Image dimensions, resolution, and DPI for web and print

A 1600 x 900 image contains that pixel grid regardless of the DPI value in its metadata. On the web, the browser displays it at a CSS size determined by layout.

For an 800 CSS-pixel slot, an 800-pixel source may be sufficient on a standard display. A 1600-pixel version can look sharper on a 2x display, at the cost of more transfer bytes.

PPI connects pixel count to physical size. A 3000-pixel image printed at 300 ppi spans 10 inches on that side. Printing it smaller increases density without creating pixels.

Adobe presents 300 ppi as a common reference for high-quality prints viewed closely, while noting that large formats viewed from a distance may use less. DPI concerns the output device.

Multiply physical size in inches by target ppi. To convert centimeters to inches, divide by 2.54.

Example: a 15 cm wide print at 300 ppi needs about 1772 pixels. This is a planning target; paper, printer, viewing distance, and content also affect the result.

Aspect ratio links width and height. If you set width only, the converter calculates matching height. Disabling that link and forcing incompatible values stretches or squashes the image.

Downsampling removes pixels and is generally predictable. Upsampling makes an algorithm estimate new pixels: the grid grows, but no real detail is recovered.

For web and email, start from the largest displayed width and add a denser variant only when sharpness justifies it. For print, start from physical size and the density required by the provider.

Some Canvas-created outputs carry a default resolution value in metadata. That does not change their pixel count. Verify print size in the destination software when it is contractual.