Image PPI (Pixels Per Inch) Calculator
Calculate pixel density (PPI) from pixel dimensions and a physical diagonal, with a print-quality rating and maximum print sizes at 150 and 300 PPI. Runs in your browser.
Result
- Diagonal resolution
- 4405.81 px
- PPI (pixels per inch)
- 163.18
- Dot pitch
- 0.16 mm
- Max print @ 300 PPI
- 12.8 × 7.2 in
- Max print @ 150 PPI
- 25.6 × 14.4 in
Print quality at this size: Acceptable — okay for larger prints viewed at a distance
About this tool
Pixels per inch (PPI) measures how densely pixels are packed into a physical area — the higher the number, the sharper the image looks. This calculator takes a pixel width and height plus a physical diagonal in inches and computes PPI the standard way: it finds the diagonal in pixels (the Pythagorean combination of width and height) and divides by the diagonal in inches. It also reports the dot pitch (millimeters per pixel) and, for print work, the largest size you can output while keeping a given density — 300 PPI for crisp photographic prints and 150 PPI for larger pieces viewed from a distance. A quality rating summarizes whether the resolution is comfortable for print at the size implied. The 300 PPI benchmark comes from the roughly 300 dots-per-inch the human eye can resolve at typical reading distance; signage viewed from meters away needs far less. All math runs locally.
How to use it
- Enter the image's pixel width and height.
- Enter the physical diagonal in inches (the screen or intended print diagonal).
- Read the PPI, dot pitch, and the maximum print sizes at 300 and 150 PPI.
- Use the quality rating to decide if the resolution is enough.
Frequently asked questions
- What is the difference between PPI and DPI?
- PPI (pixels per inch) describes a digital image or display; DPI (dots per inch) describes how many ink dots a printer lays down. They are often used interchangeably, but strictly PPI is the image's resolution and DPI is the printer's output density. For sizing prints, PPI is the number you control.
- How is PPI calculated?
- PPI = (diagonal in pixels) ÷ (diagonal in inches), where the diagonal in pixels is √(width² + height²). For a 3840×2160 image on a 27-inch diagonal, that is √(3840²+2160²) ÷ 27 ≈ 163 PPI.
- Why is 300 PPI the standard for printing?
- At a normal reading distance of about 30 cm, the human eye resolves roughly 300 dots per inch, so 300 PPI prints look continuous-tone and sharp. Going much higher rarely helps; large-format prints viewed from farther away look fine at 150 PPI or even less.
- What does dot pitch tell me?
- Dot pitch is the physical size of one pixel (25.4 mm ÷ PPI). Smaller dot pitch means a finer, sharper display. It is the same density expressed as a length rather than a count.
- How big can I print my photo?
- Divide each pixel dimension by your target PPI. A 6000×4000 photo at 300 PPI prints up to 20×13.3 inches; at 150 PPI it stretches to 40×26.7 inches with lower density. The tool shows both thresholds.
- Is my image uploaded?
- No image is uploaded — you enter only the pixel dimensions and physical size, and all math runs in your browser.