Is GPT-4o or GPT-5.5 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 128K for GPT-4o.

Is GPT-4o or GPT-5.5 better for coding?

Both GPT-4o and GPT-5.5 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-4o and GPT-5.5 released?

GPT-4o was released by OpenAI on 2024-05-13. GPT-5.5 was released by OpenAI on 2026-03-01.

Is GPT-4o or GPT-5.5 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 128K for GPT-4o.

Is GPT-4o or GPT-5.5 better for coding?

Both GPT-4o and GPT-5.5 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-4o and GPT-5.5 released?

GPT-4o was released by OpenAI on 2024-05-13. GPT-5.5 was released by OpenAI on 2026-03-01.

GPT-4o vs GPT-5.5

A complete head-to-head: pricing, context window, benchmarks, modality coverage, and openness, with a programmatic verdict synthesized from the underlying data.

UpdatedApr 30, 2026

GPT-4o specs · GPT-5.5 specs

Verdict by category

PriceGPT-4o
GPT-4o publishes pricing ($10.00 / 1M output tokens) while GPT-5.5 does not.
Context windowGPT-5.5
GPT-5.5 accepts 400K tokens vs 128K, 3.1× 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.
ModalitiesTie
Both handle text, vision, audio.
OpennessTie
Both are closed-weight, API-only.

It's a genuine coin-flip between GPT-4o and GPT-5.5: 1 category wins each, with the rest tied. GPT-4o publishes pricing ($10.00 / 1M output tokens) while GPT-5.5 does not. GPT-5.5 accepts 400K tokens vs 128K, 3.1× the room for long documents and codebases.

No directly comparable public benchmarks are available for both models, check the spec sheets for individual scores. Both target the same set of modalities (text, vision, audio), so the deciding factors are price, context, and raw quality. Both are closed-weight, API-only.

GPT-5.5 is the newer of the two, released 22 months after GPT-4o, which usually means a more recent knowledge cutoff and updated safety post-training. GPT-4o is usually picked for chatbots and vision workloads, while GPT-5.5 sees more deployments in agents and tool use. If pricing matters more than every last benchmark point, run the numbers in the calculator below before committing.

Side-by-side specs

Spec	GPT-4o	GPT-5.5
Provider	OpenAI	OpenAI
Released	May 2024	Mar 2026
Modalities	text, vision, audio	text, vision, audio
Context window	128K tokens	400K tokens
Max output	,	,
Input · 1M	$2.50 / 1M tokens	Pricing not published
Output · 1M	$10.00 / 1M tokens	Pricing not published
Knowledge cutoff	2023-10	,
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$22.50 vs ,
Heavy usage, 1M in / 500k out per day$225 vs ,
RAG workload, 5M in / 200k out per day$435 vs ,

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).

Price calculator

Estimated spend for the listed models at your usage. Numbers are derived from each model's published per-million-token rates.

Input tokens / dayOutput tokens / dayHorizon

GPT-4o$0.750
GPT-5.5Pricing unavailable

Benchmarks compared

Only sourced numbers. Where a benchmark is missing for one model we show the available value rather than fabricating the other.

GPT-4oGPT-5.5

MMLU88.7
HumanEval90.2

Pick GPT-4o if

GPT-4o fits when…

Native multimodal
Mature SDK and tooling

Pick GPT-5.5 if

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 128K for GPT-4o.

Don't want either?

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.

See GPT-5 specs GPT-4o vs GPT-5 GPT-5.5 vs GPT-5

Frequently asked

Is GPT-4o or GPT-5.5 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 128K for GPT-4o.
Is GPT-4o or GPT-5.5 better for coding?
Both GPT-4o and GPT-5.5 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-4o and GPT-5.5 released?
GPT-4o was released by OpenAI on 2024-05-13. GPT-5.5 was released by OpenAI on 2026-03-01.

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