Screen Size Calculator
A screen's size is its diagonal, so it does not tell you how wide or tall it is. Enter the diagonal and the shape, and this works out the width and height in inches and centimeters.
How do you work out width and height from the diagonal?
Use the aspect ratio and Pythagoras. A 16 by 9 rectangle has a diagonal of 18.36, so a 16:9 screen is the diagonal × 16 ÷ 18.36 wide. Its height is the diagonal × 9 ÷ 18.36.
So a 27 inch 16:9 monitor is 23.5 in (59.8 cm)59.8 cm (23.5 in) wide and 13.2 in (33.6 cm)33.6 cm (13.2 in) tall.
Why are two 27 inch screens not the same size?
The diagonal is the same, but the shape is not. A 27 inch 21:9 ultrawide is 24.9 in (63.3 cm)63.3 cm (24.9 in) wide and 10.4 in (26.5 cm)26.5 cm (10.4 in) tall. That makes it wider but shorter than a 27 inch 16:9 screen.
The squarer the shape, the more screen area you get for the same diagonal.
What are the width and height of common 16:9 screens?
These are the visible screen only. Laptops run from 13.3 to 17.3 in (34 to 44 cm), and TVs from 43 in (109 cm) up.
How big is a home cinema screen?
Projector screens are sold by the diagonal too, and the shape matters just as much. At the two most popular sizes:
- 100 inch: 87.2 in221.4 cm × 49.0 in124.5 cm at 16:9, or 92.3 in234.3 cm × 38.6 in98.0 cm at the 2.39:1 cinema shape
- 120 inch: 104.6 in265.7 cm × 58.8 in149.4 cm at 16:9, or 110.7 in281.2 cm × 46.3 in117.6 cm at the 2.39:1 cinema shape
A 2.39:1 screen of the same diagonal is wider but much shorter. To match the height of a 16:9 screen, it needs a larger diagonal. The projector screen size calculator adds the throw distance.
What are the dimensions of a 4:3 screen?
4:3 is the easy one. Its sides are in the ratio 3, 4 and 5, so the width is 0.8 times the diagonal and the height 0.6 times. A 15 inch 4:3 screen is 12.0 in30.5 cm × 9.0 in22.9 cm.
Older TVs, office monitors and many tablets use 4:3, and so do most phone camera photos.
Can I work out a phone screen size?
Yes, with the width and height mode. Phones use tall shapes such as 19.5:9 that are not in the ratio list. Measure the lit screen across and up, enter both, and the calculator gives the diagonal and the ratio.
Why does the calculator need the aspect ratio?
Because one diagonal fits many shapes. A square and a long, thin rectangle can share a diagonal, yet the square has far more area. The aspect ratio fixes the shape, so width and height follow from it.
How do I measure a screen with a tape measure?
Measure the visible picture from one corner to the opposite corner, leaving out the frame. Then measure its width and height the same way. Enter the width and height above to check the diagonal and the shape.
Questions
Is screen size measured diagonally?
Yes. The size in the name is the diagonal of the visible picture, corner to corner. The frame around it is not included.
Why is my measurement a little smaller than the size on the box?
Makers round the diagonal to a whole or half inch. TVs are often sold by size class, so the measured diagonal can be a little under the number in the name.
How do I find the size of the screen I am using now?
Hold a bank card against the screen on our monitor size page and match the outline. It works out your diagonal, width and height in about 20 seconds.
How big is a 14 inch 16:10 laptop screen?
11.9 in (30.2 cm) wide and 7.4 in (18.8 cm) tall. Pick 16:10 above for any laptop with 1920 × 1200 or 2560 × 1600 pixels.
How we measure
Width = diagonal × a ÷ √(a² + b²) and height = diagonal × b ÷ √(a² + b²), where a:b is the aspect ratio. Going the other way, the diagonal is √(width² + height²).