Formula and method
A diagonal and aspect ratio form a right triangle. The calculator scales the ratio triangle until its hypotenuse matches the diagonal, then converts the result into inches, centimeters and millimeters.
Assumptions and limits
- The advertised diagonal measures the visible rectangular image area.
- The screen is flat and uses square pixels.
- Bezels, stands and rounded corners are not included.
Worked examples
55-inch 16:9 television
55 × 16 ÷ √337 = 47.94 inches wide. The height is 26.96 inches, or about 121.8 × 68.5 cm.
27-inch 4K monitor
A 27-inch 16:9 panel is 23.53 × 13.24 inches. At 3840 × 2160 pixels, its density is about 163.18 PPI.
Common 16:9 screen dimensions
| Diagonal | Width | Height |
|---|---|---|
| 24 in | 20.92 in / 53.1 cm | 11.77 in / 29.9 cm |
| 27 in | 23.53 in / 59.8 cm | 13.24 in / 33.6 cm |
| 32 in | 27.89 in / 70.8 cm | 15.69 in / 39.8 cm |
| 43 in | 37.48 in / 95.2 cm | 21.08 in / 53.5 cm |
| 55 in | 47.94 in / 121.8 cm | 26.96 in / 68.5 cm |
| 65 in | 56.65 in / 143.9 cm | 31.87 in / 80.9 cm |
| 75 in | 65.37 in / 166.0 cm | 36.77 in / 93.4 cm |
| 85 in | 74.08 in / 188.2 cm | 41.67 in / 105.8 cm |
Frequently asked questions
Does screen size include the bezel?
No. Screen size normally refers to the diagonal of the active display area, not the frame or stand.
Why are two 27-inch monitors different widths?
They may use different aspect ratios. A 16:9 and a 21:9 screen can share the same diagonal but have different widths and heights.
Can I use this for TVs, monitors and projector screens?
Yes. The geometry is the same for any rectangular screen as long as you know the diagonal and aspect ratio.
Why does the calculator ask for aspect ratio?
A diagonal alone is not enough to determine width and height. The aspect ratio defines the shape of the rectangle.