Save a page of text as PNG at 300 dpi. In our test that file came out smaller than the JPG of the same page, 793 KB against 873 KB for a page of a NIST report, and it keeps every letter edge exact. The usual advice, JPG for small files and PNG for quality, only holds at lower resolutions, and it falls apart completely on photos, where PNG was more than nine times bigger.
Four pages, three sharpness settings, two formats
We ran four pages through our PDF to JPG and PDF to PNG tools on 24 September 2026: a page of text and a table from a NIST report made in Word, a page from the “Attention Is All You Need” paper with its architecture diagram, the first page of the IRS W-9 form, and a photo placed on a page with our JPG to PDF tool. The tools draw each page with pdf.js and save it with the browser’s own encoder, JPG at quality 90.
| Page | 72 dpi JPG | 72 dpi PNG | 150 dpi JPG | 150 dpi PNG | 300 dpi JPG | 300 dpi PNG |
|---|---|---|---|---|---|---|
| Report page, text and a table | 114 KB | 139 KB | 340 KB | 367 KB | 873 KB | 793 KB |
| Paper page with a diagram | 82 KB | 121 KB | 270 KB | 328 KB | 732 KB | 825 KB |
| IRS W-9, page 1 | 165 KB | 197 KB | 545 KB | 548 KB | 1.41 MB | 1.36 MB |
| Photo page (2200×1200 at 150 dpi) | 141 KB | 1.34 MB | 517 KB | 2.55 MB | 1.62 MB | 3.41 MB |
On the three text pages, PNG cost between 0.4% and 48% more at 72 and 150 dpi, and at 300 dpi it was smaller on two of the three. Our reading of why comes down to how each format fails. JPG is built for smooth photographs; around every sharp black-on-white letter it spends bytes on faint ripples, and a page at 300 dpi has a lot of letter edges. PNG compresses long runs of identical white pixels well, and a higher resolution gives it longer runs. The photo page has neither advantage for PNG: every pixel differs from its neighbour, and PNG stores them all.
So our rule for page images is short. Text, forms, slides, charts and diagrams go to PNG. Pages that are mostly a photo go to JPG. If a page mixes both, like a brochure, JPG is safer on size and the text will still read well at 150 dpi or more.
Which dpi to pick
Dots per inch here means how many pixels each inch of the page becomes. A Letter page at 72 dpi is 612 pixels wide. At that size the body text of the NIST report is readable on a laptop at 100%, but there is nothing to zoom into; enlarge it and the letters turn soft and blocky. 150 dpi, 1275 pixels wide, is what we would use for slides, chat and web pages. 300 dpi is for printing and for anyone who needs to read small print on a phone by pinching in.
Each step up roughly triples the file: the report page went from 114 KB to 340 KB to 873 KB as JPG. A 40-page PDF at 300 dpi as PNG can pass 30 MB, past Gmail’s 25 MB limit for attachments.
If you only need the words
A page image is a picture: its text can’t be searched or copied. When what you want is the text itself, PDF to text gives you a few kilobytes instead of megabytes, and our notes on PDF text extraction cover where that goes wrong.