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AI · head to head

Cartesia vs Sonix

Cartesia logo

Cartesia

AI

Real-time voice AI platform for speech generation, transcription, and voice agents

From
Free
Rated
-
Full reviewWebsite
Sonix logo

Sonix

Translation

Automated transcription and translation with per-hour pricing published up front

From
$10/month
Rated
-
Full reviewWebsite

The short version

  • Only Cartesia has a free tier, so it costs nothing to try first.
  • Each has a real cost: Cartesia instant and professional voice cloning are gated behind paid Pro and Startup tiers, unavailable on the free plan.; Sonix monthly hour allowances are small relative to the subscription price: the $25 Core plan includes five hours, which at the published $10 overage rate means the subscription is only worth buying for storage and features rather than for the hours.
  • They diverge on capability: Cartesia covers Sonic text-to-speech, Sonix covers Automated transcription.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Cartesia and Sonix actually diverge.

Attributes where Cartesia and Sonix differ
AttributeCartesiaSonix
Starting priceFree$10/month
Pricing modelfreemiumPer hour of transcription
Free tierYesNo
CategoryAITranslation

Identical on both: platforms (web, api), user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Cartesia

  • Sonic text-to-speech
  • Ink speech-to-text
  • Line voice agent platform
  • Instant and professional voice cloning
  • Flexible deployment
  • Telephony integration

Only in Sonix

  • Automated transcription
  • Translation
  • Synchronised editor
  • Subtitle export
  • Custom dictionary
  • Search across media
  • Pay-as-you-go option
  • Enterprise compliance

What people use each for

The jobs each tool is most often brought in to do.

Cartesia

  • Building low-latency voice agents for customer supportnot Sonix
  • Real-time transcription for conversational applicationsnot Sonix
  • Voice cloning for branded synthetic voicesnot Sonix
  • On-device or on-premise voice AI for regulated industriesnot Sonix

Sonix

  • A journalist transcribing interviews in several languages who needs the transcript searchable and quotable within minutes rather than accurate to a contractnot Cartesia
  • A qualitative research team coding focus group transcripts, where speaker separation and an editable transcript matter more than a certified accuracy figurenot Cartesia
  • A podcast producer generating subtitle files and show notes from each episode without adding a human transcription suppliernot Cartesia
  • A small documentary team subtitling foreign-language footage where transcription and translation in one tool avoids a second vendornot Cartesia

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Cartesia

  • Instant and professional voice cloning are gated behind paid Pro and Startup tiers, unavailable on the free plan.
  • Voice agent calls carry a separate per-minute usage fee ($0.06/minute) on top of subscription credits.
  • Enterprise features like SSO and BAAs require a custom sales conversation rather than self-serve upgrade.
  • Free tier concurrency limits (2 TTS, 8 STT concurrent requests) may be restrictive for testing production-like load.

Sonix

  • Monthly hour allowances are small relative to the subscription price: the $25 Core plan includes five hours, which at the published $10 overage rate means the subscription is only worth buying for storage and features rather than for the hours.
  • Unused hours do not accumulate into a meaningful reserve, so an irregular workload of a heavy month followed by a quiet one pays overage in the first and wastes allowance in the second.
  • There is no human correction tier at self-service prices, so anyone with an accessibility or legal accuracy obligation has to add a separate supplier or a member of staff to the workflow.
  • The cited 99 percent accuracy is a best-case figure on clean single-speaker audio, and overlapping speakers, strong accents, technical vocabulary and room noise degrade it enough that editing time, not transcription cost, becomes the real expense.
  • Storage is capped per plan at 25GB to 100GB, and video files consume it fast, so long-running teams end up deleting source media or upgrading a tier for storage they do not otherwise need.

Pricing, plan by plan

Cartesia

Free
  • FreeFree
    • 20,000 credits/month
    • TTS and STT included
    • 2 concurrent TTS requests, 8 concurrent STT requests
  • Pro$4/month
    • 100,000 credits/month
    • Commercial use license
    • Instant voice cloning
  • Startup$39/month
    • 1.25M credits/month
    • Professional voice cloning
    • Organizations support
  • Scale$239/month
    • 8M credits/month
    • Priority support
    • High concurrency limits

Sonix

$10/month
  • Pay As You Go$10/month
    • $10 per hour transcribed
    • No subscription
    • 30 minutes free to trial without a card
  • Core$25/month
    • 5 hours a month of transcription and translation
    • 25GB storage
    • $275 a year if billed annually
  • Advanced$50/month
    • 20 hours a month
    • 50GB storage
    • $550 a year if billed annually
  • Pro$80/month
    • 40 hours a month
    • 100GB storage
    • $880 a year if billed annually

Which should you pick?

Choose Cartesia if

  • You need sonic text-to-speech.
  • You want to start without paying.
  • You work on web, api.
  • You also want ink speech-to-text.
Cartesia review

Choose Sonix if

  • You need automated transcription.
  • You work on Web, API.
  • You also want translation.
Sonix review

Questions people ask

Is Cartesia or Sonix better?
Neither clearly leads. Cartesia starts at Free and Sonix at $10/month, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Cartesia or Sonix?
Cartesia has a free tier; the other does not. Paid plans start at Free for Cartesia and $10/month for Sonix.
Does Cartesia or Sonix run on more platforms?
Cartesia runs on web, api. Sonix runs on Web, API.
Can I use Cartesia for free?
Yes. Cartesia has a free tier, so you can try it without paying. Sonix starts at $10/month.
What is Cartesia best used for?
Cartesia is most often used for building low-latency voice agents for customer support, real-time transcription for conversational applications, voice cloning for branded synthetic voices, on-device or on-premise voice ai for regulated industries. Of those, building low-latency voice agents for customer support and real-time transcription for conversational applications are not what Sonix is typically brought in for.
What can Cartesia do that Sonix cannot?
Cartesia covers Sonic text-to-speech, Ink speech-to-text, Line voice agent platform, Instant and professional voice cloning. Sonix covers Automated transcription, Translation, Synchronised editor, Subtitle export.

Answered from the vendors’ own pages

Cartesia: What does Cartesia cost?

Cartesia offers a free plan, Pro at $4/month, Startup at $39/month, Scale at $239/month, and custom Enterprise pricing, each including a monthly credit allotment, with annual billing saving 20%.

Source
Sonix: What does Sonix cost per hour?

$10 an hour on pay-as-you-go, and $10 an hour for any usage beyond the monthly allowance on every subscription tier. That overage rate is published, which is unusual in this market.

Cartesia: Is there a free plan, and what are its limits?

The Free plan includes 20,000 credits per month, both TTS (Sonic) and STT (Ink), 2 concurrent TTS requests, 8 concurrent STT requests, and 1 voice agent slot.

Source
Sonix: Is there human transcription?

No. Sonix is automated transcription plus an editor for you to correct. If you need a contracted accuracy level, this is the wrong category of product.

Cartesia: How is usage metered?

Usage draws down a monthly credit allotment, with voice agent calls additionally billed at $0.06/minute and telephony via Cartesia phone numbers at $0.014/minute.

Source
Sonix: How accurate is it really?

The 99 percent claim assumes clean, single-speaker, standard-accent audio. Multi-speaker recordings with background noise land noticeably lower, and the cost shows up as your editing time.

Sonix: How many languages?

Transcription in over fifty languages and translation into a similar number, which is wider than most self-service competitors.

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