Pixel Density CalculatorFree online other calculator — instant results, no sign-up
Calculate pixels per inch from resolution and diagonal.
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About the Pixel Density Calculator
The Pixel Density Calculator calculates a display’s pixels per inch (PPI) from its horizontal resolution, vertical resolution, and diagonal size in inches. It helps you compare how tightly pixels are packed on screens of different sizes and resolutions. With the default inputs of 3840 horizontal pixels, 2160 vertical pixels, and a 27-inch diagonal, the result is 163.178309 PPI.
- Horizontal pixels
- The number of pixel columns across the display’s active width, measured in pixels.
- Vertical pixels
- The number of pixel rows along the display’s active height, measured in pixels.
- Diagonal (in)
- The corner-to-corner distance across the active display area, excluding the bezel, measured in inches.
Formula and method
PPI = √(H² + V²) / D; with the default inputs, PPI = √(3840² + 2160²) / 27 ≈ 163.178309.
- PPIPixel density, measured in pixels per inch.
- HHorizontal resolution in pixels.
- VVertical resolution in pixels.
- DActive display diagonal in inches.
The calculator uses the Pythagorean theorem to find the diagonal pixel distance, then divides that distance by the physical diagonal in inches. For the default inputs, 3840² + 2160² = 19,411,200; taking the square root and dividing by 27 gives 163.178309 PPI when rounded to six decimal places.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Horizontal pixels3840
- Vertical pixels2160
- Diagonal27 in
Results
- Result163.178309 PPI
How to use the Pixel Density Calculator
- 1Enter the display’s native horizontal resolution in Horizontal pixels; the default is 3840.
- 2Enter its native vertical resolution in Vertical pixels; the default is 2160.
- 3Enter the active screen diagonal in Diagonal (in); the default is 27.
- 4Check that the resolutions and diagonal describe the same display area and that all values are positive.
- 5Read the calculated PPI result; the default inputs produce 163.178309 PPI.
Reading your result
The Result row reports pixel density in PPI. A result of 163.178309 PPI means approximately 163.18 pixels fit along one inch of the display horizontally or vertically, assuming square pixels. Higher PPI means smaller, more closely packed pixels, but perceived sharpness also depends on viewing distance and the content being displayed.
Limitations
The calculation assumes a rectangular display with square, uniformly spaced pixels and a diagonal measurement that matches the active pixel area. Use native panel resolution to estimate physical pixel density; a lower operating-system output resolution does not change the panel’s actual pixel count. Advertised diagonal sizes may be rounded, so six decimal places in the result do not imply equivalent measurement accuracy. PPI alone does not describe brightness, contrast, subpixel layout, or overall image quality.
Common questions
Should I use native resolution or the resolution selected in display settings?+
Use the panel’s native resolution for physical PPI. A lower selected resolution is typically scaled to the native pixel grid and does not change the panel’s physical density.
Does the 27-inch diagonal include the bezel?+
No. The diagonal should measure the active display area from corner to corner, not the outer enclosure or bezel.
Will swapping 3840 and 2160 change the PPI?+
No. The formula squares and adds both resolutions, so swapping them leaves the result unchanged. Rotating the same display does not change its pixel density.
Does display scaling change the calculated PPI?+
No. Display scaling changes the size of text and interface elements in physical pixels, not the panel’s native resolution or diagonal. The default display remains 163.178309 PPI regardless of interface scaling.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
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Results are estimates for informational purposes and are not financial, medical or legal advice.