Pixel Ruler — PPI, Print Size & Resize Calculator

PPI (pixels per inch) describes screens — how many pixels are packed into one inch of display. DPI (dots per inch) describes printers — how many ink dots are placed in one inch of paper. In practice, the terms are often used interchangeably for digital files (a '300 DPI' photo file really means '300 PPI when printed') even though it's technically loose.

300 PPI at final print size is the gold standard for photo prints, magazines, and fine art. 150 PPI is acceptable for newspapers, posters, and anything viewed from more than 6 feet away. Below 150 PPI, you'll see pixelation in a normal photo print. Large prints (24×36 inches and up) can get away with 100–150 PPI because viewers stand further back.

Apple's marketing term for displays with pixel density high enough that individual pixels are not visible at typical viewing distance. The threshold varies with viewing distance: ~218 PPI for a 27" iMac (3 ft viewing), ~264 PPI for an iPad (1.5 ft viewing), ~326 PPI for an iPhone (1 ft viewing). Other manufacturers call equivalent screens HiDPI or 4K UHD.

Traditional bicubic/bilinear scaling above ~150% softens detail. For better results, use AI upscalers like Topaz Photo AI, Adobe's Super Resolution (in Camera Raw), or free options like Upscayl. These reconstruct plausible detail rather than just stretching pixels. The honest rule: never assume an upscaled image has the detail of a native shot.

Web images are sized in pixels because the display defines physical size at view time. Print images are sized in inches because the printer defines pixel-to-paper mapping. The same 1920×1080 file looks crisp on a phone (small physical size, high PPI) and pixelated on a 24-inch monitor (large physical size, lower effective PPI). For print, always think in physical dimensions plus DPI.