What is DPI?
DPI — DPI (Dots Per Inch) measures print resolution — how many ink dots a printer places per inch of physical output. For screens, the equivalent measure is PPI (Pixels Per Inch). 300 DPI is the standard for professional print; 72 or 96 DPI is the historical screen standard.
DPI stands for Dots Per Inch and describes the output resolution of printed material — how many individual ink dots a printer can place within one linear inch. Higher DPI means finer detail is reproduced in print. At 300 DPI, individual dots are invisible to the naked eye at normal reading distance, making it the professional print standard for books, magazines, and fine art prints.
DPI is often confused with PPI (Pixels Per Inch), which measures screen pixel density. A 4K monitor at 27 inches has approximately 163 PPI; an iPhone 15 Pro has 460 PPI. Digital images do not have an inherent DPI — the DPI value stored in image metadata (the EXIF/JFIF pHYs chunk) is a recommendation for printing software, not a property of the pixel data itself.
Changing an image's DPI metadata does not change the image's pixel count. To print an image larger without loss of quality, you must either increase the pixel dimensions (upscale) or reduce the print size to stay within the printer's resolution.
DPI vs PPI: The Correct Terminology
DPI is strictly a printer measurement (ink dots per inch). PPI is the screen measurement (pixels per inch). In everyday usage, 'DPI' is incorrectly used to mean PPI — you will often see '72 DPI for web' or '300 DPI for print' even when referring to digital files. The confusion persists because early publishing software conflated the two terms. When setting up images for print, the relevant value is the ratio of pixel dimensions to intended print size, which determines the effective PPI at print.
DPI Requirements by Print Type
300 DPI: professional print (books, magazines, brochures, fine art). 150 DPI: acceptable for large-format posters viewed at distance (A1, A0). 72–96 DPI: screen display (web, presentations). At 300 DPI, a 1200×1600 pixel image prints at 4×5.3 inches. At 150 DPI, the same image prints at 8×10.6 inches. Reducing DPI increases print size without changing pixel count — and vice versa.
DPI Tools on PicsSizer
Frequently Asked Questions
How do I change the DPI of an image?▾
PicsSizer's DPI Changer modifies the DPI metadata in JPEG (JFIF APP0 segment) and PNG (pHYs chunk) files without resampling the pixel data. This tells printing software to render the image at your specified DPI. It does not add or remove pixels — if you need more pixels, use the resize/upscale tool instead.
Does changing DPI affect image quality?▾
Changing only the DPI metadata (without resampling) does not change any pixel data and therefore does not affect image quality. The pixel count stays identical. Only when you physically resample the image (change pixel dimensions) does quality change.
What DPI should I use for web images?▾
DPI is irrelevant for web images. Browsers display images at 1:1 pixel ratio — one image pixel per screen pixel (or more on high-DPI screens via CSS). The DPI metadata in web images is ignored by browsers. For web optimization, focus on pixel dimensions and file size, not DPI.