Is 300 DPI the same as 300 PPI?

No. 300 DPI describes a printer placing 300 ink dots per inch. 300 PPI means 300 image pixels per inch of printed page. Print shops often say DPI when they mean PPI, so when someone asks for a 300 DPI image, they want roughly 300 pixels per inch at the final size.

Does changing an image's DPI in Photoshop improve print quality?

No. Changing only the DPI field rewrites metadata; the pixel count stays the same. If you also resample to add pixels, you get interpolated detail rather than real detail. To raise effective PPI, either supply a larger original or print the image at a smaller size.

What PPI do I need for printing?

300 PPI suits offset printing and anything read up close. 200 to 300 PPI works for most digital press and photo books. Large-format prints viewed from a distance are often fine at 150 PPI. The right target depends on viewing distance as much as on the process.

How do I check the effective PPI of images in a PDF?

Open the PDF in PDF Preflight, which reads the resolution of each embedded picture at the size it is placed on the page and flags the ones below print target. It runs in your browser, so the file is never uploaded, and there is no file-size cap.

Why does my image show 72 DPI but print fine?

Because that 72 is metadata, not a measurement. If the file has enough pixels for the size it is placed at, it prints sharply regardless of the stored figure. Effective PPI, calculated from pixel dimensions and placed size, is the number that matters.

DPI vs PPI: What Printers Really Mean

Judge print sharpness by effective PPI at the placed size, not by the DPI tag stored in the file.

	DPI	PPI
What it measures	Ink dots a device can place	Image pixels per printed inch
Belongs to	Printers, presses, scanners	The image and its placed size
Decides sharpness	No — device spec only	Yes — this is the real test
Stored in file metadata	Often written, rarely meaningful	Not stored; must be calculated
Changes when resized	No	Yes — inversely with size
Used by print shops	Yes, as loose shorthand	Yes, as the actual target
Relevant for screen output	No	Only as a viewing guide

DPI describes how many ink dots a printer lays down per inch. PPI describes how many image pixels sit in each inch of a printed page. If you are preparing a file for print, use PPI as your working number and treat the DPI figure a printer quotes as a machine spec, not a property of your picture.

The exception is when you are choosing hardware or a print service. There, DPI is the right term, because it describes what the device can physically resolve.

When to use DPI

DPI belongs to output devices and to the language print shops use when they quote a job.

Printer and press specs. A 300 DPI laser printer, a 1440 DPI inkjet, a 2400 DPI platesetter: these numbers say how finely the machine can place dots. They do not change your file.
Scanner specs. A scanner rated at 600 DPI samples 600 points per inch of the original. That figure becomes pixels in the file, which is why scanning at 600 DPI and printing at 600 PPI are not the same claim.
Trade shorthand. When a print rep asks for '300 DPI images', they mean images that will land at roughly 300 pixels per inch on the page. The word is loose; the intent is PPI.

What DPI does not tell you is whether your picture is sharp enough. An image can carry a DPI tag of 300 in its metadata and still print soft, because that tag is only a suggestion about intended scale.

When to use PPI

PPI is the number that decides whether a photo looks crisp on paper. It is calculated from two things you actually control: the pixel dimensions of the image and the size it is placed at.

PPI = pixel width ÷ placed width in inches

A 3000-pixel-wide photo placed 10 inches wide gives 300 PPI. The same photo stretched to 20 inches gives 150 PPI, which is visibly soft for a glossy brochure and usually fine for a large poster viewed from a few feet away.

Useful working targets:

300 PPI for offset printing, art books and anything read up close
200-300 PPI for most digital press work and photo books
150 PPI for large-format prints viewed at arm's length
72-150 PPI for screen-only output, where print DPI is irrelevant

Why the DPI number stored in an image says little

Open a JPEG's properties and you will often see a resolution field reading 72 or 300. That value is metadata. It records what some camera, phone or editor decided to write, and it changes nothing about how many pixels exist. Delete it and the image is identical. Change it to 600 and the image is still identical.

The only honest way to judge print sharpness is to divide real pixel dimensions by real placed size. That is exactly what PDF Preflight does: it reads the effective PPI of every picture in a PDF at the size it is actually placed on the page, and points out the ones too low for print. If a picture is embedded at 4 inches wide with 800 pixels, you get 200 PPI and a clear warning, regardless of what its metadata claims.

Checking a whole document, not one image

A single photo is easy to reason about. A 40-page catalogue with 90 images is not, because each one sits at a different size. Preflight reports the effective figure per image, so you can fix the two that are under target instead of re-exporting everything at maximum resolution and bloating the file.

If a resolution problem turns out to be a text problem in disguise, PDF Text to Outlines converts type to vector outlines so it renders and prints identically without the fonts installed. For fixing page order or replacing a page before you print, PDF Editor and PDF Merger & Splitter both work on the file directly.

Why doing this locally in the browser beats upload-based sites

Print files are frequently the most sensitive documents a person handles: client brochures, medical leaflets, contracts, unpublished book layouts. Uploading one to a random converter means a copy now exists on someone else's server, under their retention policy, possibly in a jurisdiction you have not thought about.

Alvseike runs entirely in the browser. The PDF is opened locally, read locally and never transmitted. There is no file-size cap, so a 400 MB press-ready PDF is not rejected at the door, and there is no watermark stamped on your proof.

On cost: Alvseike is free to use with no account, metered at 5 runs per day, and a free account raises that to 15 a day. A run is one export, however many files it contains, and free plans process up to 3 files per batch without an account or 5 with one. Pro is $12.99/month, removes the batch cap, unlocks unlimited daily use and covers all 50 Alvseike tools, not just this one. Working offline as an installed app is a Pro feature.

Common mistakes

Trusting the DPI field in metadata. It is a label, not a measurement. Two files with identical pixels can carry different DPI tags and print identically.
Confusing image DPI with printer DPI. A 1440 DPI inkjet does not make a 100 PPI image sharp. Device resolution and image resolution are separate quantities.
Upsampling to hit a number. Resampling a 150 PPI image to 300 PPI adds interpolated pixels, not detail. It doubles the file size and looks no better on paper.
Judging on screen at 100%. A monitor shows a fraction of print resolution. Zoom to the placed size, not to pixel-for-pixel.
Assuming one target fits all. A wall poster at 150 PPI can look excellent; a business card at 150 PPI looks cheap.
Ignoring the placed size. The same image can be perfectly acceptable on one page and unacceptable on another. Effective PPI depends on placement, not on the file alone.

Free for 5 exports a day with no account, or 15 with a free account — and an export can hold several files. Go Pro for unlimited use.