Screens show colour by mixing red, green and blue light (RGB, and sRGB is the standard colour space for the web), while printers mix cyan, magenta, yellow and black ink (CMYK). Some bright screen colours, especially vivid blues, greens and neon tones, cannot be printed with CMYK ink, so they come out duller on paper. Use sRGB for everything on screens (websites, social media, email), and for printing ask your print shop what they need: many accept RGB and convert it themselves, others want CMYK PDFs at 300 DPI at the final print size.
- RGB is light, CMYK is ink. They do not cover the same colours.
- sRGB is the safe default for any image shown on a screen.
- For print, check what the printer wants before converting.
- Print needs enough pixels: about 300 DPI at the final size.
- Prepare files with the free Image Converter and cropper.
The bright blue that turned purple
A coaching centre designs a gorgeous electric-blue banner on a laptop. On screen it glows. They send the file to a print shop in Nilkhet for 500 leaflets. The leaflets come back a dull, slightly purple blue, and the owner thinks the printer cheated him.
Nobody cheated. The colour on his screen simply does not exist in printer ink. A quick soft-proof before printing, or choosing a slightly different blue, would have avoided the surprise.
RGB vs CMYK
| RGB / sRGB | CMYK | |
|---|---|---|
| Works by | Adding light (red, green, blue) | Ink absorbing light (cyan, magenta, yellow, black) |
| Used for | Screens: websites, phones, TV, social media | Printing: leaflets, cards, banners, packaging |
| Colour range | Wider for bright, saturated colours | Narrower; neon and very vivid colours dull down |
| File formats | JPG, PNG, WebP, most image files | PDF, TIFF, some JPG; set in design software |
What is sRGB and why use it online?
Colour spaces define exactly which red, green and blue your numbers mean. sRGB is the standard for the web and most screens. Cameras and design apps may use wider spaces such as Adobe RGB or Display P3; if you upload those without converting, some browsers and apps show colours washed out or oversaturated. Exporting as sRGB keeps colours consistent for almost everyone.
Preparing images for print
- Ask the printer firstDo they want RGB or CMYK? PDF or JPG? Which paper and size? Do they need bleed (extra margin that gets trimmed)?
- Check resolutionFor sharp prints, aim for about 300 pixels per inch at the final size. An A4 page (8.3 x 11.7 inches) needs about 2480 x 3508 pixels.
- Convert colours if askedUse design software (Photoshop, Affinity, Illustrator, or free tools like Scribus or GIMP with plugins) to convert to the printer’s CMYK profile.
- Soft-proofPreview how colours will look in CMYK. Adjust vivid colours that shift too much.
- Add bleed and safe marginsKeep text away from the edges.
- Order a proofFor big runs, print one copy first and check it in daylight.
Quick pixel guide for common print sizes at 300 DPI
| Print size | Pixels needed |
|---|---|
| Business card (3.5 x 2 in) | 1050 x 600 |
| Photo 4 x 6 in | 1200 x 1800 |
| Photo 5 x 7 in | 1500 x 2100 |
| A4 leaflet | 2480 x 3508 |
| A3 poster | 3508 x 4961 |
Printing AI-generated images? See how to print AI images at the right resolution.
Common mistakes
- Printing images downloaded from social media (too small and compressed).
- Choosing neon colours for print without checking a proof.
- Converting to CMYK when the printer wanted RGB and does the conversion better themselves.
- Uploading CMYK JPGs to websites, where some browsers show strange colours.
Related guides
For logos that scale to any size, read what is an SVG file. Need to combine scans for printing or forms? See how to convert photos to PDF.
Sources
Frequently asked questions
What is the difference between RGB and CMYK?
RGB creates colour with light on screens. CMYK creates colour with ink on paper. CMYK cannot reproduce some bright RGB colours.
Should I use sRGB for websites?
Yes. sRGB is the standard colour space for the web and gives the most consistent colours across devices.
Do I need to convert to CMYK before printing?
Ask your printer. Many accept RGB and convert it themselves; others require CMYK PDFs with specific settings.
What resolution do I need for printing?
About 300 pixels per inch at the final print size for close-viewed items. Large banners can use less.
Why did my bright blue print look dull?
Very vivid screen colours are outside the CMYK range, so printers reproduce the nearest possible ink colour, which looks duller.
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