Direct answer. In PrintExactly, switch to a custom size, type the dimensions in mm, cm, or inches, verify the printable area and effective DPI, and print at 100% scale.

The 3-step method

  1. Enter the exact dimensions in any unit. Open PrintExactly, leave the preset dropdown on Custom, and enter a positive width and height in mm, cm, or inches, up to 2,000 mm per side.
  2. Match the paper and printer. Set the document page size to match the loaded paper. The active Mac printer's printable area is read directly into the workspace.
  3. Verify and print at 100%. Confirm effective DPI for the custom size, that the photo is fully inside the printable area, and that 100% scale is requested. Press when ready to the.

Common pitfalls at custom sizes

  • Image too small for the chosen custom size. Effective DPI falls when you print a low-resolution source at a large custom size. PrintExactly surfaces the effective DPI so you can shrink the target or upgrade the source.
  • Borderless expansion. Borderless mode shifts printed size by 1–2%. Switch to a bordered paper size for exact custom-size output.

Frequently asked questions

Can I use millimeters, centimeters, and inches for custom photo sizes?

Yes. PrintExactly accepts custom widths and heights in mm, cm, or inches up to 2,000 mm per side. The workspace converts internally and reports effective DPI for each item.

What is the largest custom photo size I can print on Mac?

There is no software cap. The practical limit is your source image resolution and the active printer's maximum paper size.

Print a photo at exact size on Mac · Full exact-size Mac guide