Screen Diagonal Calculator
Calculate screen diagonal size from the physical width and height.
How to use Screen Diagonal Calculator
1. Enter Screen Width, Screen Height, Size Unit. 2. Choose inches, cm or mm and use that same unit for every physical screen dimension. Results keep the selected unit. The active screen is an ideal rectangle; bezels and curved-screen geometry are excluded. 3. Select Calculate or press Enter. 4. Select Copy result to copy the answer, or Reset to clear the form and result.
Why use this tool?
Choose inches, cm or mm and use that same unit for every physical screen dimension. Results keep the selected unit. The active screen is an ideal rectangle; bezels and curved-screen geometry are excluded.
How the calculation works
Diagonal inches = square root(width inches² + height inches²). Choose inches, cm or mm and use that same unit for every physical screen dimension. Results keep the selected unit. The active screen is an ideal rectangle; bezels and curved-screen geometry are excluded. Counts and dimensions use the declared rounding convention; other numbers display up to three decimal places where applicable. Nonzero subsecond durations are labelled. Durations round to the nearest second; nonzero subsecond durations are labelled. File-size output units are decimal. Changing an input label does not convert filled values.
Example
Worked example: Screen Width = 3; Screen Height = 4; Size Unit = "inches". Result: 5 in.
Practical tip
Check the input labels and assumptions against the screen diagonal task before reusing the number.
Frequently asked questions
What exactly does Screen Diagonal Calculator calculate?
Diagonal inches = square root(width inches² + height inches²).
Which units or counting rules apply?
Choose inches, cm or mm and use that same unit for every physical screen dimension. Results keep the selected unit. The active screen is an ideal rectangle; bezels and curved-screen geometry are excluded.
Does this inspect, change or upload my files?
This page calculates the entered values or text in the browser. Numeric image/media tools do not transform files. Check the worked example and stated counting basis; the result does not certify device, search-engine or accessibility outcomes.