Synthesia's 500 signup credits: 5 minutes of video or 1 survey reply

Five hundred credits buy roughly five minutes of Synthesia video, six minutes of dubbing with lip-sync, or one survey response, if you use the per-minute credit costs on Synthesia's October 1 plans page. The page lists about 100 credits a minute for video, 80 a minute for dubbing with lip-sync, and 350 credits for each survey response. The same 500 credits also come with separate allowances, so the practical question is which one you spend them on first.

The arithmetic

Credit costs are from Synthesia's help page. The page says all plans receive 10 minutes of video, 3 survey responses, 500 credits and 60 minutes of Interactive Avatar once at signup, and that Creator was renamed Pro with 6,000 credits. I did the division below; Synthesia does not state these totals.

Setting that beside Sume

Sume prices by the second in dollars, so there is no credit conversion to do. For lip sync, the H3 Max route bills ceil(duration_seconds) at $0.0625 (480p), $0.10 (768p) or $0.20 (1080p) per second, from the fal list prices times a 1.25 margin. Six minutes of lip-sync output at 768p is 360 seconds, or $36.00. I am not putting a dollar value on 500 Synthesia credits, because the page I read does not give a dollar price for them on every plan.

How far the free tier goes

Because the allowances are listed separately, a new account can try several things without choosing. The 60 minutes of Interactive Avatar are for live sessions, the 10 minutes of video are for rendered clips, and the 500 credits are the flexible part. A sensible order is to render one real script, test one dubbing minute if you translate, and keep the rest. Survey responses at 350 credits each are the most expensive item per use, so check whether the three free responses already cover your trial before you spend credits on them.

The same discipline works on Sume, where a funded balance is spent per job and each create call shows a reserve. Run the smallest job that answers your question first: a 5-second lip-sync clip at 480p reserves ceil(5) x $0.0625, which is $0.3125.

A fair test for the free allowance

Spend the free credits where they tell you the most about fit.

• Take one real 60-second script from your own work, not a demo line.
• Render it once as video in Synthesia (about 100 credits) and once on Sume as an Avatar 1.0 talking video.
• Compare script handling, voice, and the way each tool handles a mistake: Sume refuses an over-long script before rendering, and refunds a failed job.
• Note the time to first usable file, not just the price.
• Decide on the output, then do the price math with your real volume.

What Sume does not do

Sume does not offer a signup credit pool that I could find in the docs I read, and it has no survey-response product. The closest thing is a recorded question clip played to a viewer, which does not collect answers. If collecting answers matters, that is a real gap against the Synthesia feature.