—per minute
—per hour
—per year
Realtime buys latency, not savings
Speech-to-speech models feel magical but audio tokens cost a premium. If cost matters more than latency, a cascaded pipeline wins — price it on the AI voice agent cost calculator.
What a minute of AI voice conversation costs
Speech-to-speech APIs bill audio tokens on both directions — roughly $0.06–$0.30 per conversation minute depending on model tier, which annualizes to painful numbers fast: a support bot handling 1,000 ten-minute calls monthly runs $600–$3,000 in model costs alone. The cascaded alternative (STT → LLM → TTS) costs $0.02–$0.08 per minute but adds 1–3 seconds of latency, which conversation UX research consistently flags as the threshold where users start talking over the bot. The realtime premium is a latency purchase — worth it for genuine dialogue, wasted on IVR-style menu flows.
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How this calculator works
The Realtime Voice API Cost Calculator estimates the monthly cost of running a speech-to-speech model, where spoken audio goes in and spoken audio comes back. You enter your expected conversation minutes per month and the per-minute rates for audio input and audio output, and it multiplies each rate by your usage to produce a total. The main drivers are volume and the input/output split: total minutes scale the whole bill linearly, while the balance between listening (input) and speaking (output) shifts the mix, since output minutes are typically priced higher than input.
The key trade-off to watch is that a single "conversation minute" usually bills as both input and output, so the effective cost per minute is closer to the two rates combined than to either one alone. Because cost rises directly with talk time, the biggest lever is design: shorter sessions, concise responses, and trimming silence or filler reduce billed minutes more reliably than chasing a lower per-minute rate. Model this before scaling so a growing user base does not quietly multiply your monthly spend.
Frequently asked questions
How much does a realtime voice API cost?
Realtime speech-to-speech models bill audio input and output separately per minute — together often $0.20–0.40/min. Multiply by your conversation minutes for the monthly bill.
Is realtime cheaper than STT + LLM + TTS?
Not usually. Realtime is lower-latency and simpler, but audio tokens are expensive. A cascaded pipeline (speech-to-text, then a text LLM, then text-to-speech) is often cheaper if you can accept slightly more latency.