> ## Documentation Index
> Fetch the complete documentation index at: https://docs.thinnest.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Pricing

> Aero TTS pricing, per-model rates, and billing details.

# Pricing

Aero TTS uses a simple pay-as-you-go pricing model. You are billed per character synthesized, deducted from your thinnestAI wallet balance.

## Plan Details

Every thinnestAI account gets one flat pricing plan with all features included:

|                             | Details          |
| --------------------------- | ---------------- |
| **Free Monthly Characters** | 10,000           |
| **Rate Limit**              | 500 requests/min |
| **Max Characters/Request**  | 10,000           |
| **Voice Lab**               | Included         |
| **Streaming**               | Included         |
| **WebSocket**               | Included         |

## Per-Model Rates

Each model has its own rate per million characters:

| Model       | Rate (per 1M chars) | Best For                        |
| ----------- | ------------------- | ------------------------------- |
| `aero`      | \$10.00             | Highest quality, lowest latency |
| `aero-mini` | \$2.00              | Cost-effective batch processing |
| `aero-nano` | \$0.50              | Lightweight, minimal resources  |

## How Billing Works

1. You send a synthesis request with text.
2. Aero TTS counts the characters in your text.
3. The cost is calculated based on the model you selected.
4. The amount is deducted from your thinnestAI wallet balance.
5. Audio is returned.

If your balance is insufficient, you receive a `402 Payment Required` error.

## Checking Your Balance

Your wallet balance is shared with the rest of the thinnestAI platform (chat, voice calls, etc.).

```bash theme={null}
curl https://api.thinnest.ai/api/billing/balance \
  -H "Authorization: Bearer thns_sk_YOUR_KEY"
```

## Topping Up

Add funds to your wallet through the **Billing** page in the dashboard, or via API:

```bash theme={null}
curl -X POST https://api.thinnest.ai/api/billing/topup \
  -H "Authorization: Bearer thns_sk_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "amount": 10.00 }'
```

## Usage Tracking

Monitor your TTS spending in the dashboard under **Aero TTS > Usage**, or via the API:

```bash theme={null}
curl "https://api.thinnest.ai/api/tts/usage?period=month" \
  -H "Authorization: Bearer thns_sk_YOUR_KEY"
```

The response includes total characters, request counts, top voices, and daily breakdowns.

## Cost Estimates

| Content                  | Characters | Cost (aero) | Cost (aero-nano) |
| ------------------------ | ---------- | ----------- | ---------------- |
| Short greeting           | \~50       | \$0.0005    | \$0.000025       |
| Support response         | \~300      | \$0.003     | \$0.00015        |
| Email read-aloud         | \~2,000    | \$0.02      | \$0.001          |
| Blog post narration      | \~5,000    | \$0.05      | \$0.0025         |
| 1-hour audiobook chapter | \~80,000   | \$0.80      | \$0.04           |

At the `aero` rate (\$10/million characters), 1 million characters is enough for approximately 3,000-4,000 typical voice agent responses.

## Free Allowance

Every thinnestAI account gets 10,000 free characters per month (resets on the 1st of each month). This lets you test and prototype without any charges.