Why does 8K have 16 times the pixels compared to 1080p?

Question

Considering 2K = 1440p, has twice the pixels compared to 1080p, 4k has four times as many, why does 8k not follow this trend?

Answer 1

First off, 2K is not 1440p, it is 2048 x 1080p. 4K is 4096 x 2160p. (Note that UHD = 3840 x 2160p...4K and UHD are like US and Canadian dollars--they are both dollars, but they have different values.)

It's simple math: when you have a straight line and you make it twice as long, the new length is 2x the original length. When you have a rectangular area and you double both the length and the width in order to keep the same aspect ratio, the new area = (2L) * (2W) = 4 * (L*W)

When you double something twice, you do it again:

2*(2L) * 2*(2W) = 4 * 4 * (L*W) = 16 * (L * W)

Answer 2

8K = 8000 x 8000, if 1:1. But you normaly have 16:9 for videos which is 7680 * 4320, since 7680 ≈ 8000, the width is rounded to 8K, if 9:16 aspect ratio, then the height is rounded to 8K.

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7680 * 4320 = 33177600 which is 33MegaPixels, since 33177600 ≈ 33 Million Pixels.

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33 / 4 ≈ 8. 8MP is 4K when 16:9 aspect ratio. Since 3840×2160 = 8294400 ≈ 8 Million pixels. The reason it's Mega is because Mega is a greek word and means 10^6 which is Million.

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So 1080p is easy since 1920 x 1080 ≈ 2MP. Since 2 073 600 is ≈ 2 Million.

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What is then 2MP x 16? It's 32MP. 8K on an 16:9 Aspect ratio is ≈ 33MP, but on an 2:1 Aspect ratio it would be 32MP, since 8K x 4K would be 32 Million.

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Let's do a final calculation.

8K x 4K (8K) = 32MP.

4K x 2K (4K) = 8MP.

2K x 1K (2K, at 16:9 it's called 1080p) = 2MP.

2 x 4 = 8

8 x 4 = 32.

4 x 4 = 16.

So 16 times since you multiply the width with 4 and the height with 4.

(x4) * (y4). at 2K with aspect ratio of 16:9: x would be width, so x is 1920, y would be height, so y is 1080.

(1920 * 4) * (1080 * 4)= 7680 * 4320 = 33177600 ≈ 33MP

So as you can see 7680 * 4320 is called 8K.

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https://en.wikipedia.org/wiki/8K_resolution