Runway vs Seedance for Video Ads: Pay 2.5x per Second for 3x Longer Takes

One 30-second take, or three 10-second clips

A growth lead at a supplement brand has a 30-second Reels script and one Runway account. She has two engines to spend it on.

The first is Runway's own Gen-4.5. On Runway's developer API it caps a clip at 10 seconds, so her script becomes three clips joined in the edit: 360 credits, or $3.60 at the API's rate of a cent a credit. The second is ByteDance's Seedance 2.5, which Runway also sells. It renders all 30 seconds in one generation for 900 credits, or $9.00.

That is the matchup in two lines. Seedance 2.5 costs 2.5 times as much per second at 720p. It also runs three times as long per take.

"Runway vs Seedance" sounds like two rivals. It is closer to one store selling two engines for the same credits. Runway's Seedance 2.5 page says "Seedance 2.5 is available on all paid plans," and the Pro and Max cards on its pricing page list Seedance 2.5 among their models. So the useful question is not which company to pick. It is which engine should get the credits for which shot.

One disclosure before the numbers: Novoads competes in AI video ads and offers Seedance 2.5 too, so we have a stake in half of this comparison. Every rival price below is the vendor's own, as of September 2026.

The short answer for ad work

Neither engine wins every shot. Gen-4.5 is the cheaper second of video. Seedance 2.5 is the longer take, with sound and a deep reference budget in one pass.

Choose Gen-4.5 when

• The shot is short and visual: a pour, a fabric drop, a product turning on a plinth. Runway sells Gen-4.5 on physics.
• You are testing many openings, and the cost per second decides how many you can afford.
• The ad is headed for a professional edit. Runway's API offers ProRes, PNG sequence and HDR output on Gen-4.5.

Choose Seedance 2.5 when

• The script runs past 10 seconds and a cut in the middle would hurt it, like a spoken testimonial or a one-take demo.
• You want sound back with the picture. Runway's Seedance page says "your video comes back with visuals and sound."
• The brief leans on references: product shots, a style frame, a voiceover or an earlier ad. Runway's API accepts up to 30 images, 10 videos and 10 audio clips for it.

Edge for short visual shots and cheap hook tests: Gen-4.5. Edge for long takes with sound and heavy references: Seedance 2.5.

Runway sells both engines, which changes the question

The two engines reached Runway by different roads, and that explains most of the price gap.

Gen-4.5 is Runway's own model

Runway announced Gen-4.5 on December 1, 2025, and says "Gen-4.5 is available across all paid Runway plans." Its API changelog reads "February 10th, 2026 - Gen-4.5 is now available on Runway Dev," with durations of 2 to 10 seconds. The API takes text or an image as input and returns video.

It is also the engine Runway builds delivery around. On the API, professional formats such as ProRes and PNG sequences are "Available on Gen-4.5 and Aleph 2.0," with true HDR on Gen-4.5 alone. For an agency cutting in a grading suite, that matters more than a few cents a second.

Seedance 2.5 is ByteDance's model, on Runway since August

ByteDance launched Seedance 2.5 in a post dated July 31, 2026, saying it "extends single-pass video generation from 15 to 30 seconds." Runway's developer platform followed a week later: "August 7th, 2026 - Seedance 2.5 ( seedance2_5 ) is now available on Runway Dev," at 480p or 720p, with 1080p added on August 15. The API takes text, images or video as input.

Runway markets it straight at marketers. Its Seedance page promises "Up to 30 seconds in one generation" and output "at 480p, 720p and 1080p," and tells ad teams: "Go from idea to a finished ad without a shoot to book." Our explainer on Seedance 2.5 covers what the model itself does beyond Runway.

Runway's shelf holds more than these two

Runway describes its lineup as "Runway models like Gen-4.5 and Aleph 2.0, plus third-party models like Nano Banana Pro 2, GPT Image 2, Kling 3.0, Kling O3, Veo 3.1, Seedance 2.5 and more." So one subscription reaches several other video engines too. Our Runway vs Kling comparison prices Kling 3.0 on the same shelf, our Runway vs Veo comparison does the same for Veo 3.1, and ByteDance's model runs outside Runway too:

• ByteDance's own apps. The July 31 launch post said Seedance 2.5 was "rolling out on Jimeng AI, Doubao Pro, and other platforms."
• API hosts such as fal, which bill Seedance 2.5 by resolution and length.
• Ad tools that wrap the model in a script-to-ad workflow, which is what Novoads does.

Cost per second on Runway's meter

Runway prices both engines in credits, so they compare cleanly. The API sells those credits at a flat rate; the web plans bundle them monthly at a different effective price.

The list rates at a cent a credit

Runway's API pricing page says "Credits can be purchased for $0.01 per credit in the developer portal for an organization." At that rate:

Engine on Runway's API	Credits per output second	Per second
Gen-4.5	12	$0.12
Seedance 2.5, 480p	20	$0.20
Seedance 2.5, 720p	30	$0.30
Seedance 2.5, 1080p	68	$0.68
Seedance 2.0, 480p or 720p	36	$0.36
Seedance 2.0 Mini, 480p or 720p	16	$0.16

Two things stand out. At 720p, Seedance 2.5 costs 2.5 times Gen-4.5 per second. And on this list it is cheaper per second than Seedance 2.0 at the same resolution. Runway Academy's credits page gives the same figures, 30 credits a second for Seedance 2.5 at 720p and 12 for Gen-4.5.

Surcharges and minimums that move the total

The headline rates leave out details that change an ad budget:

1. Reference video costs extra on Seedance 2.5. At 720p, Runway adds 15 credits per second of input and reference video, with combined video capped at 30 seconds. Reference images and audio are free. Add a 10-second clip of your current best ad as a reference to a 15-second take, and the take goes from 450 credits to 600.
2. Each Seedance 2.5 generation has an 80-credit minimum. It does not change the bill for an ad-length clip: the shortest duration the API launched with, 4 seconds, already costs 80 credits at 480p and 120 at 720p.
3. An "auto" duration is billed at the maximum up front. Runway's API reference says auto "is billed at the variant maximum up front; unused credits are refunded after the generation finishes." Set an explicit length when a batch has to fit a budget.
4. Gen-4.5's delivery formats cost extra. ProRes and PNG sequences add 5 credits a second; 10-bit and HDR profiles add 20.

What plan credits buy in Seedance 2.5

On Runway's web plans the math shifts, and our Luma AI vs Runway comparison counts each plan in Gen-4.5 clips. Standard is $15 a month for 625 credits, which Runway equates to 52 seconds of Gen-4.5, or about $0.29 a second. At the Academy's 30-credit rate, Seedance 2.5 at 720p works out to about $0.72 a second on Standard, and a single 30-second take is 900 credits, more than the plan's whole month.

Pro ($35 a month for 2,250 credits) and Max ($95 a month for 9,500) buy more room, and Max's card puts a "26% off" badge on its Seedance 2.5 chip, with the tooltip "26% off on 1080p generations." Extra credits come in a minimum purchase of 1,000.

Seedance 2.5 priced off Runway

fal sells the same model by the generation. For image-to-video it says "for 720p, you will be charged roughly $0.4730 per second of generated video," and its own worked example puts a 30-second 720p clip at about $13.87. fal counts frame area, so a vertical 720 by 1280 clip bills the same pixels as its 1280 by 720 example, and it notes that "wider aspect ratios have larger frame areas and cost more per second." fal does not bill input images, and Runway's Seedance 2.5 rate treats reference images as free. On list prices, Runway's API is the cheaper place to buy a second of Seedance 2.5 at 720p. Our guide to AI video credits shows how to turn any vendor's credit table into a cost per finished ad.

Clip length and the cost of a join

Per-second prices only compare fairly when the clips do the same job. Length is where they stop doing the same job.

Gen-4.5 stops at 10 seconds a clip

On Runway's API, a Gen-4.5 duration "Must be an integer from 2 to 10." A 15-second ad is two clips; a 30-second spot is three. That is plenty for a hook, a product close-up or a B-roll insert. It is not one continuous take of a presenter talking through a whole script.

Seedance 2.5 runs to 30 seconds, then extends

Runway's Seedance page calls it "Native 30-second output, with high-quality extension for longer clips," and adds "Room for a full ad or scene, not just a snippet." The API exposes that through a video-to-video extend mode, and ByteDance says the model "supports multiple rounds of extension."

Inside one take, Runway says "Multiple scenes, camera angles and pacing shifts come out of one generation, with no separate clips to stitch together." Sound comes along too: the API changelog describes Seedance 2.5 video "with optional generated audio." How to write one prompt that directs all 30 seconds, dialogue included, is the subject of our Seedance 2.5 prompt guide.

Why a join costs more than it looks

Three short clips are cheap to render and expensive to hide. Every join is a place where:

• the presenter's face, hair or light can shift between clips,
• the product can change angle, size or label position,
• a spoken line has to cross a cut without a jump in the voice,
• an editor spends time making the seam invisible.

For a 6-second hook, none of that matters. For a 30-second testimonial it is most of the risk, and it is the risk the extra 18 cents a second buys down.

Motion: two different pitches, no shared scoreboard

Both vendors make strong motion claims. Read closely, they are claims about different things.

Runway sells Gen-4.5 on physical accuracy

Runway's announcement says "Objects move with realistic weight, momentum and force. Liquids flow with proper dynamics," and that "fine details like hair strands and material weave remain coherent across motion and time." For an ad, that is the serum drop, the dress hem, the sneaker landing on concrete.

Runway also names its limits. One is object permanence: "objects may disappear or appear unexpectedly across frames (e.g., a cup vanishing after being occluded)." In a product ad, that is the bottle that vanishes when a hand passes in front of it.

ByteDance sells Seedance 2.5 on direction across a take

ByteDance's launch post says Seedance 2.5 "delivers notable gains in image, audio, and motion quality," and that "Within 30 seconds, the model can organize multiple logically connected shots." It also strengthens references "including clay render, motion, and creative references," so a rough 3D blocking pass or a reference clip can steer the camera path.

That is a different bet. It is less about one perfect pour and more about keeping a whole sequence coherent: the same face, the same pack, the same room, through several camera changes. These are ByteDance's own claims, so treat them as a brief for your test rather than a result.

The 1,247 Elo chart predates Seedance 2.5

Runway says Gen-4.5 "ranked #1 on the Artificial Analysis Text-to-Video benchmark with 1,247 Elo points," on a leaderboard dated November 30, 2025, where "Rankings are determined by blind human preference voting across thousands of pairwise comparisons." That snapshot came eight months before ByteDance launched Seedance 2.5, so it says nothing about this matchup. Realism is also a property of engines that many ad tools rent, which is why it rarely decides a purchase; we make that case in where AI UGC realism actually comes from.

Five motion tests before you commit a batch

Render the same brief on both engines and check each take for:

1. A liquid. A drop, a pour or a spray, the shot Runway pitches Gen-4.5 on.
2. An occlusion. A hand passes in front of the product. Watch for the vanishing object Runway names as a limit.
3. An orbit. The camera circles the pack. Does the label keep its shape and lettering?
4. A cut inside the take. Ask Seedance 2.5 for two angles in one generation. Is the product identical after the cut?
5. A long spoken stretch. Twenty seconds of a presenter talking. Is the mouth still with the voice at the end?

Keep the take that passes, not the engine that won last quarter. Once the survivors run, our guide to ad creative testing covers how to read a winner without fooling yourself.

Worked example: one 30-second spot and ten hooks

A supplement brand needs one 30-second vertical spot at 720p and ten 5-second alternate openings to test in front of it. The product photo goes in as the image input, the still-to-clip handoff our Seedance vs Nano Banana comparison covers. Here is the bill on Runway's API before retries.

All Seedance 2.5

• Spot: 30 seconds × 30 credits = 900 credits ($9.00), one take, sound on by default.
• Hooks: 10 × 5 seconds × 30 credits = 1,500 credits ($15.00).
• Total: 2,400 credits, or $24.00.

All Gen-4.5

• Spot: three 10-second clips, 30 seconds × 12 credits = 360 credits ($3.60), with two joins to hide.
• Hooks: 10 × 5 seconds × 12 credits = 600 credits ($6.00).
• Total: 960 credits, or $9.60.

The split

• Hooks on Gen-4.5: 600 credits ($6.00).
• Spot on Seedance 2.5: 900 credits ($9.00).
• Total: 1,500 credits, or $15.00. Add a 10-second reference clip of your best ad to the spot and it rises by 150 credits, to $16.50.

Two comparisons put those numbers in context. The all-Seedance brief on fal comes to about $13.87 for the spot plus ten 5-second clips at about $2.31 each, roughly $37 in total. On a Runway web plan, 2,400 credits at the Academy rate is more than Pro's 2,250 monthly credits.

The split rule: cheap seconds where a clip is short, the long take where a cut would show. It costs $5.40 more than all Gen-4.5 and saves the two joins on the one asset that has to hold attention for 30 seconds.

Where to run each engine

Seedance 2.5 runs in several places, so the last choice is the door you buy it through, the question our Higgsfield vs Seedance comparison asks of Higgsfield and fal.

Runway, when you want both on one balance

Runway is the simplest place to run the split: Gen-4.5 for short shots, Seedance 2.5 for the long take, one credit pool, and Gen-4.5's ProRes and HDR output when the ad goes to an editor. If the subscription is the sticking point, our Runway alternatives roundup compares six other tools for ad work.

An API host, when you only need raw Seedance seconds

For a developer building a pipeline, per-second list prices matter most. Runway's API rate for Seedance 2.5 at 720p sits below fal's, while fal publishes a token formula that makes odd aspect ratios easy to price in advance. Both skip the plan-sizing question entirely.

Another engine on the shelf, when Seedance is not the fit

If the ad is a short spoken scene, Kling 3.0 sits on the same Runway shelf and is worth a test render. Our Kling vs Seedance comparison sets those two against each other on audio, length and control.

How Novoads solves the long take without an API account

Novoads is a global AI UGC video-ad generator: upload a product photo, write or auto-generate a script, pick an AI actor and export a vertical ad. Seedance 2.5 runs inside Novoads next to Seedance 2.0, Seedance 2.0 Mini, Kling v3 Pro, Google Veo 3.1 and Omni Flash, so the Seedance half of this comparison works without an API key or a Runway plan.

Seedance 2.5 priced in credits

In Novoads, Seedance 2.5 renders 4 to 30 seconds at 480p or 720p, in 9:16, 16:9, 1:1 and three other ratios, with sound on by default. At 720p:

• 5 seconds: 7.6 credits.
• 15 seconds: 19.6 credits.
• 30 seconds: 37.6 credits.

480p costs half. Novoads starts at $49/month (Starter, 50 credits per month), and all plans are published on /pricing. The worked example's spot and ten 5-second hooks come to 113.6 credits on Seedance 2.5, which fits the $99 Studio Light plan's 150 monthly credits, and that is more per second than Runway's API list price. A cheaper route tests the hooks on Seedance 2.0 Mini at 1.5 credits for 5 seconds and spends the long take on 2.5: 52.6 credits for the whole brief, just over Starter's month. What the credits buy around the clip is the rest of the ad in one project: scripts, AI actors, voices in 31 languages and captions.

What Novoads does not do

Novoads does not offer Runway's Gen-4.5, so the cheap short shot and the ProRes or HDR delivery stay with Runway. It runs Seedance 2.5 at 480p and 720p, while Runway sells it at 1080p too, and it caps references at 9 images, 3 videos and 3 audio clips, against 30, 10 and 10 on Runway's API. If a brief needs 1080p or a large reference board, Runway is the better door. If it needs a steady run of product-first vertical ads with a script and an actor, you can start on Novoads.

Price the take, not the second

On Runway's current price list, a second of Gen-4.5 is cheaper than a second of Seedance 2.5, and nothing in this comparison changes that. But an ad is bought as a finished take, not as a pile of seconds. Put the short visual shots on Gen-4.5, give the take that cannot survive a cut to Seedance 2.5, and let the joins you never had to hide pay for the difference.