Instagram's 1% aspect tolerance: which odd sizes still pass 9:16

Instagram's Stories and Feed video ad pages list an aspect ratio tolerance of 1%, so a frame a hair off 9:16 can still count. The safest answer is to render exactly 9:16, which Sume Timeline does at its default of 1080 x 1920.

This post turns the 1% figure into concrete pixel heights for a 1080-wide frame. The tolerance figure is quoted from the Instagram pages (read 2026-10-10). How Instagram measures the tolerance is not spelled out there, so the arithmetic below assumes it is relative to the ratio, which is my reading, not Instagram's wording.

What the pages state

Both the Stories page and the Feed page list the ratio as 9:16 and the aspect ratio tolerance as 1%. The Stories page lists 1440 x 2560 pixels, and the Feed page lists 1080 x 1920 pixels. Both list a 4 GB maximum and a minimum width of 250 pixels. Neither page defines the tolerance beyond the percentage.

That vagueness is a reason not to lean on it. A tolerance is a margin for rounding, not a licence to ship a 1080 x 1900 frame because it looked close.

The arithmetic for a 1080-pixel width

A true 9:16 frame has a width-to-height ratio of 0.5625. Taking 1% of that as the allowed spread gives 0.5569 to 0.5681. For a 1080-pixel width, the matching heights run from 1080 divided by 0.5681, about 1,901, to 1080 divided by 0.5569, about 1,939. The table lists some sizes against that window.

Rendering exactly 9:16 in Sume

Timeline 1.0 returns a 1080 x 1920 MP4 by default. If you set output.width and output.height yourself, they must be even integers from 256 to 2160, so 1080 x 1920 and 720 x 1280 are both valid. Each video slot has a fit mode: cover fills the frame and crops the overflow, contain letterboxes, stretch distorts, and blur fills the bars with a blurred copy. Cover is the one that gives you an exact frame without bars.

If the source is 16:9 and you want a deliberate crop rather than centre cover, the video filter crop op takes fractions of the source frame. The compiler rounds to even values for yuv420p, which is why crop fractions rarely land on a perfect ratio by themselves; render through Timeline afterwards if the exact ratio matters.

A short preflight

Use the unbilled Timeline plan call to confirm the duration, and read the output size in your own code before uploading. Do not trust a file name. If a clip comes from elsewhere and is not 9:16, import it and render it through Timeline with cover rather than hoping the tolerance saves it.

• Aim for exactly 1080 x 1920 or 720 x 1280.
• Treat the 1% figure as rounding margin only.
• Keep text inside the safe zone the pages describe: about 14% top, 35% bottom, 6% sides.

Why the two pages disagree on size, and what to do

The Stories page asks for 1440 x 2560 while the Feed page asks for 1080 x 1920, yet both name the same 9:16 ratio and the same 1% tolerance. That is a useful reminder that ratio and resolution are separate checks. A clip can pass the ratio test and still be smaller than the resolution a placement lists. Read the page for the placement you are buying, not the neighbouring one.

For Sume users the practical consequence is a ceiling. Timeline output edges stop at 2160, and 1440 x 2560 would need a 2560 edge, so that exact size is not something Timeline can output. A 1080 x 1920 render covers the Feed listing exactly. For the Stories listing, say plainly in your own notes that the Sume render is smaller than the page's stated resolution, and decide whether that placement tolerates it before you commit budget.