PixelSpec

851 x 315 pixels

851 x 315 px is a 2.7:1 landscape size, the Facebook cover photo size. 851 divided by 315 is 2.7016, and dividing both by their greatest common divisor, 1, reduces the fraction exactly to 851:315, which is rounded to 2.7:1 in practice. It is 0.27 megapixels (268,065 pixels) with a diagonal of 907 px.

Who uses 851 x 315

Platform image sizes that are exactly 851 by 315 pixels
PlatformAssetRoleSource
FacebookCover photoRecommended sizeDocumented

851x315 vs 315x851

315x851 is the same two numbers swapped, and that makes it a different shape: 1:2.7 portrait instead of 2.7:1 landscape. Width is always written first, so 851x315 is 851 pixels wide and 315 tall, while 315x851 is 315 wide and 851 tall. As decimals that is 2.7016 against 0.3702. Cropping one to fill the other keeps only 13.7 percent of the picture, so the two are not interchangeable.

No platform size in this dataset is 315x851: every use listed above is 851 wide by 315 tall. If an export meant for one of them comes out as 315x851, the two numbers were entered the wrong way round.

What the numbers mean

The pixel count is what the file stores. It is not the size the image appears at on a screen, and the two get confused constantly. A display measures its layout in CSS pixels, and most phones draw two or three physical pixels for every CSS pixel. That device pixel ratio is why an avatar that occupies 110 CSS pixels wants a file several times wider: on a 2x screen those 110 CSS pixels are 220 physical ones, and a 110 px file gets upscaled to fill them.

So 851 by 315 is a statement about the file, not about how large it looks. Whether it is enough depends on the largest surface it has to fill and on the pixel ratio of the screen filling it, which is why the platform pages above carry a minimum width as well as a recommended size.

Resize an image to 851 x 315

Preloaded to this exact size. It runs in your browser, so nothing is uploaded anywhere.

Drop images, paste, or click to browse
Preloaded to 851 by 315 for 851 by 315. Add one file or several. Everything runs in your browser.

Keep the 851x315 shape at another size

Preloaded with 851:315, the exact ratio of 851 by 315. Type a new width or height and the calculator solves the other side, so the shape stays identical.

Common ratios

Type in either the width or the height and the other side solves to keep the ratio.

851:315 at 851 px wide

851 x 315px

The height is 315 px.

height = 851 x 315 / 851 = 315 px.

Ratio
851:315
Decimal
2.7016
Result ratio
851:315

Starting from other numbers? Open 851 x 315 in the aspect ratio calculator to find the ratio of any width and height.

Questions about 851x315

Is 851x315 2.7:1?
Not exactly, but close. The greatest common divisor of 851 and 315 is 1, so the exact ratio is 851:315, which is 2.7016 as a decimal. 2.7:1 is the rounded label used for this shape, 0.06 percent away from the exact value.

Closest other sizes

Nearest by shape, so a crop between any of these loses the least. Sorted by how far each one is from 2.7016.

Discord profile banner680x240Twitch profile banner1200x480X (Twitter) header1500x500Bluesky banner1500x500Eventbrite event banner2160x1080

Every size on one page: the cheat sheet. Last verified 2026-07-27.