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1080x1350 Aspect Ratio Explained: The 4:5 Instagram Portrait Size (2026)

1080 1350 Ratio: What 1080x1350 Means and Why Instagram Uses It A 1080 x 1350 pixel image has an aspect ratio of 4:5, which is a decimal ratio of 0.800 — the tallest portrait size Instagram displays in the feed without cropping. You get 4:5 by dividing both numbers by their greatest common divisor of 270: 1080 ÷ 270 = 4 and 1350 ÷ 270 = 5. Drop any width and height into our Aspect Ratio Calculator(/tools/aspect-ratio-calculator) to confirm the simplified ratio and decimal in one click. A common point of confusion is people typing "1080 1350" and expecting it to mean some exotic ratio. It does not. It is plain 4:5 — the same 4:5 you would write for an 8x10 photo print scaled up. The mistake to watch for: if you resize a 1080x1350 graphic to 1080x1080 for a square post, you lose 270 pixels of height, which...