Screen Dimensions CalculatorFree online other calculator — instant results, no sign-up
Find screen width from diagonal and aspect ratio.
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About the Screen Dimensions Calculator
The Screen Dimensions Calculator finds a rectangular screen’s width in inches from its diagonal measurement and aspect ratio. Enter the diagonal and the width and height components of the aspect ratio to estimate the display’s horizontal size, excluding its bezel or frame.
- Diagonal (in)
- The corner-to-corner measurement of the display area in inches, with a default of 55.
- Aspect width
- The unitless horizontal component of the screen’s width-to-height ratio, with a default of 16.
- Aspect height
- The unitless vertical component of the screen’s width-to-height ratio, with a default of 9.
Formula and method
W = D × a / √(a² + b²); with the default inputs, W = 55 × 16 / √(16² + 9²) = 47.936655 in, rounded to six decimal places.
- WCalculated screen width in inches.
- DScreen diagonal in inches.
- aUnitless aspect width component.
- bUnitless aspect height component.
The calculator treats the screen as a rectangle whose width and height are proportional to the aspect ratio components. By the Pythagorean theorem, the diagonal of that ratio rectangle is √(a² + b²). Dividing the entered diagonal by this value gives a scale factor; multiplying that factor by the aspect width gives the screen width in inches.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Diagonal55 in
- Aspect width16
- Aspect height9
Results
- Result47.936655 in
How to use the Screen Dimensions Calculator
- 1Enter the display’s corner-to-corner diagonal in Diagonal (in); use 55 for the default example.
- 2Enter the horizontal ratio component in Aspect width; use 16 for the default example.
- 3Enter the vertical ratio component in Aspect height; use 9 for the default example.
- 4Check that all three inputs are positive and that the aspect ratio is entered as width to height.
- 5Read the calculated Result: the default inputs produce a screen width of 47.936655 in.
Reading your result
The Result row reports the horizontal width of the display area in inches, not its diagonal, height, or overall device width. With a 55-inch diagonal and a 16:9 aspect ratio, Result = 47.936655 in. The displayed decimal precision describes the calculation, not the accuracy of the physical screen measurements.
Limitations
The calculation assumes a flat, rectangular display and a width-to-height aspect ratio that matches its physical display area. Inputs must be positive. Advertised diagonal sizes may be rounded, and bezels, frames, stands, and mounting clearances are excluded. For curved screens, the result may not represent the straight-line width needed for fitting the device into a space; consult the manufacturer’s dimensions.
Common questions
Why is the width less than 55 inches in the default example?+
The 55-inch measurement is the diagonal, which runs between opposite corners and is longer than either side. At a 16:9 aspect ratio, the calculated horizontal width is 47.936655 in.
Should I enter pixel dimensions as the aspect width and aspect height?+
You can use pixel width and pixel height as the ratio components when the screen has square pixels. Only their proportion matters; the inputs do not need to be reduced to their simplest ratio.
Can I use this width to check whether a television fits in a cabinet?+
Use it only as an estimate of the display area’s width. Check the manufacturer’s overall television dimensions and required ventilation clearances before deciding whether it fits.
How do I enter the aspect ratio for a portrait-oriented screen?+
Enter the ratio components in their current width-to-height order. For the default screen rotated into portrait orientation, enter 9 as Aspect width and 16 as Aspect height, keeping the diagonal at 55 inches.
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.