Device Pixel Ratio Calculator

Calculate device pixel ratio for screen with Device Pixel Ratio Calculator using the values that apply to your situation. Enter Physical Pixel Width and CSS Pixel Width, and the calculator uses those values to show device pixel ratio. Use it while handling screen to avoid repeating several small conversions or calculations manually. Real devices, networks and software can add limits or overhead that are not represented by a simple numerical input. Before acting on an important result, review the inputs once more so the device pixel ratio reflects the situation you actually want to plan. Read the worked example on the Device Pixel Ratio Calculator page if you want to check how the entered values lead to device pixel ratio before using your own figures.

How to use Device Pixel Ratio Calculator

To use Device Pixel Ratio Calculator, start with the values that apply to your screen case. Enter the value for Physical Pixel Width, then enter the value for CSS Pixel Width. Run the calculation to see device pixel ratio, then compare the answer with the values you entered before using it. Use valid colour or encoding values within the range requested by the tool. Before relying on an important answer, review the entered values once more so device pixel ratio reflects the situation you actually want to calculate. The worked example on the Device Pixel Ratio Calculator page can help you confirm how the inputs should be entered before you calculate your own case. Use the actual source values where possible rather than rounded guesses, especially when a small input change could noticeably affect device pixel ratio.

Why use this tool?

Use Device Pixel Ratio Calculator when screen requires a small digital calculation that would otherwise mean converting several units by hand. It gives you a consistent result for comparing files, screens, images, text or transfer settings. Because the calculation is based on Physical Pixel Width and CSS Pixel Width, you can see which values need to change when you want to test another case. Because Device Pixel Ratio Calculator focuses only on screen, you can change one input at a time and see how that affects device pixel ratio without changing the basis of the comparison. This also makes Device Pixel Ratio Calculator practical for checking more than one screen option, because each run uses the same calculation and the same input definitions.

How the calculation works

Device Pixel Ratio Calculator divides physical pixels by CSS pixels on the same axis. Physical Pixel Width and CSS Pixel Width are the numerical values used by the formula, so they should all describe the same case you want to calculate. Values outside the valid range or format are rejected rather than silently changed into something else. The result gives device pixel ratio from the digital values entered, providing a consistent basis for comparing files, screens, media or transfer settings. When the answer matters, review the source values once more before relying on device pixel ratio, especially if one input was estimated.

Example

For example, enter Physical Pixel Width = 1920 and CSS Pixel Width = 1080. The calculated result is 1.7778. This works by dividing physical pixels by CSS pixels on the same axis, which gives the displayed device pixel ratio.

Practical tip

For Device Pixel Ratio Calculator, use the real values for Physical Pixel Width and CSS Pixel Width rather than rounded guesses when a small input change could affect the answer. Keep the same units and assumptions whenever you compare two results from this tool. Keep the same unit convention when comparing two screen cases so differences in device pixel ratio are not caused by mixing bits, bytes, pixels or time units. Keep the source values alongside device pixel ratio if you may need to check the calculation again later.