Vertical video resolution: 9:16 sizes from 720p to 4K

Vertical video resolution is 1080×1920 pixels for 1080p, 720×1280 for 720p, and 2160×3840 for 4K: the standard 16:9 sizes turned on their side into a 9:16 frame. Any width works as long as the height is the width × 16 ÷ 9. Sume's Timeline renders 1080×1920 by default, and neither Timeline nor compose writes an edge over 2160 pixels, so a 4K vertical has to be enlarged after the edit.

The 16:9 sizes come from YouTube's Help page Video resolution & aspect ratios, and the Sume facts from the Timeline 1.0, Timeline compose, Video trim, Video generation, and Avatar videos docs and the Sume API reference, all read on 2026-09-28. The 9:16 sizes are our arithmetic.

What size is a vertical video in pixels?

Turn each 16:9 size upright and you have its 9:16 size. The quality label names the short edge, so 1080p vertical is 1080 pixels wide. 480×854 is 9:16 only to two decimals, because 854×480 is not an exact 16:9. The same sizes turned landscape are in what size is 16:9 in pixels, and what each platform asks for is compared in social media video sizes.

How do I work out a 9:16 size from any width?

Multiply the width by 16 and divide by 9: 1080 × 16 ÷ 9 = 1920. Going the other way, width = height × 9 ÷ 16. If your tool needs even edges, as Sume's Timeline does, pick a width that is a multiple of 18: the height is then a multiple of 32 and both come out even. 1080 = 18 × 60 gives 1920, and 1206 = 18 × 67 gives 2144.

What vertical sizes can Sume render?

It depends on the tool. The editing tools take pixel sizes; generation takes a shape and a quality tier.

• Timeline 1.0 renders and Timeline compose shots default to a 1080×1920 MP4. Timeline's output.width and height take even integers from 256 to 2160, compose caps each edge at 2160, and so does a trim's optional output resize.
• So the largest exact 9:16 frame they can render or resize to with even edges is 1206×2144, and 2160×3840 is out of their reach.
• Video generation (POST /v1/videos) takes aspect_ratio: "9:16" plus a resolution tier such as 720p or 1080p, and each model lists the tiers it accepts in supported_resolutions. Every v1 model refuses size with 400 unsupported_parameter, so you can't ask for exact pixels; vertical 9:16 video generation lists the ratios by model.
• Avatar videos default to aspect_ratio 9:16, and 720p is the documented resolution.

How do I get a 4K vertical video?

Upscale the finished 1080×1920 render. Sume Video Upscale 1.0 at scale_ratio: 2 takes it to about 2160×3840; the API reference doesn't state the exact output size. Do it last, because a Timeline render or a compose can't write 2160×3840 back out. How to upscale video to 4K covers the factors, the request, and the upscale's 30-second duration_seconds limit.