What DPI actually means (and which number to pick)

For a PDF page exported as an image, start at 150 DPI and inspect the smallest text. Try 300 DPI if you need a detailed print or more room to zoom. For a photo going on a website, check its pixel dimensions and file size first; a DPI label alone will not make it sharper.

Two settings that look alike

Changing an image’s resolution label tells software how large to print the existing pixels. Without resampling, the image data stays the same. A 3000-pixel-wide photo can print 10 inches wide at 300 pixels per inch, or 20 inches wide at 150 pixels per inch.

Rendering a PDF at a chosen resolution creates new pixels from the page. A higher setting gives text and vector drawings a finer grid to be drawn on. Embedded photographs and scans are still limited by the detail in their source images.

Strictly, PPI is pixels per inch in an image, while DPI is dots per inch produced by a printer. Export tools often use “DPI” for raster image resolution, including the PDF tools here. A printer’s advertised dot resolution is not the pixel resolution you need to supply.

Pick a starting point for the task

Task	Starting point	What to check
Small page thumbnail	72 or 96 DPI	Can you identify the page?
Page image for screen reading	150 DPI	Small text at the intended display size and zoom
Detailed page image or ordinary print	300 DPI	Fine lines, labels and the printer’s requirements
Scan for OCR	Around 300 PPI at capture	Recognition accuracy, language and scan clarity
Photo for a web upload	Required width and height in pixels	Destination limits and the saved file size

These are starting points, not quality standards. A poster viewed from a distance and a page of tiny technical drawings need different treatment. For commercial print or an archive, use that service’s specifications.

Exporting PDF pages with ToolsNow

In PDF to images, Resolution controls how many pixels are created. The default is 150 DPI. Choose JPEG for a photographic page or PNG when you want lossless encoding of the rendered pixels, then use Render & download. Each selected page downloads separately.

For an A4 page, these are approximate dimensions, rounded to the nearest pixel. A PDF’s exact page box and the renderer’s rounding can change them slightly.

Resolution	Approximate A4 image size
72	595 × 842 px
96	794 × 1123 px
150	1240 × 1754 px
200	1654 × 2339 px
300	2480 × 3508 px

Doubling the resolution gives four times as many pixels, since both width and height double. It does not promise a fourfold change in compressed file size; content, format and quality settings affect that too.

Compressing a PDF is a separate decision

The PDF compressor defaults to 96 DPI and 80% JPEG quality. That setting may be too low for small print or faint scans. Check the downloaded pages and increase the resolution if needed.

This compressor makes picture-only pages. It discards existing searchable text and OCR layers, regardless of the DPI you choose. Keep the original when those features matter. A higher resolution does not preserve them.

For ordinary photos, image compression lets you adjust quality and pixel dimensions. Use the receiving site’s size requirements rather than trying to reach a particular DPI number.

How the size calculation works

Use this when you know the final print size:

pixels needed = print size in inches × pixels per inch

A 6 × 4 inch print at 300 PPI needs 1800 × 1200 pixels. For centimetres, divide each dimension by 2.54 before multiplying.

The familiar 72 and 96 settings do not describe every modern screen. Browsers, displays and zoom settings can map an image to different numbers of screen pixels. Judge the result at its intended size, rather than treating either number as a universal screen resolution.

Last reviewed 2 October 2026.