DPI vs PPI: Image Resolution for Print and Screen, Explained (2026)

DPI vs PPI: Image Resolution for Print and Screen, Explained (2026)

Every week, a designer sends a printer a file that says 300 DPI and gets back a soft, disappointing print, or exports a web banner at 72 DPI because a tutorial said screens are 72 DPI, and cannot work out why the number changed nothing. Both mistakes come from the same misunderstanding. The DPI or PPI value stored in an image file is a note about intended size, not a measure of quality. The quality is in the pixel count, and the pixel count is the only number that cannot lie to you.

This guide settles the three terms, gives you the one formula that connects pixels to print size, works the arithmetic on real print sizes, and then deals with screens, where the rules are different again. If you only remember one line, make it this: pixels divided by inches equals PPI, and everything else is commentary.

PPI, DPI and the Resolution Tag

• PPI (pixels per inch) describes your image. It is the number of pixels from the file that land in one inch of output. PPI is not stored magic; it is computed: pixel width divided by print width in inches.
• DPI (dots per inch) describes a printer. It counts the dots of ink or toner the device places in one inch. A printer needs several dots to reproduce one pixel's colour, which is why printer DPI figures (1,440, 2,880) dwarf image PPI figures without meaning your file should match them. Epson's support knowledge base states the split in one line each: PPI relates to what a monitor shows, DPI to what a printer prints.
• The file's resolution tag is metadata. Writing "300" into the PPI field of a 800 by 600 image does not add a single pixel. It only tells layout software "place this at 2.67 inches wide by default". The same image tagged 72 PPI places at 11.1 inches wide by default, with exactly the same pixels spread thinner.

The working formula, the same one graphics documentation has used for decades (NVIDIA's X driver documentation writes it as DPI equals size in pixels divided by size in inches):

PPI = pixel dimension ÷ output size in inches, and its partner, pixels needed = output inches × target PPI.

Everything in print resolution is those two divisions. The rest of this guide is applying them honestly.

The Three Numbers, Properly Separated

Pixels are the asset. A 4000 by 3000 image contains 12 million pixels of information. That count is fixed at capture or creation. No setting in any export dialog increases it; resampling can interpolate more pixels, but interpolation invents averages, not detail.

PPI is a ratio, not a property. The same 4000 by 3000 file is 300 PPI when printed 13.3 inches wide, 150 PPI when printed 26.7 inches wide, and 100 PPI across a 40 inch banner. Nothing about the file changed; only the size you spread it over changed. This is why asking "what PPI is this image?" without a print size has no answer.

DPI belongs to hardware. Dots are physical marks. Because a printer has only a handful of ink colours, it lays down clusters of dots to fake each pixel's exact shade, so device DPI runs into the thousands while the image feeding it sits at a few hundred PPI. When a print shop says "send 300 DPI files", they mean 300 PPI images. The shorthand is universal and harmless as long as you know which number you control.

A fourth term appears only in commercial offset printing: LPI (lines per inch), the row count of the halftone screen a press uses. Adobe's print production material gives the working relationship: aim for a PPI of roughly twice the LPI. A magazine printed at 150 LPI wants about 300 PPI from you, a newspaper at 85 LPI wants about 170. If nobody has mentioned LPI, you are not on an offset press job and can ignore it.

Worked Table: Pixels Needed for Common Print Sizes

Pixels needed = inches × target PPI. The targets are the conventions print services publish: 300 PPI for work viewed at reading distance, 200 for larger pieces, 150 for posters and banners viewed a few feet away. Every figure below is that multiplication, nothing more exotic.

Read the table in the direction you actually work. Designing a poster? Start from the row, pick the column that matches how close viewers stand, and you have the pixel dimensions to build the file at. Checking a photo you already have? Divide its pixels by the print width and see which column it lands in.

Worked example, start to finish. A camera file is 6000 by 4000 pixels (24 megapixels). How large can it print at the 300 PPI photo standard? 6000 ÷ 300 = 20 inches wide; 4000 ÷ 300 = 13.3 inches tall. At 240 PPI, a level many labs accept for larger prints, it reaches 25 by 16.7 inches. At 150 PPI it covers 40 by 26.7 inches, poster territory, where viewers stand back. One file, three honest answers, all from the same division.

The reverse check. A client supplies a logo rasterised at 1000 by 1000 and wants it 8 inches wide on a brochure. 1000 ÷ 8 = 125 PPI. That is below any print convention for close viewing, and no export setting fixes it. The answers are a smaller placement (at 3.3 inches wide it is a true 300 PPI), the vector original, or a rebuild. The image formats guide covers when a raster should never have been the deliverable in the first place.

Effective PPI: The Number That Actually Prints

Layout software adds one more wrinkle, and print professionals have a name for it: effective resolution, the PPI after scaling in the layout is taken into account (the term and definition are Adobe's, from its print production documentation). Place a 2400 pixel wide image at 8 inches and it is effectively 300 PPI. Scale it up to 12 inches in the layout and it is effectively 200 PPI, whatever the file's tag claims, because the same pixels now cover more paper. Scale it down to 6 inches and it is effectively 400 PPI, which is wasted data but never a quality problem.

This is the check to run before anything goes to print: not "what does the file say", but "what does each placed image divide out to at its placed size". Every prepress problem in this area is an effective PPI problem that a file tag hid. The export step can change the answer again: PDF presets resample placed images above a threshold (Affinity's professional presets, for example, downsample anything above 375 DPI to 300), so check those settings in the PDF/X-1a vs PDF/X-4 export guide before you send the file.

Which PPI Target Is Right?

The 300 figure is a convention, not a law of physics, and it comes from viewing distance. At reading distance, a healthy eye resolves detail at about the density 300 PPI provides, so extra pixels buy nothing. As the piece gets bigger, viewers stand further away, the same eye resolves less density, and lower PPI produces the same perceived sharpness. That geometry is why the conventions step down with size:

• 300 PPI: books, magazines, brochures, photos, anything held in the hand. The default when in doubt for print.
• 200 to 240 PPI: large photo prints, canvas, work viewed at arm's length or beyond. Most labs accept this range for big pieces because the viewing distance does the rest.
• 100 to 150 PPI: posters, banners, exhibition graphics, billboards at the far end. A 24 by 36 poster at 150 PPI (3600 by 5400 pixels, from the table) is a standard, accepted deliverable.
• Below 100 PPI: only for genuinely distant work, and only with the printer's agreement.

Two honest caveats. First, these are conventions that printers publish and accept work against, not guarantees; a print shop's own specification always wins over a guide, including this one. Second, sending more than the target is not wrong, just heavier: a 600 PPI file prints no sharper than the same image at 300, it only transfers slower.

Scanning: The Same Formula, Run Backwards

Scanners confuse the vocabulary one more time. A scanner's DPI figure is really samples per inch: how many pixels it captures from each inch of the original. Vendors often shorten that to DPI on the box, and scanners offer two figures, a true optical resolution and a higher interpolated one that invents pixels in software. Buy and scan on the optical figure; interpolation adds no detail, for the same reason upscaling a file does not.

The scan setting follows from the formula, run backwards. Decide the largest print you will ever make from the scan, pick its target PPI, and multiply by the enlargement:

Scan PPI = target print PPI × (print width ÷ original width)

Worked example. A 4 by 6 inch photo, and the biggest planned print is 8 by 12, twice the size in each dimension. At the 300 PPI print target: 300 × 2 = 600. Scan at 600 samples per inch, and the file comes out at 2400 by 3600 pixels (4 × 600 and 6 × 600), which prints at exactly 300 PPI at 8 by 12 (2400 ÷ 8 = 300). Archive scans for a family collection follow the same logic with the enlargement guessed generously: scanning once at a high setting is cheaper than finding the photo album again in ten years.

If the scan is only ever for screens, the enlargement is 1 and the calculation collapses to the original size: 300 samples per inch on a 4 by 6 photo gives 1200 by 1800 pixels, enough to fill a large monitor and to reprint at the same size later. Scanning documents for text follows the print rules at final size, with one addition: fine print and handwriting stay legible at 300, and 400 to 600 gives OCR software and future enlargements more to work with, at the cost of file size.

Screens Play by Different Rules

On screens, the PPI tag is ignored entirely. Browsers lay images out by pixel dimensions and CSS, and a file tagged 72, 300, or 10,000 PPI displays identically if the pixel dimensions match. The "72 DPI for web" rule is a leftover from early Macintosh displays and has described nothing real for decades. CSS defines its own fixed inch (96 CSS pixels per inch) for the rare cases where physical units appear in a stylesheet, and that is a layout constant, not a quality setting. The px, rem, and em guide covers that unit system.

What screens actually vary is device pixel density. A laptop with a high-density display may show a 1200 CSS pixel wide slot using 2400 device pixels. Serve a 1200 pixel image into that slot and it looks soft, not because of any tag, but because the display is asking for twice the pixels you sent. The fix is supplying larger pixel dimensions and letting srcset pick, which is the whole subject of the responsive images guide. For screen work, then, the only questions are: how many pixels does the slot need at 1x, 2x, and maybe 3x density, and how much weight can the page afford. Resolution tags answer neither.

Vector graphics leave this entire discussion. An SVG has no pixel grid, so it has no PPI at any size, which is one reason icons and logos belong in vector form. Preparing those files is covered in the SVG optimisation guide.

The Five Mistakes That Cause Soft Prints

1. Changing the tag instead of the pixels. Setting 300 in the resolution field with resampling off changes only the default print size. The print comes back exactly as soft, with paperwork that claims otherwise.

2. Upscaling and expecting detail. Resampling a 1000 pixel image up to 3000 pixels gives you 3000 pixels of smooth interpolation. It can help a large print look less jagged, and dedicated upscalers guess detail better than plain interpolation, but neither recovers information that was never captured. Start from a bigger source whenever one exists.

3. Judging sharpness at 100% zoom on screen. At 100%, your monitor shows the image at its own density, typically making effective PPI look worse than print will. Judge by the division (pixels ÷ inches), or print a small test crop at final size.

4. Exporting print files from a screen-sized canvas. A design built at 1200 pixels wide for a web banner cannot become an 8 inch print at 300 PPI, because 8 inches at 300 needs 2400. Build print work at print pixel dimensions from the start; the table above is the shopping list.

5. Sending a printer your biggest file "to be safe". A 200 MB file at 900 effective PPI slows the job, may get downsampled by the printer's pipeline without telling you, and gains nothing. Send the target PPI for the size, plus bleed and crop marks if the printer asks for them.

Pre-Print Checklist

1. List every raster image in the piece and its placed size in inches or centimetres (25.4 mm to the inch; pixels ÷ PPI gives inches, multiply by 25.4 for millimetres).
2. Divide each image's pixel width by its placed width. That is the effective PPI that will actually print.
3. Compare against the target for the viewing distance: 300 close, 200 to 240 middle, 100 to 150 far.
4. Fix any shortfall by shrinking the placement, sourcing a larger file, or switching the element to vector, in that order of preference.
5. Export with resampling set deliberately: downsample excess, never upsample silently, and confirm the export's pixel dimensions, not its tag, match the plan.
6. Send the printer the file and the finished dimensions, and let their specification override any convention in this guide.

Resolution is only one of three checks a print file has to pass. The other two are color and trim: the CMYK vs RGB print color guide explains why bright screen colors dull on paper and how to convert with the printer's profile, and the bleed, trim and safe area guide works out document sizes with bleed for common products.

Frequently Asked Questions

Is DPI the same as PPI?

Not technically, and the difference matters when you talk to hardware. PPI counts the pixels in your image per inch of output; DPI counts the dots a printer places per inch of paper. A printer uses many dots to reproduce one pixel, so its DPI figure is far higher and is not a target for your file. In everyday designer shorthand, "300 DPI image" means a 300 PPI image, and everyone in print production understands it that way. Just remember which of the two numbers you control: the pixels.

What resolution do I need for a poster?

Work backwards from size and viewing distance. A 24 by 36 inch poster is normally viewed a few feet away, and the standard deliverable is 150 PPI, which is 3600 by 5400 pixels. If the poster will also be read up close (an exhibition panel with body text, say), use 200 PPI, 4800 by 7200 pixels. Only hand-held work truly needs 300.

Does DPI affect file size or web loading?

No. File size follows pixel dimensions and compression, never the resolution tag. A 1200 by 800 image tagged 72 PPI and the same image tagged 300 PPI are byte for byte the same weight and load identically, because browsers ignore the tag. If a web image is heavy, it has too many pixels for its slot or too little compression, and the image formats guide is the place to fix that.

How do I check an image's real print resolution?

Divide. Take the pixel width and the intended print width in inches: 3000 pixels at 10 inches is 300 PPI. Image editors show this as the document size and resolution fields, but the resolution field is only restating that division against the stored default size. At the size you actually place it, your division is the truth.

Can I turn a 72 PPI image into a 300 PPI image?

You can change the tag in seconds, which changes nothing but the default print size: the image simply places smaller. You can also resample up, which manufactures pixels by interpolation and adds no real detail. What you cannot do is recover detail the original never had. If the piece matters, get a larger original; if none exists, place the image smaller, where its honest PPI is higher.

Why does my print look soft when the file says 300 DPI?

Because the tag is not the print. The usual causes, in order: the image was placed larger than its pixels support, so its effective PPI was far below 300; the export downsampled the pixel dimensions while leaving the tag alone; or the softness was in the source (focus, motion, aggressive JPEG compression) and no resolution setting could have saved it. Check effective PPI first: pixels divided by placed inches. It answers most cases in one calculation.

Sources Read for This Guide

• Epson support knowledge base, article KB020020, "What is the difference between PPI and DPI?": PPI as the monitor and pixel measure, DPI as the print and dot measure.
• Adobe print production material and InDesign documentation discussions: the definitions of PPI, effective resolution after scaling, and DPI as a device property, and the offset printing rule that target PPI runs at about twice the press LPI (65 LPI newspaper to 130, 150 LPI magazine to 300, 175 LPI art publication to 350).
• NVIDIA X driver documentation, "Dots Per Inch" appendix: the formula DPI equals size in pixels divided by size in inches, with the millimetre conversion at 25.4 mm per inch.

Conventions such as 300 PPI for hand-held print are the published house standards of print services and labs rather than figures from a single document; where a printer gives you its own specification, that specification wins. All arithmetic in this guide is the pixels ÷ inches formula applied to the stated sizes, and can be checked with a pocket calculator.