PDF File Size Calculator: Dimensions, DPI and Bleed

Estimate PDF file size before and after compression, standard ISO print dimensions with 3mm bleed, and email limits.

PDF file size by page format, DPI and bleed

A page's pixel size is its size in inches × the resolution: A4 at 300 DPI is 2,480 × 3,508 px. The raw weight is then pixels × bytes per pixel (4 for CMYK, 3 for RGB, 1 for greyscale) × number of pages, and the tool applies a compression rate: 10 A4 pages in CMYK at 300 DPI come to about 18 MB.

Calculation

  • Final size = format + 2 × bleed if the option is ticked (3 mm on each side by default).
  • Pixels = size in mm ÷ 25.4 × DPI, rounded.
  • Raw weight = pixels × bytes per pixel × pages (4 for CMYK, 3 for RGB, 1 for greyscale, 0.125 for 1-bit line art), in MB of 1,048,576 bytes.
  • Estimated weight = raw weight × 5.5% for standard compression, × 2% for high compression, × 100% uncompressed, with a minimum of 0.08 MB per page.

Example

10 A4 pages in CMYK at 300 DPI: 2,480 × 3,508 px per page, 331.9 MB raw, about 18.25 MB with standard compression. With 3 mm of bleed the page becomes 216 × 303 mm, i.e. 2,551 × 3,579 px and about 19.16 MB. At 14 pages the file reaches 25.55 MB and the tool flags it as over 25 MB. The same document in RGB with high compression weighs about 4.98 MB.

Assumptions

  • Each page is treated as a full-page image. A PDF of text and vector drawings is far lighter, a few tens of KB per page.
  • The 5.5% and 2% compression rates are averages: flat colour compresses better than a photo.
  • The prepress table lists common printer requirements: 300 DPI, 2 to 5 mm of bleed, CMYK for paper.

This tool estimates a file you are about to produce. For office printing costs, use the print cost calculator; to hide a logo or watermark in an existing PDF, use the watermark removal tool.

Sources and dates: A sizes per ISO 216:2007; US Letter (8.5 × 11 in), Legal (8.5 × 14) and Tabloid (11 × 17); Gmail attachment limit of 25 MB for personal accounts, with Google Workspace accounts following the limit set by their administrator (Gmail Help, checked 14/10/2026).

Frequently Asked Questions

How many pixels is an A4 page at 300 DPI?

2,480 × 3,508 pixels: 210 mm ÷ 25.4 × 300 and 297 mm ÷ 25.4 × 300, rounded. At 150 DPI the same page is 1,240 × 1,754 px, and at 72 DPI 595 × 842 px.

How much bleed should I add for a printer?

Most printers ask for 3 mm on each side, sometimes 2 to 5 mm. An A4 page then grows from 210 × 297 mm to 216 × 303 mm, which is 2,551 × 3,579 px at 300 DPI.

Why is my PDF too large to email?

Pages scanned or exported as CMYK images weigh the most: 10 A4 pages at 300 DPI come to about 18 MB with standard compression, and 14 pages exceed Gmail's 25 MB attachment limit. Switching to RGB with high compression brings 10 pages down to about 5 MB.

Should I export a PDF in CMYK or RGB?

CMYK for offset or digital printing at a print shop, RGB for on-screen use. CMYK stores 4 bytes per pixel against 3 for RGB, so at the same size the raw file is a third heavier.

Is this tool really free?

Yes, all tools on Kristools are 100% free and accessible without registration.

Is my data protected?

Yes. All processing is performed directly and securely inside your browser. No personal data is sent to our servers.