GPT-6 Astra vs Claude Opus 5.5
Official OpenAI and Anthropic API prices and LMArena scores, checked 2026-10-29. Add up to 2 more models to compare 4.
Claude Opus 5.5 is cheaper and wins more LMArena tasks.
Claude Opus 5.5 is 2.5x cheaper on input and output. Claude Opus 5.5 scores 94 points higher for creative writing. Across 7 shared LMArena tasks, Claude Opus 5.5 leads 7 to 0. A medium month (20M input + 5M output tokens) costs $450 on GPT-6 Astra and $180 on Claude Opus 5.5.
- Pick GPT-6 Astra if nothing here clearly favors it (no lower bill, bigger context, cheaper cache or LMArena lead of 3+ points over Claude Opus 5.5).
- Pick Claude Opus 5.5 if you want the lower bill ($180 vs $450 for a medium month), you care most about creative writing (+94), chat (+62) and reasoning and math (+39) or you reuse long prompts (cached input $0.20 vs $1).
Medium: 20M input + 5M output tokens a month at list price (short-context rate, no caching or batch discounts).
Marked side is better: lower for prices, higher for context and scores. Bars are scaled to the larger of the two.
| Spec | GPT-6 Astra | Claude Opus 5.5 |
|---|---|---|
| Price per 1M tokens | ||
| Input | $10 | $4 |
| Cached input | $1 | $0.20 |
| Output | $50 | $20 |
| Blend 3:1 | $20 | $8 |
| Sample month, medium | $450 | $180 |
| Context | ||
| Context window | 1.05M tokens | 1M tokens |
| Quality (LMArena, out of 100) | ||
| Coding | 87/100 #2 of 50 | 100/100 #1 of 50 |
| Chat | 16/100 #19 of 51 | 78/100 #2 of 51 |
| Creative writing | 6/100 #17 of 51 | 100/100 #1 of 51 |
| Roleplay and characters | 13/100 #13 of 51 | 37/100 #5 of 51 |
| Reasoning and math | 25/100 #18 of 51 | 64/100 #5 of 51 |
| Vision | 66/100 #10 of 33 | 84/100 #3 of 33 |
| Long documents | 78/100 #6 of 11 | Not ranked |
| Cheap bulk and agents | 79/100 #4 of 34 | 100/100 #1 of 34 |
| Details | ||
| Provider | OpenAI | Anthropic |
| API model id | gpt-6-astra | claude-opus-5.5 |
| Notes | Prompts up to 272K. Longer prompts cost $20 in, $75 out. | 5-minute cache writes $5. |
| Sources | ||
| Last checked | 2026-10-29 | 2026-10-29 |
| Official pricing | OpenAI pricing | Anthropic pricing |
Plans from data checked hourly against each vendor's official pricing page. Vendors state limits in different units, so we quote them as published. Team and enterprise plans are per seat.
API prices in USD per 1M tokens from each provider's official pricing page. Blend 3:1 = (3 x input + output) / 4. Sample month = stated input and output tokens at the list price, no caching. Quality: relative score out of 100 on each LMArena leaderboard (100 = top model we price on that board, n/a = not ranked there), data licensed CC BY 4.0. See how we pick.
Where each one ranks on LMArena
Relative score out of 100 on each leaderboard (100 = the top model we price there), with the rank among the models from our API price table that appear on that board.
- Coding (Code Arena): GPT-6 Astra #2 of 50 (87/100), Claude Opus 5.5 #1 of 50 (100/100)
- Chat (Text Arena): GPT-6 Astra #19 of 51 (16/100), Claude Opus 5.5 #2 of 51 (78/100)
- Creative writing (Text Arena creative writing): GPT-6 Astra #17 of 51 (6/100), Claude Opus 5.5 #1 of 51 (100/100)
- Roleplay and characters (Text Arena multi-turn): GPT-6 Astra #13 of 51 (13/100), Claude Opus 5.5 #5 of 51 (37/100)
- Reasoning and math (Text Arena math): GPT-6 Astra #18 of 51 (25/100), Claude Opus 5.5 #5 of 51 (64/100)
- Vision (Vision Arena): GPT-6 Astra #10 of 33 (66/100), Claude Opus 5.5 #3 of 33 (84/100)
- Long documents (Document Arena): GPT-6 Astra #6 of 11 (78/100), Claude Opus 5.5 not ranked
- Cheap bulk and agents (Agent Arena): GPT-6 Astra #4 of 34 (79/100), Claude Opus 5.5 #1 of 34 (100/100)
Pricing details from the official pages
GPT-6 Astra lists $10 input, $50 output, $1 cached input per 1M tokens on OpenAI pricing. Claude Opus 5.5 lists $4 input, $20 output, $0.20 cached input per 1M tokens on Anthropic pricing. Prices checked 2026-10-29.
- GPT-6 Astra: Prompts up to 272K. Longer prompts cost $20 in, $75 out.
- Claude Opus 5.5: 5-minute cache writes $5.
Sample monthly bill at list price, no caching: Light (2M input + 0.5M output tokens): $45 vs $18. Medium (20M input + 5M output tokens): $450 vs $180. Heavy (200M input + 50M output tokens): $4,500 vs $1,800.
FAQ
Is GPT-6 Astra cheaper than Claude Opus 5.5?
GPT-6 Astra costs $10 input and $50 output per 1M tokens; Claude Opus 5.5 costs $4 and $20. For a medium month (20M input + 5M output tokens) Claude Opus 5.5 is cheaper: $180 vs $450.
Which is better for coding, GPT-6 Astra or Claude Opus 5.5?
On LMArena's Code Arena GPT-6 Astra scores 87/100 (#2 of 50) and Claude Opus 5.5 100/100 (#1 of 50), so Claude Opus 5.5 is ahead by 13 points.
Which has the bigger context window?
GPT-6 Astra: 1.05M tokens. Claude Opus 5.5: 1M tokens. Long prompts can cost more; see the pricing notes above.
How much do GPT-6 Astra and Claude Opus 5.5 cost per month?
Light (2M input + 0.5M output tokens): $45 vs $18. Medium (20M input + 5M output tokens): $450 vs $180. Heavy (200M input + 50M output tokens): $4,500 vs $1,800. Pick your own token counts in the plan vs API calculator.
Where do these numbers come from?
Prices come from each provider's official pricing page, checked daily. Quality is the relative score on the LMArena leaderboard dataset, licensed CC BY 4.0. Where a model is not ranked we show n/a.
Sources
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