Why TV Screens Are Measured Diagonally?

If someone suddenly asks you,

‘Hey, why TV screens measured diagonally?’

What would your answer be? Do you actually know the exact reasons behind this?

Well, this question is somewhat underrated, and approximately 99% of smart TV users don’t know the answer.

In this article, I will break down this matter in detail so that you can gain a clear understanding of why TV screens are measured in this manner.

Let’s move on…

Why do we measure TV screens diagonally?

  • Diagonal measurement provides the most accurate representation of a screen’s size.
  • It accounts for both the horizontal and vertical dimensions.
  • It’s an industry-standard method for comparing screens of different aspect ratios.
  • Helps consumers easily compare TV sizes across brands and models.
  • Reflects the viewing experience better than other measurements like width or height.


Here are the detailed explanations:

Reason 1: Historical Evolution

historical evolution of Why TV screens are measured diagonally
© Homespoiler.com /AI

To understand why TV screens are measured diagonally, we need to travel back in time to the early days of television.

In the early days of television, screens were almost exclusively square.

This created a challenge when trying to convey screen size, as a simple width or height measurement wouldn’t suffice. With the transition from cathode-ray tubes to flat screens, the question of how to describe screen size became even more pressing.

Interestingly, film industry played a significant role in the adoption of diagonal measurements.

Movie screens were traditionally measured diagonally, and this practice naturally carried over to television. It was a practical solution, as it provided a single number that could convey the overall size of the screen.

Reason 2: Aspect Ratio

aspect ratio measurements of a TV
© Homespoiler.com /AI

Aspect ratios play a significant role in the need for diagonal measurements.

Different TVs have different aspect ratios.

For instance, older TVs typically had a 4:3 aspect ratio, while modern HDTV displays often feature a 16:9. There are also cinematic or ultra-wide screens with a 21:9 aspect ratio.

Measuring diagonally allows for a consistent way to compare the sizes of TVs with varying aspect ratios.

It shows the size of the visual experience rather than focusing only on the height or width dimensions.

Reason 3: Marketing and Consumer Perception

Consumers are often drawn to larger diagonal measurements.

Consumers are often drawn to larger diagonal measurements.

It’s a psychological phenomenon; a 50-inch TV sounds more impressive than a 45-inch one, even if the difference in actual screen area is not substantial.

Manufacturers understand this psychological quirk and use it to their advantage.

When people walk into a TV store, they are often immediately drawn to the TVs with the largest diagonal measurements, influencing their purchasing decisions.

This preference for larger diagonals has led to misconceptions.

People may think a bigger diagonal means a better TV, which isn’t always the case.

Reason 4: Comparison with Other Devices

Comparison with Other Devices
© 123rf.com

Measuring screens diagonally is not just for TVs; it’s a common way to measure screens on various devices.

This standard makes it easier for both manufacturers and consumers to compare screen sizes.

Think about all the electronic gadgets we use daily: computer monitors at work, pocket-sized smartphones, tablets for work and fun, and even small smartwatch screens. Despite their differences, they all use the same method to measure screen size—diagonally.


Using this same measurement helps manufacturers tell us how big their device screens are in a way everyone can understand.

This consistency makes communication clear and lets consumers choose the right screen size for their needs.

Whether you need a bigger TV screen or a smaller smartphone for convenience, measuring diagonally helps you compare and pick the perfect screen size.


Q: Why are TV screens measured diagonally and not horizontally or vertically?

TV screens are measured diagonally because it gives an easy and consistent way to say how big the screen is.

Whether it’s an old-style TV or a modern one, measuring from one corner to the opposite corner shows its size.

This makes it simple to compare TVs, no matter their shape.

Q: Do all TVs have the same aspect ratio?

No, TVs come in various aspect ratios, and diagonal measurements allow for fair comparisons across these different ratios.

Q: Why did circular picture tubes determine early TV sizes?

Circular tubes limited the size of early TVs, and measuring the tube’s diameter accurately estimated the screen’s surface area.

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