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Head-to-head comparison

GPT-5.5 vs o3 Pro

GPT-5.5 (OpenAI) and o3 Pro (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 17 August 2026

As of 17 August 2026, GPT-5.5 holds the stronger ModelCap Index position (#8 vs #54); GPT-5.5 is 2.7× cheaper per output token ($30.00/1M vs $80.00/1M); 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 — #8 against #54 (76.9 vs 46.5 points).
  • API cost matters — $30.00/1M output tokens against $80.00/1M, about 2.7× cheaper.
  • your workload is prompt-heavy — input tokens cost $5.00/1M against $20.00/1M.
  • you need the longer context window — 1M tokens against 200K.
  • you want provider choice — 3 listed API providers against 1.
  • Artificial Analysis Intelligence Index is your yardstick — 56.3 against 33.3.
  • you want the more recently listed model — GPT-5.5 was listed 24 April 2026, o3 Pro 10 June 2025.

Choose o3 Pro if…

  • ModelCap publishes no field on which o3 Pro leads GPT-5.5 for this pair.

GPT-5.5 vs o3 Pro: specs, pricing and context

Specification comparison of GPT-5.5 and o3 Pro
FieldGPT-5.5OpenAIo3 ProOpenAI
ModelCap Index position#8#54
Index score76.946.5
EvidenceMeasuredMeasured
Input price / 1M tokens$5.00$20.00
Output price / 1M tokens$30.00$80.00
Context window1M tokens200K tokens
Max output tokens128K100K
API providers listed31
Weight accessAPI onlyAPI only
Input modalitiesFile, Image, TextText, File, Image
First listed24 April 202610 June 2025
PublisherOpenAIOpenAI

Evidence: 6 public benchmark observations across 6 boards · 1 public benchmark observation across 1 board. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: GPT-5.5 vs o3 Pro

Public benchmark boards where GPT-5.5 or o3 Pro has a published result
BoardGPT-5.5o3 ProLeads
Arena codingArena (LMArena)15201513–1526High—Only one result
LMArena AgentLMArena8.9%7.9%–9.9%X-High—Only one result
ARC-AGI-2ARC Prize Foundation85.0%X-High—Only one result
ARC-AGI-3ARC Prize Foundation0.4%High—Only one result
Artificial Analysis Intelligence IndexArtificial Analysis56.3intelligence-index33.3intelligence-indexGPT-5.5

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 Pro: common questions

Is GPT-5.5 better than o3 Pro?

GPT-5.5 ranks higher on the ModelCap Index as of 17 August 2026: #8 against #54. 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.

Is GPT-5.5 cheaper than o3 Pro?

GPT-5.5 is cheaper on output tokens: $30.00/1M against $80.00/1M. Input tokens are $5.00/1M for GPT-5.5 and $20.00/1M for o3 Pro. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens.

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

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

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

The two models do not share a coding benchmark board on ModelCap yet, so no head-to-head coding score is published; the ModelCap Index position is the closest overall signal.

Are GPT-5.5 and o3 Pro open-weight models?

GPT-5.5: API only. o3 Pro: 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 Pro?

ModelCap currently lists 3 API providers for GPT-5.5 and 1 for o3 Pro, 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 Pro comparison?

Every figure comes from the sealed ModelCap dataset published 17 August 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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