A Facebook cover photo is 851×315 pixels — an unusually wide 2.7:1 strip that matches nothing else on the platform. The complication is that it is never displayed at 2.7:1. Facebook fits the image into containers of two different shapes depending on the device, so the crop you see while uploading on a laptop is not the crop your visitors on phones get.
Why 851 × 315?
851×315 is the size Facebook itself names: its help page says a cover photo loads fastest as an sRGB JPG file that is 851 pixels wide, 315 pixels tall and less than 100 kilobytes. Supplying exactly that avoids resampling on the way in, which is where cover photos usually lose their crispness. The minimum Facebook accepts is 400 pixels wide by 150 tall, and anything at that end gets stretched to fill the space and looks soft.
Desktop and Mobile Crop It Differently
Facebook's help page describes the two displays separately. On computers the cover photo "left aligns with a full bleed and a 16:9 aspect ratio"; on mobile devices it "left aligns with a full bleed and a 2.4:1 aspect ratio". Those are two different shapes, and neither is the 2.7:1 of the file you upload — which is why a cover that looks perfectly balanced in an image editor can arrive trimmed on both.
The word doing the work in both descriptions is "left". Because the image is anchored to the left edge rather than centred, the right-hand end of a wide cover is the first thing to disappear as the container narrows. If your design has a logo at one end and a strapline at the other, put the thing you cannot afford to lose on the left. Facebook also notes that on mobile the profile picture overlaps the cover photo by approximately 40 pixels, so the very bottom of the left-hand side is spoken for as well.
Why 100 KB Is the Number That Matters
100 KB is a tight budget for a photograph. An 851×315 image is 268,065 pixels, so 100 KB across it works out at roughly 0.38 bytes per pixel — achievable for a JPEG of a photo with smooth areas, awkward for one with foliage, crowds, or fine texture everywhere. If your cover will not fit, the fix is usually to simplify the image rather than to push JPEG quality lower, because it is exactly the busy detail that costs the bytes and exactly the busy detail nobody reads in a 315-pixel-tall strip.
The other word worth noticing in Facebook's recommendation is sRGB. If you export from a photo editor in Display P3 or Adobe RGB — increasingly the default on Apple hardware — saturated brand colours can shift when the file is converted for display. Converting to sRGB yourself, before upload, means you see the shift and can correct it, instead of discovering it on someone else's screen.
Before You Upload a Facebook Cover
- Keep the essential content left-of-centre and away from the top and bottom edges — the desktop container is 16:9 and the mobile one 2.4:1, so both ends and both edges are at risk.
- On desktop, your profile picture sits over the lower-left of the cover. Leave that area clear even though the left is otherwise the safest place to put things.
- Facebook names 100 KB as the fast-loading target. For text-heavy or flat-colour covers a PNG will often hit it while staying crisper than a JPEG.
- The minimum is 400×150. Anything smaller gets upscaled by Facebook and looks blurry.
- A Page cover and a personal profile cover are not interchangeable; this page follows Facebook's published Page cover guidance.
Nothing is uploaded — the resizing runs in your browser. How that works, and why it matters.
Dimensions verified: 2026-09-08 · source