GPT-5.5 vs GPT-5 Pro
API pricing, benchmark indices and specs — updated 19 October 2026.
openai · A · API-only
Input / 1M
$5.00
Output / 1M
$30.00
AA index
38.4
proprietary · 1.0M context
openai · B · API-only
Input / 1M
$15.00
Output / 1M
$120.00
AA index
—
proprietary · 400K context
Specification comparison
Differences are highlighted; identical values are muted.
| Specification | GPT-5.5 | GPT-5 Pro |
|---|---|---|
| Deployment | API-only (closed weights) | API-only (closed weights) |
| Parameters | n/a — API-only | n/a — API-only |
| Architecture | n/a — API-only | n/a — API-only |
| Context length | 1,050,000 | 400,000 |
| Licence | Proprietary | Proprietary |
| Commercial use | Per API terms | Per API terms |
| Languages | n/a — API-only | n/a — API-only |
| Downloads 30d | n/a — API-only | n/a — API-only |
| Downloads all time | n/a — API-only | n/a — API-only |
| Quantizations on the Hub | n/a — API-only | n/a — API-only |
| Gated | n/a — API-only | n/a — API-only |
| First seen on the Hub | n/a — API-only | n/a — API-only |
| API input price / 1M tokens | $5.00 | $15.00 |
| API output price / 1M tokens | $30.00 | $120.00 |
| Est. cost per 1M input + 1M output tokens | $35.00 | $135.00 |
| Cached input / 1M tokens | $0.50 | — |
| AA Intelligence Index | 38.4 | — |
| AA Coding Index | 74.9 | — |
| AA Agentic Index | 36.4 | — |
| Max output tokens | 128,000 | 128,000 |
| API providers | 3 | 1 |
| Tool calling | Yes | Yes |
| Reasoning mode | Yes | Yes |
API cost
Estimated cost of 1M input + 1M output tokens via OpenRouter
GPT-5.5
$35.00
GPT-5 Pro
$135.00
GPT-5.5 is 3.9× cheaper at list price.