# GPT-5.5 vs Claude Sonnet 5

On provider list prices, Claude Sonnet 5 costs $3 per million input tokens against $5 for GPT-5.5: 1.7x apart. Output is $15 against $30 (2.0x).

## Specifications

| | GPT-5.5 | Claude Sonnet 5 |
| --- | --- | --- |
| Lab | OpenAI | Anthropic |
| Access | API only | API only |
| Context window | 400K tokens | 1M tokens |
| List price, input | $5 / M tokens | $3 / M tokens |
| List price, output | $30 / M tokens | $15 / M tokens |
| Cached input | $0.50 / M tokens | n/a |
| License | Proprietary API | Proprietary API |
| Fine-tunable | No | No |

Specifications and provider list prices from the Allocate catalog, checked 2026-07-21.

## What the numbers say

Take 1,000,000 requests a month at 1,200 input and 350 output tokens each. That workload costs $8,850 a month on Claude Sonnet 5 and $16,500 on GPT-5.5 at list: a gap of $7,650, or 1.9x.

Claude Sonnet 5 reads 1M tokens per request against 400K for GPT-5.5, 2.5x the window. That decides which one can take whole documents without splitting them.

## Choose GPT-5.5 for

- Complex tool-using agents
- Code generation
- General assistants

## Choose Claude Sonnet 5 for

- Judgment calls with policy context
- Customer-facing writing
- Review and escalation flows

## Common questions

### Which is cheaper, GPT-5.5 or Claude Sonnet 5?

Claude Sonnet 5, on this workload shape. At list prices it is $3/$15 per million tokens in and out against $5/$30 for GPT-5.5. Billed on Allocate: $3.21/$16.05 against $5.35/$32.10.

### Which has the bigger context window?

Claude Sonnet 5: 1,000,000 tokens (1M) against 400,000 (400K) for GPT-5.5.

### Can I fine-tune GPT-5.5 or Claude Sonnet 5?

No. Both are closed models served over API. If you want a model you can train and own, start from an open-weights base in the catalog.

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[HTML page](https://allocate.network/compare/gpt-5-5-vs-sonnet-5) · [GPT-5.5](https://allocate.network/models/gpt-5-5.md) · [Claude Sonnet 5](https://allocate.network/models/sonnet-5.md) · [Machine-readable catalog](https://allocate.network/catalog.json)