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PPI Calculator

Calculate pixels per inch, compare screen densities, or find the resolution and screen size for your target PPI.

Pixels Per Inch & Pixel Density Calculator

Your measurements

Diagonal shortcuts are measurements, not product recommendations.

Inputs and calculations stay in this browser tab. They are not uploaded, saved or automatically included in feedback. Refreshing clears entries.

Enter the required measurements to see pixel density or a reverse calculation.

How it works

  1. Choose Calculate PPI, Resolution Needed or Screen Size Needed.
  2. Enter custom resolution/size values or use convenience shortcuts. Physical measurements support inches and centimeters.
  3. For Resolution Needed, choose an aspect ratio and target PPI. Other modes derive the ratio from pixel dimensions.
  4. Optionally compare a second screen, review density and pixel pitch, then copy the results.

A real example

Fictional display measurements: 1920 × 1080 at 24 inches gives about 91.79 PPI; 2560 × 1440 at 27 inches gives 108.79 PPI. At 3840 × 2160, a 27-inch screen gives 163.18 PPI, 32 inches gives 137.68 PPI, and 65 inches gives 67.78 PPI.

The 27-inch 4K UHD example has 8.29 megapixels, about 64.24 pixels per centimeter, 0.156 mm pixel pitch, and physical dimensions about 23.53 × 13.24 inches. These are geometry results, not product or viewing-distance recommendations.

PPI, resolution and megapixels

PPI means pixels per physical inch. Resolution counts horizontal and vertical pixels; megapixels count the total pixels divided by one million. The same resolution on a smaller screen has higher density, while its megapixel count is unchanged.

Monitor, TV, phone/display and general image-density calculations use the same geometry when pixel dimensions and physical diagonal are known. The calculator assumes square pixels and the visible image rectangle. It does not include a bezel or device chassis.

PPI vs DPI, PPCM and pixel pitch

People sometimes search for a “DPI calculator” when they mean pixel density. PPI counts digital image/display pixels per inch; DPI technically counts output dots per inch, such as printing dots. They are not interchangeable measurements.

PPCM is pixels per centimeter: PPI ÷ 2.54. Pixel pitch is the physical distance per pixel: 25.4 ÷ PPI millimeters, or 25400 ÷ PPI micrometers. Higher PPI means smaller pixel pitch, without proving that one display looks better. Viewing distance, eyesight, scaling and content also affect perceived sharpness; this tool gives no quality labels or viewing-distance advice.

How the forward and reverse calculations work

Pixel diagonal = √(horizontal pixels² + vertical pixels²), and PPI = pixel diagonal ÷ diagonal inches. The aspect ratio comes from the actual resolution: 1920 × 1080 reduces to 16:9, while 3440 × 1440 reduces to 43:18. No preset ratio is forced onto custom inputs.

Resolution Needed multiplies diagonal inches by target PPI, then divides that pixel diagonal into horizontal and vertical components using your chosen ratio. It shows both theoretical values and nearest whole-pixel rounding, with the density produced by those rounded values. A mathematical resolution need not be sold as a real display.

Screen Size Needed divides pixel diagonal by target PPI, then derives physical width and height from the resolution ratio. Comparison reports density differences neutrally, without ranking overall display quality.

Frequently asked questions

Why do 27-inch and 32-inch 4K screens have different PPI?

Both have the same pixel count at 3840 × 2160. The larger physical rectangle spreads those pixels over more space, so its pixels-per-inch density is lower.

Does this only work with 16:9 screens?

No. Calculate PPI and Screen Size Needed derive the ratio from your resolution. Resolution Needed supports 16:9, 16:10, 3:2, 4:3, 21:9 and a custom positive ratio.

Does higher PPI automatically mean a better-looking display?

No. It is a density measurement. Viewing distance, eyesight, scaling, content and other display characteristics affect perceived image quality. No universal Retina or quality threshold is applied.

How are whole-pixel results rounded?

Resolution Needed rounds each theoretical dimension to the nearest whole pixel and recalculates the resulting PPI and ratio. It does not guarantee that rounding reaches or exceeds your target density.

Can I enter unusually large custom resolutions?

Yes. Resolution dimensions must be positive safe whole integers, up to 9,007,199,254,740,991 per axis. Non-finite, unsafe or zero-pixel results are rejected. Large outputs may use compact scientific notation; there is no device/model database.

Are my screen measurements uploaded or saved?

No. Calculations use browser page memory. Refreshing clears entries. Copy Results uses your clipboard or a manual-copy fallback, and feedback does not automatically include inputs or results.

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