Pixels set the detail budget
A 1200 × 1800 image contains 2.16 million pixels whether its metadata says 72, 300, or 600 DPI. Those pixels carry the visible samples. Changing a resolution tag can change the suggested physical size, but it cannot recover texture, edge detail, or focus that the file never captured. A 72 DPI tag does not shrink the file or lower its pixel dimensions. A 300 DPI tag does not sharpen it. Both tags only affect the requested scale.
Start every print check with pixel width and height. Cropping removes pixels. Resampling can create more output pixels, but those estimates are not new source detail. Keep the original and judge any enlarged copy at the intended print size.
PPI and printer DPI describe different stages
People often say DPI for both image resolution and printer output. For the image calculation, pixels per inch is the clearer term: it tells you how many image pixels map to one printed inch. Printer DPI describes the device's ink or toner dots, which is a different mechanism.
Adobe uses 300 PPI as a common target for sharp, close-viewed prints and notes that large prints viewed from farther away can work at lower image resolution. [1] Treat 300 as a planning target, not a promise that every printer, paper, subject, and viewing distance needs the same number.
Calculate print size before changing metadata
Divide each pixel dimension by the target PPI. At 300 PPI, 1200 ÷ 300 gives 4 inches and 1800 ÷ 300 gives 6 inches. A 2400 × 3000 image gives 8 × 10 inches. If the required print is larger, choose a lower PPI target, obtain a larger source, or resample a copy and inspect the result.
PNG stores physical resolution in the optional pHYs chunk as pixels per unit; the standard uses metres when the unit is known. [2] Exif defines resolution fields for formats that carry Exif metadata. [3] These fields describe scale. The pixel dimensions remain separate.
Change DPI metadata only after the pixels are ready
Use the Image Size Checker to read the exported file's pixel dimensions first. Calculate whether they support the planned print. Then use Set Image DPI to write the requested resolution metadata and review the print-size estimate.
For native PNG and JPEG inputs, imgrove changes the supported DPI metadata without re-encoding the compressed pixels. Other browser-readable formats convert to PNG, so keep the source. The receiving print shop or upload form still decides which format, dimensions, profile, and resolution it accepts.
Use 300 PPI as a planning target when
- Preparing small or medium prints viewed at close range
- Checking whether a camera file has enough pixels for a requested size
- Writing resolution metadata after pixel dimensions are final
Check a different requirement when
- A print provider gives an exact PPI, size, profile, or file-format rule
- A large display will be viewed from farther away
- The source is soft or heavily compressed despite having enough pixels
Related reading
Related imgrove tools
Set DPI after you verify the pixels
Check the image dimensions, write a DPI value from 1 to 2400, and review the calculated print size in your browser. The tool does not claim to add detail.
Try Set Image DPITry the workflow and tell us what worked, what failed, or what needs clearer guidance: hi@imgrove.com.