Screen Size Comparison Calculator
Screens are sold by the diagonal, which is the one dimension nobody needs. Worse, the diagonal only means something once you know the shape: a 34 inch ultrawide and a 34 inch 16:9 monitor are different objects. And a 55 inch screen is not twice the picture of a 27 inch one — it is nearly four times the area.
What this generator does
Splits the diagonal into a width and a height in the aspect ratio's proportion, converts to centimetres, works out the picture area, and derives the pixel density from the resolution.
How to use this tool
- Type the diagonal of each screen and choose its shape.
- Add the pixels across if you want the density as well.
- Read the real width and height in centimetres.
- The comparison is by area, which is what your eyes actually see.
Understanding the controls
- Diagonal in inches
- The size the screen is sold as, corner to corner. On its own it does not tell you the width, which is why the shape matters too.
- Shape
- 16:9 for most televisions, 21:9 or 32:9 for ultrawides, 16:10 and 3:2 for many laptops, 4:3 for older screens. Two screens of the same diagonal in different shapes have different areas.
- Pixels across
- The horizontal resolution, if you want the pixel density. Zero leaves it out. The vertical count follows from the aspect ratio.
Common use cases
- Checking whether a television will fit the space it is going in
- Comparing an ultrawide monitor against a normal one at the same diagonal
- Seeing how much bigger the picture really gets going up a size
- Working out pixels per inch before buying a monitor
- Knowing how close you can sit before the pixels show
How this generator works
The diagonal, the width and the height form a right triangle whose sides are in the aspect ratio, so the width is the diagonal times the ratio's width over its hypotenuse. The check runs that backwards: the width and height are put through Pythagoras and must give the diagonal back, and their ratio must be the aspect ratio it started from. The comparison between two screens is by picture area rather than by diagonal, because area is what you see — doubling the diagonal at the same shape quadruples the picture, which the check states explicitly. Pixel density is pixels over inches of width, and the viewing distance shown is where one pixel subtends about a minute of arc, the usual rule for where pixels stop being visible.
Randomness and fairness
Nothing is random. The same diagonal and shape always give the same dimensions.
For how randomness is produced across the whole site, see how Generate Random works.
Limitations and good to know
- This is the panel, not the product: bezels, stands and frames add to what actually has to fit.
- Curved screens measure their diagonal along the curve, so the flat width is slightly less than shown.
- The viewing distance is a rule of thumb about acuity, not a recommendation about comfort.
- Marketing sizes are often rounded; the exact panel may be a fraction under.
Privacy and your data
The comparison is worked out in your browser. No screen sizes are transmitted or stored.
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