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DPI Calculator – PPI, Print DPI & Screen Density

Calculate screen PPI, print DPI, dot pitch, and retina distance instantly from any resolution.

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What is the DPI Calculator – PPI, Print DPI & Screen Density?

DPI Calculator does what most online tools split across three pages: it calculates screen PPI, print DPI, and the perfect size for any resolution — instantly and privately in your browser.

Unlike cluttered calculators, you get:

  • One-click presets for iPhone, Galaxy, MacBook, 4K monitors and more
  • Three modes: Screen PPI, Print DPI, and Reverse (find diagonal for a target PPI)
  • Real metrics: PPI, PPCM, PPI², dot pitch in mm/inches, megapixels, aspect ratio, Android density bucket, and retina viewing distance
  • Print-ready check: see immediately if your image hits 300 DPI, 240 DPI, or needs upscaling

No uploads, no lag with large resolutions. Everything runs client-side, so your data never leaves your device.

How it works

The core formula

For screens, PPI (pixels per inch) is:

PPI=width∗px2+height∗px2diagonal_inPPI = \frac{\sqrt{width*{px}^2 + height*{px}^2}}{diagonal\_{in}}

That is diagonal pixels divided by diagonal inches【9176213441099474269†L74-L78】.

What the tool does

  1. Screen PPI mode
  • Enter width, height in pixels and diagonal (inches or cm)
  • We calculate diagonal pixels with the Pythagorean theorem, then PPI
  • Derive: PPCM = PPI / 2.54, dot pitch = 25.4 / PPI mm, PPI² = PPI × PPI, total megapixels, simplified aspect ratio
  1. Print DPI mode
  • Enter image pixels and desired print size
  • DPI X = width px / width in, DPI Y = height px / height in
  • Effective DPI = min(DPI X, DPI Y). 300+ = print-ready, 240+ = good, 180+ = acceptable
  1. Reverse mode
  • Give a target PPI (e.g., 220 for Retina, 300 for print)
  • We return the diagonal you need: diagonal = diagonal pixels / target PPI

Extra insights

  • Density bucket follows Android definitions: LDPI 0-120, MDPI 120-160, TVDPI 160-213, HDPI 213-240, XHDPI 240-320, XXHDPI 320-480, XXXHDPI 480-640【9176213441099474269†L118-L131】
  • Retina distance ≈ 3438 / PPI inches — the distance where pixels become invisible
  • Dot pitch is the center-to-center pixel distance, shown in both mm and inches【1126124543178570763†L52-L58】

Examples

27-inch 4K Monitor PPI

Find pixel density for a common desktop display

Width: 3840px, Height: 2160px, Diagonal: 27"
 
PPI: 163.18, Dot pitch: 0.156mm, Density: TVDPI (160-213)

Print 300 DPI Check

Verify if a photo is print-ready

Image: 6000×4000px, Print size: 20" × 13.33"
 
Effective DPI: 300, Quality: Print-ready (300+ DPI)

Find Size for Target PPI

What diagonal gives you 220 PPI?

Resolution: 2560×1600, Target PPI: 220
 
Needed diagonal: 13.86" (35.2 cm)

Frequently asked questions

What is the difference between DPI and PPI?

PPI measures screen pixel density (pixels per inch). DPI measures printer dots per inch. The math is identical, but DPI is for print and mouse sensitivity, PPI is for displays. They are often used interchangeably for screens【9176213441099474269†L82-L86】.

How do you calculate PPI?

  1. Find diagonal pixels: √(width² + height²)
  2. Divide by diagonal inches Example: 1920×1080 on a 24" screen → √(1920²+1080²)=2202.9 → 2202.9/24 = 91.79 PPI【9176213441099474269†L63-L78】.

What is PPI² and why show it?

PPI² is pixels per square inch (PPI × PPI). It tells you how many pixels fill a 1-inch square, useful for comparing sharpness. A 220 PPI screen has 48,400 pixels per square inch【1126124543178570763†L36-L42】.

What is a good PPI for monitors, phones, and TVs?

  • Phones: 400-500+ PPI (XXHDPI-XXXHDPI)
  • Laptops: 220-260 PPI (XHDPI)
  • Desktop monitors: 90-160 PPI is typical; 160-213 is TVDPI, 213-240 is HDPI【9176213441099474269†L118-L126】
  • TVs viewed from 6-10 ft: 40-80 PPI is fine

Is 300 DPI really required for printing?

Yes for high-quality photo prints. 300 DPI means 300 dots per inch, the standard for sharp prints. 240 DPI is good, 180 DPI is acceptable for large posters viewed from distance.

How is dot pitch calculated?

Dot pitch = 1 / PPI inches, converted to mm (×25.4). For a 163 PPI 4K 27" monitor, dot pitch = 0.156 mm【1126124543178570763†L56-L58】.

Can I find what screen size I need for a target PPI?

Yes. Use Reverse mode. Enter resolution and target PPI — the tool returns diagonal = diagonal pixels / PPI. For 2560×1600 at 220 PPI, you need a 13.86" display.

Why does my phone look sharper than my 4K monitor?

Pixel density, not resolution alone. A 6.1" phone at 2556×1179 is ~460 PPI (XXXHDPI), while a 27" 4K monitor is ~163 PPI. Higher PPI packs more pixels into each inch.

Do you support centimeters?

Yes. Toggle units and we convert automatically (1 inch = 2.54 cm). The underlying PPI formula always uses inches.

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