Instagram's post formats, side by side
| Format | Ratio | Export size | Decimal | Notes |
|---|---|---|---|---|
| Portrait (feed) | 4:5 | 1080×1350 | 0.8 | The tall feed format photographers export; 25% more height than 1:1 |
| Square | 1:1 | 1080×1080 | 1 | The classic; still fine everywhere |
| Landscape (feed) | ≈1.91:1 | 1080×566 | 1.9081 | The usual landscape export; "1.91:1" is itself a rounded label |
| Reels / Stories | 9:16 | 1080×1920 | 0.5625 | Full-screen vertical, a separate surface from the feed |
The 4:5 portrait format exists because the feed caps how tall a post may appear: taller uploads get cropped or shrunk to fit. 4:5 has long been the tallest ratio Instagram recommends for feed photos, which is why it became the default for photographers who want maximum feed presence. Feed layouts and crop rules do get redesigned, so confirm in the app's own preview before publishing — the part that does not change is the arithmetic below.
Worked example: phone photo → 4:5
A 12 MP phone photo in portrait is 3024×4032, ratio 3:4 (decimal 0.75). Cropping to 4:5 (0.8) keeps the full 3024 width and needs a height of 3024 × 5 ÷ 4 = 3780 — so you trim 4032 − 3780 = 252 px, exactly 6.25% of the height, split between top and bottom in a center crop. This is the calculator's default setup on this page; the "Crop" preview dims precisely that band. Export at 1080×1350 afterwards and nothing further is lost — 3024×3780 and 1080×1350 are both exactly 4:5.
Worked example: landscape camera shot → 4:5
A 24 MP camera file is 6000×4000, ratio 3:2 (decimal 1.5) — landscape. Turning it into a 4:5 portrait keeps the full 4000 height and a width of only 4000 × 4 ÷ 5 = 3200 px. That discards 6000 − 3200 = 2800 px, 46.7% of the image width. There is no rounding trick to soften that; it is the geometric distance between 1.5 and 0.8. If the subject is not centered, crop manually rather than letting an app center-crop half your photo away.
Why 4:5 beats 1:1 for feed presence
At the delivery width of 1080 px, a square post renders 1080 px tall and a 4:5 post renders 1350 px tall — 25% more pixels of screen height for the same upload effort. That arithmetic, not aesthetics, is why 4:5 quietly replaced the square as the photographer's default. The full-screen surfaces (Reels, Stories) use 9:16 instead — a different trade-off covered on the 9:16 vertical video page.
Related pages
Check what ratio any file actually is with the pixels-to-ratio lookup, run any custom ratio on the main calculator, or see the horizontal standard on the 16:9 resolution chart.