Start with the file, not the printer label
Before ordering a print, note the image’s actual pixel dimensions and the size you want on paper. Those two pieces of information answer a more useful question than the resolution number stored in the file: how many source pixels will occupy each printed inch?
PPI means pixels per inch of image. DPI means dots per inch produced by a printing device. A printer can use several dots to reproduce a pixel’s tone or color, so its advertised DPI is not a pixel requirement for your photo. Do not multiply your paper size by a printer’s 1,200 DPI specification to decide how large the image must be.
Try the numbers before changing the image
Suppose your landscape image is 3,600 × 2,400 pixels. At 12 × 8 inches, each axis supplies 300 PPI. At 18 × 12 inches, the same file supplies 200 PPI. No pixels have disappeared; you are distributing them over a larger piece of paper.
A 300 PPI target would call for 5,400 × 3,600 pixels at 18 × 12 inches. Resizing the original to those dimensions adds estimated pixels. It may be useful for a delivery requirement, but it cannot recreate texture that the camera never captured. Keep an untouched original and inspect the resized result before paying for the full print.
A resolution label is not extra detail
Changing a file’s resolution metadata from 72 to 300, while keeping its pixel dimensions, changes the suggested physical size. It does not sharpen the underlying picture. Print software may follow that metadata, ask for a different size, or apply its own fit-to-page setting.
Use 300 PPI as a planning reference when appropriate, rather than a pass stamp. A close-viewed portrait, a large poster viewed across a room, and a diagram with small text have different demands. Focus, compression damage, paper, printer settings, and viewing distance still matter. Confirm the provider’s requirements, calculate density after any crop, then make a small test print when the result matters. A numerical check helps prevent mistakes; it cannot replace seeing the print.
Current capabilities and limits
At 150 PPI, a 10 × 8 inch print needs 1500 × 1200 pixels. Without resampling, a 1800 × 1200 image at 300 PPI prints at 6 × 4 inches. This mode ignores paper dimensions, margins and crop.
Enable Keep pixel dimensions. JPG, PNG, BMP and TIFF store the selected density. The export is still re-encoded; it does not preserve all metadata or create missing detail. Other formats do not store the selected PPI.