GPT-5.5 vs o3
A complete head-to-head: pricing, context window, benchmarks, modality coverage, and openness, with a programmatic verdict synthesized from the underlying data.
Updated
GPT-5.5 specs · o3 specs- Priceo3
o3 publishes pricing ($8.00 / 1M output tokens) while GPT-5.5 does not.
- Context windowGPT-5.5
GPT-5.5 accepts 400K tokens vs 200K, 2.0× the room for long documents and codebases.
- BenchmarksTie
No directly comparable public benchmarks are available for both models, check the spec sheets for individual scores.
- ModalitiesGPT-5.5
GPT-5.5 supports 3 modalities (text, vision, audio) vs 2 for o3.
- OpennessTie
Both are closed-weight, API-only.
On balance GPT-5.5 edges ahead, winning 2 of 5 categories against o3's 1. o3 publishes pricing ($8.00 / 1M output tokens) while GPT-5.5 does not. GPT-5.5 accepts 400K tokens vs 200K, 2.0× the room for long documents and codebases.
No directly comparable public benchmarks are available for both models, check the spec sheets for individual scores. They differ in modality coverage, GPT-5.5 handles text, vision, audio while o3 handles text, vision, which can be the deciding factor before you even look at benchmarks. Both are closed-weight, API-only.
GPT-5.5 is the newer of the two, released 11 months after o3, which usually means a more recent knowledge cutoff and updated safety post-training. GPT-5.5 is usually picked for agents and tool use workloads, while o3 sees more deployments in reasoning and math. If pricing matters more than every last benchmark point, run the numbers in the calculator below before committing.
Side-by-side specs
| Spec | GPT-5.5 | o3 |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Released | Mar 2026 | Apr 2025 |
| Modalities | text, vision, audio | text, vision |
| Context window | 400K tokens | 200K tokens |
| Max output | , | , |
| Input · 1M | Pricing not published | $2.00 / 1M tokens |
| Output · 1M | Pricing not published | $8.00 / 1M tokens |
| Knowledge cutoff | , | 2024-06 |
| Open weights | No | No |
| API available | Yes | Yes |
Pricing at scale
What you'd actually pay at typical workloads. Numbers come from each model's published per-million-token rates.
- Light usage, 100k in / 50k out per day, vs $18.00
- Heavy usage, 1M in / 500k out per day, vs $180
- RAG workload, 5M in / 200k out per day, vs $348
Light usage, 100k in / 50k out per day: pricing not directly comparable (one or both models are missing public per-token rates). Heavy usage, 1M in / 500k out per day: pricing not directly comparable (one or both models are missing public per-token rates). RAG workload, 5M in / 200k out per day: pricing not directly comparable (one or both models are missing public per-token rates).
Estimated spend for the listed models at your usage. Numbers are derived from each model's published per-million-token rates.
- GPT-5.5Pricing unavailable
- o3$0.600
Benchmarks compared
Only sourced numbers. Where a benchmark is missing for one model we show the available value rather than fabricating the other.
- HumanEval,95.0
- GPQA,87.7
GPT-5.5 fits when…
- Industry-leading tool-use and function-calling reliability
- Strong end-to-end agent performance across SWE-bench and GAIA
- Wide ecosystem support, ChatGPT, Realtime API, Responses API
- Long-context tasks, handles 400K tokens vs 200K for o3.
- Multimodal needs covering audio.
o3 fits when…
- Industry-leading reasoning depth at launch
- Strong on math, science, and abstract puzzles
- Tool-use during reasoning loops
Consider GPT-5
OpenAI's unified flagship combining GPT-line breadth with built-in reasoning, replacing both GPT-4o and the o-series for most users.
Frequently asked
Is GPT-5.5 or o3 cheaper?
Per-token pricing isn't published for at least one of these models, check each model's spec page for current rates.Which has the larger context window?
GPT-5.5 accepts 400K tokens vs 200K for o3.Is GPT-5.5 or o3 better for coding?
Both GPT-5.5 and o3 are competitive on coding benchmarks. See each model's individual spec page for HumanEval and SWE-bench scores where published. For an opinionated pick, consult our Best LLM for Coding ranking.Are either of these models open source?
Neither model ships open weights, both are accessible only via their respective providers' APIs.When were GPT-5.5 and o3 released?
GPT-5.5 was released by OpenAI on 2026-03-01. o3 was released by OpenAI on 2025-04-16.
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