Cartesia Line pricing (2026): per-minute costs, plan limits, and a worked example

Cartesia Line combines a voice-agent usage charge, telephony charges, and a monthly plan. Its published call-duration rate is $0.06/minute, plus $0.014/minute when using a Cartesia-provided phone number. That produces a $0.074/minute usage floor while eligible LLM usage remains free. Cartesia pricing, accessed 2026-09-10.

The qualification matters: Cartesia describes LLM usage as “Free for UI-created agents for a limited time.” No end date or replacement rate is published on the fetched pricing pages. This guide separates the computable usage floor from plan fees and unresolved billing details.

How Cartesia Line's pricing model works

Start with call duration, add telephony for a Cartesia number, then add your plan fee. The temporary LLM waiver applies specifically to UI-created agents. The public wording does not establish equivalent treatment for API-, SDK-, or code-created agents.

The plan ladder also controls simultaneous calls:

Source: Cartesia pricing, accessed 2026-09-10.

Concurrency measures calls happening at the same time, rather than monthly call volume. A concentrated traffic peak can require a higher plan even when total minutes are modest. Conversely, a large monthly workload does not alone establish which concurrency tier you need.

The pricing page also shows credits and Sonic speech-generation allowances. Do not treat those allowances as included Line call minutes. The fetched pages do not establish a conversion that lets us deduct them from the agent bill.

Cartesia's Line documentation pricing page redirected to login during our September 10, 2026 check. Its gated contents cannot resolve the public pricing ambiguities here. The calculations below rely on the public pricing page.

What's included vs. billed separately

Source: Cartesia pricing, accessed 2026-09-10.

Cartesia makes the call-duration and hosted telephony arithmetic straightforward. The uncertainty lies in scope and future terms. An absent speech line item supports an inference of inclusion, but does not establish a contractual guarantee.

Worked example: 10,000 minutes a month

Use 2,000 calls × 5 connected minutes = 10,000 connected minutes/month, one primary included language, and one phone number. Exclude transfers, hold, and voicemail minutes. Peak concurrency is at most 10 calls.

For Cartesia, assume a UI-created agent using a Cartesia-provided number while the LLM waiver applies. This is illustrative planning arithmetic, not a quote. Language eligibility needs confirmation for the chosen configuration.

Derived from Cartesia pricing, accessed 2026-09-10.

Add the plan separately:

Derived from Cartesia pricing, accessed 2026-09-10. These are usage-plus-plan subtotals, before any unverified number rental, billing adjustments, or other applicable charges.

Pro is the lowest listed plan whose concurrency allowance covers the workload if peaks reach its assumed maximum. The Free row is conditional arithmetic, not confirmation that this workload is purchasable on Free. Public evidence does not clearly establish how the agent rate applies there.

When the LLM waiver ends, the calculation becomes agent usage plus telephony plus plan fee plus the applicable LLM charge. That future charge and resulting total are not computable from the public page. There is no supported date or rate to substitute into the example.

Gotcha checklist

• Treat free LLM usage as temporary. Ask for the end date, replacement billing basis, and notice process before committing a recurring budget.
• Check how the agent was created. The waiver names UI-created agents. API-created or code-created agents need their own billing confirmation; do not assume the same subtotal applies.
• Size concurrency against peaks. Monthly minutes cannot tell you whether a plan will handle overlapping calls. Check the plan table against your busiest period.
• Keep speech allowances separate. Sonic generation minutes are not verified Line call allowances. Do not subtract them from agent usage without an explicit conversion rule.
• Resolve metering before comparing invoices. The public evidence does not state the agent billing increment. Short calls may not match simple connected-minute arithmetic.
• Ask for the gated pricing details. The Line pricing documentation requires login. Confirm speech inclusion, number rental, Free-plan eligibility, and eventual evaluation charges before relying on a complete monthly total.

How ThunderPhone prices differ

ThunderPhone uses prepaid, pay-as-you-go engine pricing with no subscription, seat, or platform fee. Each engine includes speech recognition, the language model, and voice. Its published engine structure does not depend on a temporary LLM waiver.

Source: ThunderPhone pricing, accessed 2026-09-10.

Telephony is separate from those engine rates. Imported VoIP/SIP numbers have no ThunderPhone import or monthly charge; the carrier bills its own usage. Premium voice or language paths add up to 3¢/minute, non-stacking, or up to $300 for this workload. Other configured add-ons can change the rate shown in the builder before launch.

ThunderPhone publishes no per-line concurrency fee. That does not establish an unlimited capacity guarantee. Cartesia's explicit plan limits provide a clearer published capacity ladder for buyers planning simultaneous calls.

Compare matching components: Cartesia's example includes its stated phone usage charge, while ThunderPhone's engine totals require setup-dependent telephony. See ThunderPhone pricing explained, AI phone agent cost, and the voice AI cost breakdown.

For broader comparisons, use the cheapest AI voice agent guide, voice AI pricing comparison, and voice AI price index.

FAQ

How much does Cartesia Line cost per minute?

The computed usage floor is $0.074/minute for a UI-created agent using a Cartesia number during the LLM waiver. That combines agent and telephony charges. Plan fees and unresolved billing items remain separate. Cartesia pricing, accessed 2026-09-10.

Is Cartesia Line's LLM usage permanently free?

No; the published waiver is limited-time and specifically covers UI-created agents. No end date or replacement rate is published on the fetched pages. Post-waiver arithmetic is not computable.

Does the free LLM offer cover API-created agents?

The public wording does not confirm coverage for API-created agents. Obtain billing terms for the creation path you actually use before applying the example subtotal.

What would 10,000 minutes cost on Cartesia Line?

The example computes to $740 in usage, or $745 including Pro's monthly fee, subject to the stated qualifications. Pro accommodates the assumed concurrency peak. This is not a verified invoice total. Cartesia pricing, accessed 2026-09-10.

Where can I verify Line pricing and concurrency limits?

The public Cartesia pricing page lists rates and plan limits; the Line pricing documentation redirected to login. Use the public table for initial planning, then obtain the gated terms for unresolved billing questions.

Sources and freshness

• Cartesia pricing, accessed 2026-09-10: agent rates, telephony, temporary waivers, plan fees, and concurrency limits.
• Cartesia Line pricing documentation, accessed 2026-09-10: redirected to login; gated contents were not verified.
• ThunderPhone pricing, accessed 2026-09-10: engine pricing, included components, premium paths, and telephony treatment.

Every third-party figure on this page was checked against the linked first-party pages on September 10, 2026. It is documentation-based; no account, invoice, or live call was tested. Unresolved items include waiver expiry and replacement charges, API-created agent billing, explicit speech inclusion, Free-plan agent billing, number rental, and metering.