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Head-to-head comparison

GPT-5.5 vs o3

GPT-5.5 (OpenAI) and o3 (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 22 September 2026

As of 22 September 2026, GPT-5.5 holds the stronger ModelCap Index position (#13 vs #53); o3 is 3.8× cheaper per output token ($8.00/1M vs $30.00/1M); and GPT-5.5 offers the longer context window (1M vs 200K tokens).

Which should you choose?

Choose GPT-5.5 if…

  • you want the stronger overall ModelCap Index position — #13 against #53 (82.5 vs 66.5 points).
  • you need the longer context window — 1M tokens against 200K.
  • you want provider choice — 3 listed API providers against 1.
  • Arena coding is your yardstick — 1520 against 1460.
  • ARC-AGI-2 is your yardstick — 85.0% against 6.5%.
  • AA τ²-Bench Telecom is your yardstick — 93.9% against 80.7%.
  • AA Humanity's Last Exam is your yardstick — 45.8% against 20.1%.
  • you want the more recently listed model — GPT-5.5 was listed 24 April 2026, o3 16 April 2025.

Choose o3 if…

  • API cost matters — $8.00/1M output tokens against $30.00/1M, about 3.8× cheaper.
  • your workload is prompt-heavy — input tokens cost $2.00/1M against $5.00/1M.

GPT-5.5 vs o3: specs, pricing and context

Specification comparison of GPT-5.5 and o3
FieldGPT-5.5OpenAIo3OpenAI
ModelCap Index position#13#53
Index score82.566.5
EvidenceMeasuredMeasured
Input price / 1M tokens$5.00$2.00
Output price / 1M tokens$30.00$8.00
Context window1M tokens200K tokens
Max output tokens128K100K
API providers listed31
Weight accessAPI onlyAPI only
Input modalitiesFile, Image, TextImage, Text, File
First listed24 April 202616 April 2025
PublisherOpenAIOpenAI

Evidence: 7 public benchmark observations across 7 boards · 3 public benchmark observations across 3 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: GPT-5.5 vs o3

Public benchmark boards where GPT-5.5 or o3 has a published result
BoardGPT-5.5o3Leads
Arena codingArena (LMArena)15201514–1526High14601454–1467GPT-5.5
LMArena AgentLMArena5.0%4.1%–6.0%X-High—Only one result
ARC-AGI-2ARC Prize Foundation85.0%X-High6.5%HighGPT-5.5
ARC-AGI-3ARC Prize Foundation0.4%High—Only one result
SWE-benchSWE-bench (Princeton / SWE-agent team)—58.4%Only one result
BFCL V4UC Berkeley (Gorilla)—63.1PromptOnly one result
AA Intelligence IndexArtificial Analysis38.4intelligence-index:v4.3:xhigh—Only one result
AA τ²-Bench TelecomArtificial Analysis93.9%tau2:telecom:dual-control:pass-at-1:3-repeats:source-model="GPT-5.5 (xhigh)":reasoning=true80.7%tau2:telecom:dual-control:pass-at-1:3-repeats:source-model="o3":reasoning=trueGPT-5.5
AA Humanity's Last ExamArtificial Analysis45.8%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="GPT-5.5 (xhigh)":reasoning=true20.1%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="o3":reasoning=trueGPT-5.5
Terminal-Bench 2.1 Terminus 2Terminal-Bench78.0X-High—Only one result
WildClawBench OpenClawWildClawBench58.2—Only one result

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

GPT-5.5 vs o3: common questions

Is GPT-5.5 better than o3?

GPT-5.5 ranks higher on the ModelCap Index as of 22 September 2026: #13 against #53. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals do not overlap, but the aggregate Index does not predict performance on every task; compare the relevant benchmark configurations before choosing.

Is GPT-5.5 cheaper than o3?

o3 is cheaper on output tokens: $8.00/1M against $30.00/1M. Input tokens are $5.00/1M for GPT-5.5 and $2.00/1M for o3. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $25.00 for GPT-5.5 versus $8.00 for o3. o3 costs 68.0% less in this scenario. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.

Which has the bigger context window, GPT-5.5 or o3?

GPT-5.5 has the larger context window: 1M tokens against 200K.

Which is better for coding, GPT-5.5 or o3?

Arena coding: GPT-5.5 1520, o3 1460 — GPT-5.5 leads.

Are GPT-5.5 and o3 open-weight models?

GPT-5.5: API only. o3: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run GPT-5.5 and o3?

ModelCap currently lists 3 API providers for GPT-5.5 and 1 for o3, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this GPT-5.5 vs o3 comparison?

Every figure comes from the sealed ModelCap dataset published 22 September 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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