DPI vs. PPI
Also known as: Dots per inch vs. pixels per inch
What Is the Difference Between DPI and PPI?
PPI (pixels per inch) describes a digital image: how many of its pixels fill each inch once it’s printed or shown at a given size. DPI (dots per inch) describes a printer: how many dots of ink it lays down in each inch of paper.
Print shops often say DPI when they mean PPI. When a printer asks for a 300 DPI file, it wants 300 pixels for every inch of the finished print. CE.SDK uses the same wording, so its DPI setting decides how many pixels per inch an export gets.
What Is PPI?
PPI is a property of the image file. It follows from two things: how many pixels the image has, and how large it prints. The same photo has a high PPI as a small print and a low one as a poster.
Typing a higher PPI into an image’s settings adds no pixels. It only changes the size the file says it should print at, so the detail has to be there from the start.
What Is DPI?
DPI is a property of the printer. To reproduce one pixel’s color, a printer can place several tiny dots of ink, the idea behind halftone printing.
Printer DPI can’t add detail the file doesn’t have. That part comes down to the PPI of the artwork.
How Much Resolution Does a Print Need?
Most prints need about 300 PPI at the size they print, but large prints seen from a distance can use less. What matters is how close people look.
Up close
Printed pieces people hold, like photos and flyers, look detailed at 300 PPI even with your nose up to them.
Across a room
Large posters and banners seen from a meter or more away usually look sharp at 150 to 180 PPI.
From far away
Billboards work at a small fraction of that, because the eye can’t pick out fine detail from far down the road.
How to Calculate Print Size From Pixels
Divide each side of the image, in pixels, by the PPI the print needs, and you get the largest size it prints at that quality.
Pixels ÷ PPI = inches
A photo 3,000 pixels wide prints 10 inches wide at 300 PPI.
PNG, JPG or WebP. The image stays on your device.
Largest print size at 300 PPI
How Many Pixels Do Common Print Products Need?
At 300 PPI, a US business card needs 1,050 × 600 pixels and a US Letter flyer needs 2,550 × 3,300. Large posters and banners can drop to 150 PPI. The sizes below are finished sizes, so add the printer’s bleed on every side.
| Finished size | Resolution | Pixels needed | |
|---|---|---|---|
| Business card (US) | 3.5 × 2 in | 300 PPI | 1,050 × 600 |
| Business card (EU) | 85 × 55 mm | 300 PPI | 1,004 × 650 |
| Postcard | 4 × 6 in | 300 PPI | 1,200 × 1,800 |
| Flyer (US Letter) | 8.5 × 11 in | 300 PPI | 2,550 × 3,300 |
| Flyer (A4) | 210 × 297 mm | 300 PPI | 2,480 × 3,508 |
| Small poster | 11 × 17 in | 300 PPI | 3,300 × 5,100 |
| Large poster | 36 × 48 in | 150 PPI | 5,400 × 7,200 |
| Roll-up banner | 850 × 2,000 mm | 150 PPI | 5,020 × 11,811 |
How to Set Print Resolution in CE.SDK
Design in inches or millimeters
For a web-to-print design tool, set the scene’s unit to inches or millimeters and give each page its print size, so the layout matches the finished print.
Set the DPI
Set the DPI to the resolution the printer asks for, usually 300.
Export
An image export gets the pixels that follow from the page size and the DPI, or an exact width and height if you set one. In a PDF, the DPI decides the resolution of photos and rasterized effects, and the page size stays the same.
Print Resolution in Photo Prints and Signage
Photo prints
A photo print product sets its scenes to 300 DPI in inches, so an 8 × 10 print exports at 2,400 × 3,000 pixels.
Posters and banners
A signage tool sets its large-format templates to a lower DPI, which keeps files manageable for prints people see from across a room.
Links
Documentation and references for this concept.
Web-to-Print Design Tool
Warn customers when an image is too small for the print size they picked.
Design Units Guide
Set up scenes in inches or millimeters and choose the DPI used at export.
Export to PDF
How the DPI setting controls image resolution in an exported PDF.
Export to PNG
Export an image at an exact width and height in pixels.
Photo Prints
Build a photo print product, from in-app editing and smart layouts to print-ready export.
Design Validation Demo
See the editor flag images that fall below a minimum resolution.
Related Terms
Design Unit
The measurement system used to define all dimensions, positions, and sizes within a scene: either Pixel, Millimeter, or …
Export
The process of rendering one or more pages of a CE.SDK scene to a distribution-ready file, supporting PNG, JPEG, WebP, T…
PDF/X
An ISO-standardized subset of PDF designed for reliable, predictable reproduction in professional print production, enfo…
Halftone
The printing technique that turns photos into tiny ink dots of varying size, so a press that can only print ink or no in…
Print Resolution
How many pixels of an image land in each inch of paper once it prints, usually requested as 300 DPI. CE.SDK's scene DPI …