How much does the GPT-5.5 API cost?

GPT-5.5 costs $5 per million input tokens and $30 per million output tokens, with cached input at $0.5 per million. A workload of 10M input and 1.5M output tokens per month costs about $95.00.

What is the context window of GPT-5.5?

GPT-5.5 supports a context window of 1,000,000 tokens (1M), with up to 128K output tokens per response.

Is GPT-5.5 open source?

No — GPT-5.5 is a proprietary model available through OpenAI's API and partner platforms.

What are the best alternatives to GPT-5.5?

The closest alternatives by overall capability are Qwen3-Max, Gemini 3 Pro, Gemini 2.5 Pro, DeepSeek V3.2. See the comparison pages for detailed head-to-head breakdowns.

GPT-5.5

Name: GPT-5.5
Price: 5 USD
Author: OpenAI

OpenAI·Apr 2026reasoningproprietary

77.2

modhub Index

GPT-5.5 is OpenAI's flagship model, released in April 2026 as the successor to the GPT-5.x line. It pairs a 1M-token context window with adaptive reasoning effort, and posts top-tier results on agentic coding benchmarks like SWE-bench Verified. Prompts beyond 272K input tokens are billed at a long-context premium, so cost planning matters for huge-context workloads. It is the default choice in ChatGPT and OpenAI's recommended model for complex multi-step tasks.

Benchmark results

Where it shines

Frontier-level agentic coding and tool use
1M-token context window for whole-repo and long-document work
Adaptive reasoning effort balances latency against quality
First-class support across the OpenAI ecosystem (Responses API, Codex)

Alternatives to GPT-5.5

Qwen3-Max

Alibaba's trillion-parameter API flagship — frontier-adjacent quality with strong agentic tool use at mid-tier prices.

Gemini 3 Pro

Google's November 2025 frontier breakout — 91.9% GPQA Diamond and 37.5% HLE made it the reasoning leader of its generation.

Gemini 2.5 Pro

Google's 2025 workhorse flagship — first mainstream thinking model with a 1M context, still widely deployed.

DeepSeek V3.2

The sparse-attention release that halved DeepSeek's already-lowest-in-class prices while keeping GPT-class quality.

Frequently asked questions

How much does the GPT-5.5 API cost?: GPT-5.5 costs $5 per million input tokens and $30 per million output tokens, with cached input at $0.5 per million. A workload of 10M input and 1.5M output tokens per month costs about $95.00.
What is the context window of GPT-5.5?: GPT-5.5 supports a context window of 1,000,000 tokens (1M), with up to 128K output tokens per response.
Is GPT-5.5 open source?: No — GPT-5.5 is a proprietary model available through OpenAI's API and partner platforms.
What are the best alternatives to GPT-5.5?: The closest alternatives by overall capability are Qwen3-Max, Gemini 3 Pro, Gemini 2.5 Pro, DeepSeek V3.2. See the comparison pages for detailed head-to-head breakdowns.