PDF to Grayscale Converter

Colour pages cost more to print and some offices, courts and exam boards ask for black-and-white submissions. This converter renders every page of your PDF and rebuilds it in shades of gray, or in pure 1-bit black and white for the smallest files and the crispest photocopies. Everything happens in your browser, so the document never leaves your device.

How to use this tool

1. Drop one or more PDF files.
2. Choose Grayscale for photos and charts, or Black & white for text documents.
3. Pick a resolution: 150 DPI suits most documents, 300 DPI suits fine print.
4. For black and white, adjust the threshold if thin text breaks up; then download the new PDF and check the page 1 preview.

Formula

Gray = 0.299 × R + 0.587 × G + 0.114 × B

These are the ITU-R BT.601 luma weights: green looks brightest to the eye and blue darkest, so a pure blue heading becomes a dark gray rather than a light one. In black-and-white mode a pixel becomes white when its gray value is at or above the threshold (50% = 127.5) and black below it.

Example

A 3-page flyer with a red title (R 220, G 38, B 38) converts the title to gray 0.299 × 220 + 0.587 × 38 + 0.114 × 38 ≈ 92 — a dark gray that still stands out. At 150 DPI an A4 page becomes a 1240 × 1754 pixel image; in black-and-white mode it is stored with 1 bit per pixel, which is why text-only documents often shrink to a few dozen KB per page.

What changes in the file

The pages are rebuilt as images at the resolution you pick, so the result looks the same everywhere and prints without colour, but its text is no longer selectable or searchable and links and form fields are not kept. If you need searchable text afterwards, run the result through OCR. Very large pages are rendered at a slightly lower resolution so the browser does not run out of canvas memory.