GPT-5.1 vs GPT-3.5 Turbo Instruct
API pricing, benchmark indices and specs — updated 19 October 2026.
openai · A · API-only
Input / 1M
$1.25
Output / 1M
$10.00
AA index
24.7
proprietary · 400K context
openai · B · API-only
Input / 1M
$1.50
Output / 1M
$2.00
AA index
—
proprietary · 4.1K context
Specification comparison
Differences are highlighted; identical values are muted.
| Specification | GPT-5.1 | GPT-3.5 Turbo Instruct |
|---|---|---|
| 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 | 400,000 | 4,095 |
| 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 | $1.25 | $1.50 |
| API output price / 1M tokens | $10.00 | $2.00 |
| Est. cost per 1M input + 1M output tokens | $11.25 | $3.50 |
| Cached input / 1M tokens | $0.13 | — |
| AA Intelligence Index | 24.7 | — |
| AA Coding Index | 49.4 | — |
| AA Agentic Index | — | — |
| Max output tokens | 128,000 | 3,685 |
| API providers | 2 | 1 |
| Tool calling | Yes | No |
| Reasoning mode | Yes | No |
API cost
Estimated cost of 1M input + 1M output tokens via OpenRouter
GPT-5.1
$11.25
GPT-3.5 Turbo Instruct
$3.50
GPT-3.5 Turbo Instruct is 3.2× cheaper at list price.