Cartesia vs Fish Audio: Which Voice AI Platform Should Builders Choose?

The Short Answer

Cartesia and Fish Audio are two of the most popular challengers to ElevenLabs for developers who need speech in their products. Both offer cheap entry plans, voice cloning and a usage-based API, but they optimize for different workloads. Cartesia is real-time voice infrastructure: Sonic 3.6 text-to-speech, Ink-2 speech-to-text and managed voice agents with per-minute pricing, built for live conversations. Fish Audio is high-volume speech generation: S2 and S1 models, generous creator allowances, many voice slots and a flat API price of about $1.25 per hour of speech.

Choose Cartesia when latency and conversation handling decide the product, such as phone agents, assistants and interactive characters. Choose Fish Audio when cost per hour, cloning many voices and long-form generation matter more, such as narration, audiobooks, video voiceovers and character libraries.

Prices and specifications come from Cartesia's and Fish Audio's official pricing pages and documentation, checked on October 1, 2026. Cartesia pricing, Cartesia TTS models, Fish Audio plans, Fish Audio API pricing.

Product Focus

Cartesia's text-to-speech model is Sonic 3.6, which it describes as its fastest and most natural model, speaking 44 languages. Ink-2 handles speech-to-text. Managed Agents run voice calls at $0.06 per minute, with telephony at $0.014 per minute on Cartesia-provided numbers, and LLM usage during calls is currently free for agents created in Cartesia's interface for a limited time. Every plan includes unlimited workspace seats, commercial use from Pro and instant voice cloning, with professional voice cloning from Startup.

Fish Audio's current models are S2.1 Pro, S2 Pro and S1, all priced the same in the API, with a free s2.1-pro-free model. The company also publishes open research models such as Fish Speech and OpenAudio. Its web app covers text-to-speech, cloning, a voice changer, Story Studio, audio translation, sound effects and Voice Design on paid plans, and its API supports streaming, speech-to-text and an MCP server.

Cartesia sells a complete real-time stack. Fish Audio sells low-cost, high-quality speech generation with a strong creator app.

Plans and Pricing

Fish Audio's annual prices include a limited-time 50% discount on yearly billing. Fish Audio estimates a minute of generation at roughly 600 to 625 credits. Cartesia's $5 Pro plan converts to about 133 minutes of text-to-speech and about 9 hours of speech-to-text, while its paid plans also include prepaid agent usage equal to the plan price.

API Costs Side by Side

The Cartesia hourly figure divides the $5 Pro plan by its roughly 133 minutes of speech; larger plans lower the effective rate. For pure narration volume, Fish Audio is cheaper per hour. For a live agent, Cartesia's bundled agent minutes and telephony usually make total cost easier to manage than assembling the pieces yourself.

Where Cartesia Wins

A complete real-time stack. Speech-to-text, text-to-speech and managed agents from one vendor, with telephony, reduce integration work for phone and app agents.

Developer-friendly entry. The $5 Pro plan includes a commercial license, instant cloning, about 133 minutes of speech, about 9 hours of transcription and $5 of agent usage.

Unlimited seats. Whole engineering and product teams can share one workspace at no extra cost.

Enterprise compliance. DPAs and BAAs, SSO and security questionnaires are available for regulated industries.

Where Fish Audio Wins

Cost per hour. At about $1.25 per hour through the API, Fish Audio is one of the cheapest ways to generate natural speech at volume.

Generous creator plans. About 200 minutes for $15 a month on Plus and about 1,620 minutes on Pro make Fish Audio attractive for YouTubers, audiobook producers and podcasters.

Many cloned voices. Professional voice slots on every paid plan, plus unlimited public and 10 private voice slots on Plus, suit projects with large casts of characters.

Open research and deployment options. Open models such as Fish Speech and OpenAudio, plus enterprise zero data retention and on-premise deployment, appeal to teams with strict data requirements.

Voice Cloning and Voice Libraries

Both platforms clone voices from samples, with different packaging. Cartesia includes instant voice cloning from the $5 Pro plan and professional voice cloning from the $49 Startup plan, and localizing a cloned voice into another accent costs 225 credits per added accent. Fish Audio sells cloning through voice slots: Plus includes unlimited public and 10 private voice slots plus one professional voice slot, Pro five professional slots and Max 15. Fish Audio's FAQ says premium subscribers can use verified voices they own commercially, while free-plan output is for personal, non-commercial use. On either platform, clone only voices you have permission to use and keep consent records.

Latency and Streaming

Real-time products need the first audio to arrive quickly and to keep streaming smoothly. Cartesia's product line is designed around streaming text-to-speech and turn-aware speech-to-text for agents, and Sonic 3.6 is the model it recommends for speed. Fish Audio supports streaming through its API as well, and its concurrency rises from 5 to 15 and then 50 requests as your cumulative spending grows past $100 and $1,000. Published latency figures are measured in each vendor's conditions, so test from the region where your servers run.

Common Mistakes When Comparing

The first mistake is comparing the two vendors' credits. Cartesia credits and Fish Audio credits buy different amounts of speech, so convert both to minutes for your scripts. The second is ignoring speech-to-text: for agents, transcription accuracy and turn detection matter as much as the voice. The third is underestimating concurrency. A product with many simultaneous users needs enough parallel requests, so check plan limits early and plan for the tier you will need at launch, not the one you need for testing.

Budget Examples

An audiobook startup generating 200 hours of narration a month. Through Fish Audio's API, 200 hours costs about 200 × $1.25 = $250 a month. On Cartesia, 200 hours is 12,000 minutes of speech; at the Pro plan's ratio of about 133 minutes per $5 that would be roughly $450, and Cartesia's larger plans and volume pricing would lower it. Fish Audio is the cheaper route for this workload.

A scheduling assistant handling 3,000 calls a month of three minutes each. That is 9,000 agent minutes. On Cartesia's managed agents, 9,000 × $0.06 = $540, plus $126 of telephony on Cartesia numbers. The Startup plan's $49 includes $49 of agent usage, and Scale's $299 includes $299. Building the same agent on Fish Audio means combining its streaming text-to-speech and $0.36-per-hour speech-to-text with your own agent framework and telephony provider, which can cost less but takes more engineering.

Decision Framework

How to Evaluate

For a real-time product, build the same short conversational flow with both: a greeting, a question, an interruption and a confirmation. Measure time to first audio from your own servers, transcription accuracy on names and numbers, and how naturally each voice handles short replies. For a narration product, generate the same 10-minute script with both and compare naturalness, pronunciation and cost.

Many teams end up using both: Cartesia for live agents where latency rules, and Fish Audio for batch narration and character libraries where cost per hour rules. Recheck pricing before committing, as Fish Audio's 50% annual discount is a limited-time offer.

Before committing, confirm three terms with whichever vendor you choose: how overages are billed when you exceed your plan, how concurrency limits rise as you grow, and what happens to cloned voices and stored audio if you cancel. Run a two-week pilot with real traffic, record cost per minute and failure rates, and use those numbers rather than headline prices to make the final call. Both vendors ship new models often, so repeat the test when a major version is released.

If your product needs both live conversation and bulk narration, there is no need to force one vendor to do both. Route each workload to the tool that is cheaper or faster for it, and keep the integration behind a simple internal interface so you can switch later.

Both companies publish their pricing and model documentation openly, which makes this kind of side-by-side test straightforward to repeat.