Image tools for printing

Getting an image from a screen onto paper at the right size, shape and sharpness, whether that is a photo lab, a print shop or your own printer.

Resolution

Print sharpness depends on pixels per inch of paper. About 300 is the standard for prints viewed up close.

Change DPISet the DPI tag print software reads, and see the print size at that DPI for each file.
Resize imageScale down oversized images to what the print actually needs, saving upload time.

Getting the shape right

Paper sizes have their own proportions, and a mismatch means the lab crops for you.

Crop imageCrop to 3:2 for 6 × 4, 4:5 for 8 × 10, or type exact pixel sizes for A4 and A3.
Make image squareAdd white borders instead of cropping when nothing can be lost.
Split image into gridSplit a poster into a grid of A4 or Letter sheets to print at home and tape together.

Print-ready files

Print shops often want PDF or TIFF rather than web formats.

JPG to PDFPut images on A4 or Letter pages with margins, ready to print exactly.
TIFF to JPGMake a lightweight preview of a TIFF print file to send for approval.
SVG to PNGRender vector artwork at 4× for high-resolution printing.

Pixels needed for common sizes at 300 DPI

Print	Pixels
6 × 4 in (15 × 10 cm)	1800 × 1200
7 × 5 in (18 × 13 cm)	2100 × 1500
10 × 8 in (25 × 20 cm)	3000 × 2400
A4	2480 × 3508
A3	3508 × 4961

Posters viewed from across a room need far less: 150 DPI is plenty for most wall prints. The reasoning, and a rule of thumb based on viewing distance, is in DPI is mostly a label.

About colour

Everything these tools produce is RGB. Most photo labs and home printers expect RGB and convert to ink themselves. Commercial offset printers may ask for CMYK files, which need a design application with the printer's colour profile. Bright screen blues and greens always calm down a little on paper.

Questions people ask

How do I make an image 300 DPI?

Use the DPI changer. It sets the tag without changing pixels. Check that the image has enough pixels for your print size first.

What shape is a 6 × 4 print?

3:2, the same as most camera photos, so they print without cropping.

Can I print a large poster at home?

Yes. Split the image into a grid and print each tile on a separate sheet.