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Comparison · 2 models · Updated Oct 4, 2026

GPT-5.5 vs GPT-6 Astra

GPT-6 Astra comes out ahead, 68 to 63 on our weighted score, though GPT-5.5 is 44% cheaper per token.

  1. OpenAI

    GPT-5.5

    Released Apr 23, 2026

    63/100
    • ECI159.2
    • Price$5.00 / $30.00
    • Context1.05M
    Full specs Remove GPT-5.5
  2. Our pick

    OpenAI

    GPT-6 Astra

    Released Sep 4, 2026

    68/100
    • ECI166.5
    • Price$10.00 / $50.00
    • Context1.05M
    Full specs Remove GPT-6 Astra

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

GPT-6 Astra is our pick

GPT-6 Astra is the better all-round choice, scoring 68/100 against GPT-5.5 (63). It leads on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGPT-6 AstraCapabilities Index (ECI): GPT-6 Astra 166.5 · GPT-5.5 159.2
  • Lowest priceGPT-5.5GPT-5.5 $11.25 · GPT-6 Astra $20.00 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameGPT-5.5 1,050,000 · GPT-6 Astra 1,050,000 tokens
  • Widest inputsSame inputsGPT-5.5: Text, Images, PDFs · GPT-6 Astra: Text, Images, PDFs
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGPT-5.5GPT-6 Astra
CapabilityCapabilities Index (ECI)50%9099
Price25%00
Inputs & features15%8080
Context window10%6161
Overall100%63/10068/100
02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

GPT-5.5 vs GPT-6 Astra specifications side by side
SpecificationGPT-5.5OpenAIGPT-6 AstraOpenAI
Capability
Capabilities Index (ECI)159.2166.5 (best)
ECI rank#10 of 148#2 of 148 (best)
GPQA DiamondGraduate-level science questions94.0%95.8% (best)
FrontierMath Tiers 1–3Research-level mathematics85.3%93.7% (best)
OTIS Mock AIME 2024–2025Competition mathematics100%100%
SWE-bench VerifiedFixing real GitHub issues80.6%—
SimpleQA VerifiedShort factual questions63.0%75.6% (best)
Price per million tokens
Input$5.00 (best)$10.00
Output$30.00 (best)$50.00
Cached input$0.50 (best)$1.00
Blended (3:1)$11.25 (best)$20.00
Long-context rateOver 272K: $10.00 / $45.00Over 272K: $20.00 / $75.00
Price sourceOfficial OpenAI APIOfficial OpenAI API
Limits
Context window1,050,000 tokens1,050,000 tokens
Max output128,000 tokens128,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoNo
VideoNoNo
ReasoningYeslow · medium · high · xhighYeslow · medium · high · xhigh · max
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDgpt-5.5gpt-6-astra
API providers42 (best)26
ReleasedApr 23, 2026Sep 4, 2026
Knowledge cutoffDec 1, 2025Apr 30, 2026
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • GPT-5.5$110.00
  • GPT-6 Astra$200.00
04 — Questions

Which should you choose?

Which is better: GPT-5.5 or GPT-6 Astra?

GPT-6 Astra is the better all-round choice, scoring 68/100 against GPT-5.5 (63). It leads on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, GPT-5.5 or GPT-6 Astra?

GPT-5.5 is cheaper at $5.00 input / $30.00 output per million tokens (official OpenAI API price). GPT-6 Astra costs $10.00 input / $50.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $11.25 per million tokens for GPT-5.5 versus $20.00 for GPT-6 Astra (1.8× as much).

Which scores higher on benchmarks?

GPT-6 Astra scores higher on the Capabilities Index (ECI): GPT-6 Astra 166.5 (#2 of 148) and GPT-5.5 159.2 (#10 of 148). Their confidence ranges do not overlap (163.1–171.1 vs 156.9–162.4), so the gap is a real one. On individual benchmarks: GPQA Diamond — GPT-6 Astra 95.8%, GPT-5.5 94.0%; FrontierMath Tiers 1–3 — GPT-6 Astra 93.7%, GPT-5.5 85.3%; OTIS Mock AIME 2024–2025 — GPT-5.5 100%, GPT-6 Astra 100%; SimpleQA Verified — GPT-6 Astra 75.6%, GPT-5.5 63.0%.

Which is better for coding?

There are no published SWE-bench Verified results for GPT-6 Astra yet, so there is no like-for-like coding score. On overall capability, GPT-6 Astra leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

GPT-5.5 and GPT-6 Astra share the same 1,050,000-token context window. Maximum output per response: GPT-5.5 up to 128,000, GPT-6 Astra up to 128,000 tokens.

Which can read images, PDFs, audio or video?

GPT-5.5 accepts text, images and PDFs; GPT-6 Astra accepts text, images and PDFs. They handle the same number of input types.

Are any of these open source?

No. GPT-5.5 and GPT-6 Astra are proprietary and only available through APIs and apps.

Which is newer?

GPT-6 Astra is the newest, released Sep 4, 2026. GPT-5.5 came out Apr 23, 2026. Knowledge cutoff: GPT-5.5 Dec 1, 2025, GPT-6 Astra Apr 30, 2026.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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