Crop 1920x1080 to 9:16 around a left-third subject: x = 0.1751

To keep a subject standing on the left third of a 1920x1080 frame, send a crop op with x 0.1751, y 0, width 0.3164 and height 1. The strip is about 607 pixels wide and the full 1080 tall, centered on pixel 640, the middle of the left third. Video filter costs $0.02 per encode job and its check is free (as of 2026-10-08). The centered version of this crop, with x 0.3418, is a different post's answer; here the subject is not in the middle.

The arithmetic

A 9:16 strip from a frame that is 1080 pixels tall is 1080 x 9 / 16 = 607.5 pixels wide. As a fraction of the 1920-pixel width, that is 607.5 / 1920 = 0.3164. To center the strip on pixel 640 (one third of 1920), its left edge goes 303.75 pixels to the left of 640, at pixel 336.25, so x = 336.25 / 1920 = 0.1751. The right edge is 0.1751 + 0.3164 = 0.4915 of the width, comfortably inside the frame.

The docs rule is that x and y are in 0 to 1, that width and height are in 0.05 to 1, and that x + width and y + height cannot pass 1. Our numbers satisfy all of them. The compiler rounds to even values for yuv420p, so the real output is roughly 606 x 1080.

Does it clear TikTok's size line

TikTok's page gives 540x960 as the minimum for 9:16 non-Spark ads. A 606 x 1080 strip is above both numbers. But 606 / 1080 is 0.5611 and 9 / 16 is 0.5625, so the strip is very close to, and not exactly, 9:16. Whether the platform rounds that is not stated on the page. To remove doubt, run the strip through Timeline with the output set to 540 x 960 (or 1080 x 1920) and fit cover; the render makes the frame exact.

• Filter encode: $0.02 per job; check: $0.00
• Timeline render of a 30-second clip: ceil(30 / 60) = 1 minute x $0.10 = $0.10
• Total for crop plus exact-size render: $0.12

Limits to remember

The source for Video filter is capped at 300 seconds, so a 5-minute landscape clip fits and a 6-minute one has to be trimmed first (Video trim, $0.02, source up to 1800 seconds). A crop is a fixed rectangle: if the subject walks to the right of the frame, the strip loses them. For a moving subject, cut the clip at the move and use a different x in each piece, then join them in Timeline.

A crop does not resize. The filter keeps the source frame rate and audio, and it returns a new MP4 while the source stays unchanged. Run the check first with the same body, read the compiled filters list to confirm the crop is there, then send the encode with an Idempotency-Key.