Seedance output size in pixels: what 720p 9:16 or 1080p 21:9 means

On Sume, Seedance sizes come from the resolution and aspect ratio together: 720p 16:9 is 1280x720, 720p 9:16 is 720x1280, 1080p 16:9 is 1920x1080 and 1080p 21:9 is 2205x945. These are the dimensions the price estimate uses, from the repo pricing tables read 2026-10-05; the API does not accept a size field and returns 400 unsupported_parameter if you send one (Video generation).

What are the sizes?

480p is not 480 pixels on a side: it is a 496-pixel or 864-pixel edge for 9:16, and a narrower box for 21:9. The table lists four common ratios; 4:3 and 3:4 are in the catalog too.

Why does the size matter for price?

Seedance is billed on video tokens: width x height x seconds x 24 fps / 1024. A wider box has more pixels, so more tokens. At 720p, 21:9 is 1470x630 = 926,100 pixels against 921,600 for 16:9, so they cost almost the same; see Seedance 2.5 aspect ratio price.

How do I request a size?

Send resolution and aspect_ratio, not size.

curl -X POST https://api.sume.com/v1/videos \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"seedance-2.5","prompt":"A lighthouse at dusk, waves","duration":4,"resolution":"1080p","aspect_ratio":"21:9"}'

Does the file I download have exactly those pixels?

Inspect the downloaded MP4 with the video inspect tool if the exact output size matters for an ad spec, rather than assuming the table.