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Head-to-head comparison

Claude Sonnet 5 vs GPT-5.5

Claude Sonnet 5 (Anthropic) and GPT-5.5 (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 #26); and Claude Sonnet 5 is 3× cheaper per output token ($10.00/1M vs $30.00/1M).

Which should you choose?

Choose Claude Sonnet 5 if…

  • API cost matters — $10.00/1M output tokens against $30.00/1M, about 3× cheaper.
  • your workload is prompt-heavy — input tokens cost $2.00/1M against $5.00/1M.
  • you want provider choice — 5 listed API providers against 3.
  • Arena coding is your yardstick — 1520 against 1520.
  • LMArena Agent is your yardstick — 6.0% against 5.0%.
  • you want the more recently listed model — Claude Sonnet 5 was listed 30 June 2026, GPT-5.5 24 April 2026.

Choose GPT-5.5 if…

  • you want the stronger overall ModelCap Index position — #13 against #26 (82.5 vs 78.5 points).
  • AA Intelligence Index is your yardstick — 38.4 against 38.2.
  • AA Humanity's Last Exam is your yardstick — 45.8% against 41.3%.

Claude Sonnet 5 vs GPT-5.5: specs, pricing and context

Specification comparison of Claude Sonnet 5 and GPT-5.5
FieldClaude Sonnet 5AnthropicGPT-5.5OpenAI
ModelCap Index position#26#13
Index score78.582.5
EvidenceMeasuredMeasured
Input price / 1M tokens$2.00$5.00
Output price / 1M tokens$10.00$30.00
Context window1M tokens1M tokens
Max output tokens128K128K
API providers listed53
Weight accessAPI onlyAPI only
Input modalitiesText, Image, FileFile, Image, Text
First listed30 June 202624 April 2026
PublisherAnthropicOpenAI

Evidence: 4 public benchmark observations across 4 boards · 7 public benchmark observations across 7 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Claude Sonnet 5 vs GPT-5.5

Public benchmark boards where Claude Sonnet 5 or GPT-5.5 has a published result
BoardClaude Sonnet 5GPT-5.5Leads
Arena codingArena (LMArena)15201513–1527High15201514–1526HighClaude Sonnet 5
LMArena AgentLMArena6.0%4.4%–7.6%High5.0%4.1%–6.0%X-HighClaude Sonnet 5
ARC-AGI-2ARC Prize Foundation—85.0%X-HighOnly one result
ARC-AGI-3ARC Prize Foundation—0.4%HighOnly one result
AA Intelligence IndexArtificial Analysis38.2intelligence-index:v4.3:max38.4intelligence-index:v4.3:xhighGPT-5.5
AA τ²-Bench TelecomArtificial Analysis—93.9%tau2:telecom:dual-control:pass-at-1:3-repeats:source-model="GPT-5.5 (xhigh)":reasoning=trueOnly one result
AA Humanity's Last ExamArtificial Analysis41.3%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="Claude Sonnet 5 (Adaptive Reasoning, Max Effort)":reasoning=true45.8%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="GPT-5.5 (xhigh)":reasoning=trueGPT-5.5
Terminal-Bench 4.0Terminal-Bench (Laude Institute)12.4%9.4%–15.5%Claude Code · Max—Only one result
Terminal-Bench 2.1 Terminus 2Terminal-Bench—78.0X-HighOnly one result
WildClawBench OpenClawWildClawBench—58.2Only 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.

Claude Sonnet 5 vs GPT-5.5: common questions

Is Claude Sonnet 5 better than GPT-5.5?

GPT-5.5 ranks higher on the ModelCap Index as of 22 September 2026: #13 against #26. 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 overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.

Is Claude Sonnet 5 cheaper than GPT-5.5?

Claude Sonnet 5 is cheaper on output tokens: $10.00/1M against $30.00/1M. Input tokens are $2.00/1M for Claude Sonnet 5 and $5.00/1M for GPT-5.5. 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 $9.00 for Claude Sonnet 5 versus $25.00 for GPT-5.5. Claude Sonnet 5 costs 64.0% 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, Claude Sonnet 5 or GPT-5.5?

Both publish a 1M-token context window.

Which is better for coding, Claude Sonnet 5 or GPT-5.5?

Arena coding: Claude Sonnet 5 1520, GPT-5.5 1520 — Claude Sonnet 5 leads.

Are Claude Sonnet 5 and GPT-5.5 open-weight models?

Claude Sonnet 5: API only. GPT-5.5: 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 Claude Sonnet 5 and GPT-5.5?

ModelCap currently lists 5 API providers for Claude Sonnet 5 and 3 for GPT-5.5, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Claude Sonnet 5 vs GPT-5.5 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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