Facebook Post size: 1080 x 1350 pixels.

Facebook has no published organic feed size, so the reference point is its Ads Guide, which gives 1440 by 1800 pixels at 4:5 for feed images, a 600 pixel minimum width, JPG or PNG and a 30 MB cap. Organic posts follow the same display rules, and 1080 by 1350 is the same ratio at the width most people export, which means one file covers a Page post and the linked Instagram account without a re-crop.

A single image is shown at the column width and kept at its own ratio between 1.91:1 and 4:5. Taller uploads, such as a 9:16 phone photo, are trimmed toward 4:5 in the feed with the whole image a tap away. Multi-image posts are a different story: they go into a collage that crops each picture to a square or a 4:3 tile, so a graphic with type near the edge should be posted on its own.

Facebook compresses more aggressively than Instagram. Save JPG around quality 90, or PNG for flat colour and text, and keep body type above roughly 30 pixels tall. One more trap: pasting a link into the caption of a photo post keeps it a photo post, while posting the link first turns it into a link card at 1.91:1, which is a different placement entirely.