Digital Image Resolution Converter

Convert between dot/inch (DPI), pixel/inch (PPI), dot/millimeter, and other digital image resolution units with scientific precision.

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Digital Image Resolution Units Explained

Dot per Inch (DPI)

A unit of image resolution measuring the number of individual dots of color per linear inch. 1 DPI = 1 dot/inch. Commonly used for printer specifications and print media.

Common uses: Printer specifications, scan resolution, print quality standards, and photographic print standards.

Pixel per Inch (PPI)

A unit of image resolution measuring the number of individual pixels per linear inch. 1 PPI = 1 pixel/inch. More commonly used for digital display specifications.

Application: Screen resolution specifications, digital photography display, monitor specifications, and web image optimization.

Dot per Millimeter (dot/mm)

A metric unit of image resolution. 1 dot/mm ≈ 25.4 DPI. Used in international and metric-based printing and digital specifications.

Application: European printing standards, scientific imaging, microscopy image capture, and metric system documentation.

Dot per Meter (dot/m)

A metric unit equal to 1 dot/m = 0.001 dot/mm. Very fine resolution measurement used for precision digital imaging.

Application: High-precision imaging, scientific research, archival standards, and detailed digital documentation.

DPI vs PPI: Understanding the Difference

While often used interchangeably, DPI and PPI have distinct meanings. DPI refers to physical printed dots on paper from a printer or printing press. PPI refers to pixels displayed on a digital screen or captured by a camera sensor.

Key distinction: DPI is output-dependent (printer capability), while PPI is inherent to the digital image file and display device. A digital image with 72 PPI will look sharp on a monitor but will be too low resolution for quality printing.

Resolution Standards & Recommendations

  • Web images: 72 PPI standard (modern screens: 96-220 PPI actual)
  • Standard computer monitors: 96 PPI (older CRT monitors were 72 PPI)
  • High-density displays (Retina): 220+ PPI for sharp text and images
  • Smartphone screens: 300-500+ PPI for crisp display
  • Standard office printing: 300 DPI minimum for acceptable quality
  • Photo printing: 600-1200 DPI for professional quality
  • Magazine/brochure printing: 1200-2400 DPI for highest quality
  • Document scanning: 200 DPI adequate for reading; 300+ DPI for archival
  • Newspaper printing: 300-600 DPI (halftone screening at 150 LPI)
  • T-shirt screen printing: 300-600 DPI for detailed designs

Important Resolution Considerations

  • Upscaling limitation: You cannot improve image quality by simply increasing DPI/PPI; this is called upscaling and results in blurry images
  • Downsampling: Reducing resolution (downsampling) can be done without significant quality loss if done properly
  • Monitor display: Screen displays show actual pixel size; a 1920×1080 image always has the same pixel count regardless of stated PPI
  • Print output: Printer quality depends on both resolution and print head technology; higher DPI doesn't always mean better quality
  • File size: Higher resolution images create larger file sizes; balance quality needs with storage and bandwidth constraints
  • Optical vs digital zoom: Optical zoom (lens-based) preserves quality; digital zoom interpolates pixels and may reduce quality