Pixels, Resolution and DPI: What Actually Matters for Images
Separate screen dimensions from print density so you can resize images with the right target in mind.
Pixels describe digital dimensions
An image that is 3000×2000 contains six million pixels regardless of what DPI metadata says. On a screen, CSS/layout determines how large those pixels appear.
DPI/PPI matters when mapping pixels to physical size
For print, 3000 pixels at 300 pixels per inch corresponds to roughly 10 inches. Change the print size and the effective pixel density changes.
Changing DPI metadata alone may not add detail
If you change a file from 72 DPI to 300 DPI without resampling, the underlying pixel count can remain identical; only the intended print-size metadata changes.
Use destination requirements
A website may specify 1200×630 pixels. A printer may specify physical inches plus a target PPI. Follow the requirement that matches the medium.
Keep masters large
Downsize delivery copies for speed while preserving the original high-resolution image for future crops and print work.
A task you can work through
A 3000 by 2000 photo contains six million pixels. At 300 pixels per inch it can cover approximately 10 by 6.67 inches without resampling; at 150 pixels per inch it covers about 20 by 13.33 inches. The pixel data has not changed in either calculation. On a website that displays the photo at 600 CSS pixels wide, an appropriate source width also depends on the display density and cropping behavior.
Where this approach fails
Changing a DPI metadata field from 72 to 300 does not manufacture new camera detail. Enlarging a small source interpolates pixels; it may smooth visible blocks but cannot recover letters that were never legible. Printers can also have specific bleed, crop and color requirements beyond pixel density. The site’s Resize Image tool changes pixel dimensions; it is not a print-preflight service.
Check the result before using it
Determine the physical size and required pixels per inch from the printer, multiply them to get a target pixel dimension, and compare it with your source. For screen use, check the destination’s required pixel dimensions. View the output at 100% and as an actual print proof when quality matters.
Calculate before changing metadata
For a 6-inch-wide print at 300 pixels per inch, you need approximately 1800 source pixels across the crop. A 1200-pixel image gives 200 pixels per inch at that size; changing its DPI label to 300 does not create the missing 600 pixels. For a website requesting 1200 by 630, those exact pixel dimensions matter more than a DPI tag. Determine crop and output medium first, then resize copies while retaining the original.
Try the related tool
Change image dimensions precisely. The tool page explains its implementation and limitations. Keep your original and inspect any important result.
Resize Image →Technical references
These external references explain the underlying formats or browser APIs. The worked examples above describe this site's specific tool behavior.