print that will be seen up close, a careful upsample to the printer’s working resolution usually looks better than letting visible pixel edges through. Aim for no more than about double the original dimensions with conventional methods. Apply output sharpening after resampling, never before, because resampling softens edges and enlarges any sharpening halos already in the file.

Scanning is the one place PPI is set at capture

A scanner’s setting is real sampling density. Pixels produced = inches of original multiplied by scan PPI. A 6 x 4 inch print scanned at 600 PPI becomes 3,600 x 2,400 pixels. A 35mm frame, about 1.42 x 0.94 inches, scanned at 4,000 PPI becomes roughly 5,670 x 3,780 pixels. Decide the largest print you want, work out the pixels it needs, and scan to suit. See digitizing old photos and scanning film negatives for settings.

What to send a print lab

1. Find the lab’s file requirements. Most state a preferred PPI (commonly 300, sometimes 240 or 254), a colour space and accepted file types. Those instructions override any general rule, including this page.
2. Crop to the proportions of the print size so the lab’s software does not choose the crop for you.
3. Check the PPI you will get. Divide the pixel dimensions by the print size in inches. If the result is at or above the lab’s figure, send the file as it is or downsample to exactly the requested size. Sending more pixels than requested does no harm beyond a slower upload.
4. If you are short of pixels, compare the PPI with the viewing-distance table. Often it is already enough. If not, either choose a smaller print or upsample carefully and inspect the result.
5. Do not upsample just to make the tag say 300. Set the tag without resampling. An ordering page that warns about “low resolution” is applying a simple threshold and knows nothing about viewing distance.
6. Convert to the colour space the lab asks for. For most consumer labs that is sRGB. The reasons are in color space explained.
7. Save in the format requested: usually a maximum-quality JPEG, or a TIFF for fine-art work. The trade-off is discussed in JPEG or TIFF for prints.
8. Allow for trimming. Borderless prints and canvas wraps lose a small strip at each edge, so keep signatures and important detail away from the border.

If you print yourself, the same arithmetic applies, and the driver settings are covered in how to print photos at home.

Common mistakes

• Changing 72 to 300 and expecting a sharper picture. The tag does not touch the pixels. Fix: look at the pixel dimensions and divide by the print size.
• Typing 300 with Resample ticked. The software quietly multiplies the pixel count and the file balloons with invented data. Fix: untick Resample when you only want to change the tag or check a print size.
• Quoting DPI without a size. “300 DPI” on its own describes nothing: a 300 pixel wide thumbnail is “300 DPI” at one inch wide. Fix: always state pixel dimensions, or PPI together with print size.
• Refusing to print large because the file is “only” 150 PPI. Fix: check the viewing distance. At arm’s length and beyond, 150 PPI is often indistinguishable from 300.
• Downsampling the original. Saving a web-sized version over the master file discards detail for good. Fix: export copies and keep the full-resolution file.
• Confusing the printer’s DPI setting with file PPI. Choosing 2,880 DPI in the driver does not require a 2,880 PPI file. Fix: prepare the file at 240 to 360 PPI and let the driver place the dots.
• Counting pixels before cropping. Fix: crop to the print proportions first, then check the PPI.

Try this

Open one of your photographs in an editor and find the image size dialog. Untick Resample. Type 300 into the resolution field and note the width and height in inches or centimetres: that is the largest print for close viewing. Now type 150 and note the size again: that is a comfortable wall print. Confirm that the pixel dimensions did not move. Next, tick Resample, set the width to 2,000 pixels, and watch the pixel count and the estimated file size drop: that is a web copy. Cancel without saving. Finally, work out the density of the screen you are using from its pixel dimensions and diagonal. In fifteen minutes you will have handled every number on this page with your own file.

Frequently asked questions

What DPI do I need for printing photos?

Supply about 300 pixels per inch at the print size for anything held in the hand, and 150 to 200 for framed prints seen from arm’s length or farther. Multiply the print dimensions in inches by that figure to find the pixels you need.

Is 72 DPI or 300 DPI better for the web?

Neither: it makes no difference. Screens show images by pixel dimensions and ignore the stored value. Choose the right number of pixels on the long edge instead.

How do I make a photo 300 DPI?

Open the image size dialog, untick Resample and type 300 in the resolution field. The print size shown is what the file supports at that density. If you need a larger print at 300, the file needs more pixels, which means upsampling or a higher-resolution original.

Does a higher DPI mean a larger file?

Not by itself. File size follows the number of pixels and the compression used. Two files with the same pixel dimensions are the same size whatever the tag says. A scan made at a higher setting is larger because it really does contain more pixels.

How large can I print a 12 megapixel photo?

About 13 x 10 inches (34 x 25 cm) at 300 PPI, 20 x 15 inches (51 x 38 cm) at 200 PPI, and around 27 x 20 inches (68 x 51 cm) at 150 PPI for viewing from a few feet, provided the picture is sharp to begin with.

Related guides

• Print size calculator: enter your pixel dimensions and a print size to see the PPI.
• Preparing photos for print: colour spaces, soft proofing and paper choice.
• Exporting photos: pixel sizes, formats and sharpening for each destination.
• Megapixel table: pixel dimensions for common sensor resolutions.
• Sharpening: output sharpening after resizing.
• Displaying large photo prints: substrates, mounting and lighting for big pieces.
• How to print photos at home: printer settings, paper and profiles.
• Color space explained: which colour space to send and why.