Is this image large enough to print? Check effective PPI

To check whether a raster image has enough pixels for a print job, divide its pixel width by the width it will occupy on the finished piece, measured in inches. That result is its effective PPI. A 3,000-pixel image placed 10 inches wide has 300 effective PPI; place the same image 20 inches wide and it has 150.

Start with the final printed size

Measure the image where it will actually print, not the overall page. A photograph covering half a flyer is evaluated at that photograph’s placed size. If the printer will enlarge a supplied layout, include that enlargement. When a file is cropped, check the pixel dimensions of the portion that remains; discarded pixels cannot contribute detail to the print.

Keep the original image file linked to the layout. Adobe notes that a pasted preview can have less usable data than the original placed image, and that scaling beyond the image’s native size reduces effective PPI in InDesign. In that app, select the image, open Window → Links, and read Effective PPI in Link Info. The number reported for the source file alone is not enough once the image has been resized.

Calculate effective PPI

Use pixel width ÷ printed width in inches. For millimetres, convert first: inches = millimetres ÷ 25.4. You can enter your own values in the print-size calculator.

If the image is scaled unevenly, calculate width and height separately and use the lower result for the direction with less detail. A vector logo is different: its paths can scale without a fixed pixel grid, although any bitmap inside the vector file still needs checking.

Decide whether the result is suitable

There is no single PPI pass mark for every job. Adobe gives 150–300 PPI or more as a commercial-print range that depends on press and screening, and tells readers to consult their prepress provider. A close-viewed photo book, a garment transfer and a large sign viewed across a room are different decisions. Ask the receiving printer for the required effective resolution at final size.

The number also cannot tell whether the source is sharp. Motion blur, compression blocks, heavy noise reduction and a low-quality image enlarged by software can all produce a disappointing result at a high pixel count. Inspect the actual details that matter—faces, small text, product edges and fine texture—at the intended output size, then use a proof when the job warrants it. Printer DPI describes output dots and is not interchangeable with an image’s effective PPI.

What to do when detail is limited

1. Look for the original capture, scan or export. A social-media download or a screenshot may be much smaller than the source.
2. Reduce the placed size if the design permits. Halving the printed width doubles effective PPI without inventing pixels.
3. For logos, lettering and flat shapes, request an editable vector source when possible. Rebuilding a small raster logo as vector art is different from resampling it.
4. If you try image upscaling, compare the result with the original at final size. Extra pixels can smooth an image or invent plausible detail; they do not prove the original information was recovered.
5. When the available file is still marginal, tell the customer or operator before output and agree on a proof or revised size.

Check the exported file

Review the image in the final PDF at its placed size. Confirm the export has not substituted a low-resolution proxy or downsampled it more than the job allows. Adobe’s print-ready PDF workflow includes low-resolution images among the issues to resolve before production. Use the full preflight checklist for fonts, bleed, colour and page geometry as well.

For a mixed-artwork sheet, calculate resolution for each raster design at its own final size before it is imposed. The gang sheet preparation guide covers the other checks at that stage.