GPT-6.1 Sol vs GPT-6 Astra: Price, Limits and Which to Use

GPT-6.1 Sol vs GPT-6 Astra is a choice between OpenAI's most capable GPT-6 model and a lower-priced model it describes as near-Astra. OpenAI calls Astra "our most capable model for the most demanding work" and describes GPT-6.1 Sol as "near-Astra performance for complex work at a lower cost"^[1][2]. On paper the two share the same context window, output ceiling and knowledge cutoff. On price they are far apart: Sol costs one fifth of Astra per input and output token.

This comparison uses OpenAI's documentation, retrieved October 28, 2026: both model pages, the GPT-6 guide, the pricing page and the changelog. It covers what each model is for, what the price gap means per request, where GPT-6 Sol and GPT-5.6 Sol fit, and what changes when you call them through reAPI. It does not use benchmark scores; no independent evaluation was reviewed for this article.

TL;DR

• Positioning: Astra is OpenAI's most capable model; GPT-6.1 Sol targets "complex coding, computer use, and professional work" at near-Astra level^[1][2].
• Price: Sol is $2.00 input and $10.00 output per 1M tokens; Astra is $10.00 and $50.00. Cached input is $0.10 vs $1.00^[3].
• Limits: identical 1,050,000-token context, 128,000 output tokens and April 30, 2026 knowledge cutoff^[1][2].
• Reasoning: both list low to max and neither supports none^[4].
• Per task: OpenAI says Astra used substantially fewer output tokens than earlier models in several evaluations, so the per-task gap can be smaller than the per-token gap^[4].
• Rule of thumb (our judgment): default to GPT-6.1 Sol, and move a task to Astra when Sol's answers fall short and the task is worth up to five times the input and output token price.

GPT-6.1 Sol vs GPT-6 Astra in one table

Sources: OpenAI model pages, changelog and pricing^[1][2][3][5].

Price and positioning are the main practical differences; the two were released 26 days apart. Everything a developer usually checks first, from context size to modalities and cutoff, is the same. Both models also support Chat Completions, but OpenAI's guide is explicit that "tool calling requires Responses" for GPT-6 Astra and GPT-6.1 Sol^[4].

What the price gap means per request

At OpenAI's Standard rates, GPT-6.1 Sol costs one fifth of Astra on input and output, and one tenth on cached input^[3]. Above 272K input tokens both move to long-context rates: $4.00 / $0.20 / $15.00 for Sol and $20.00 / $2.00 / $75.00 for Astra^[3].

Arithmetic per 1M tokens at Standard: for the cached row, Sol is 2,000 × $2 + 18,000 × $0.10 + 800 × $10 and Astra is 2,000 × $10 + 18,000 × $1 + 800 × $50^[3].

Per-token price is not the whole story. OpenAI's guide says that in several evaluations "Astra achieved stronger results using substantially fewer output tokens", and that "its estimated API cost per task was lower than earlier models despite its higher per-token pricing"^[4]. That comparison is against earlier models, not against GPT-6.1 Sol, and the OpenAI documentation reviewed here gives no Sol-to-Astra token ratio. Our arithmetic: on an output-heavy task, Astra only costs less than Sol if it needs under one fifth of Sol's output tokens for the same answer. Measure that on your own tasks before assuming either way.

Reasoning effort and speed tiers

Both models accept low, medium, high, xhigh and max; OpenAI's guide notes that "GPT-6 Astra and GPT-6.1 Sol do not support the none reasoning effort"^[4]. Reasoning tokens bill as output: at OpenAI's Standard rates each reasoning token costs five times as much on Astra, and the total depends on how many tokens each model uses.

Both also have faster, pricier tiers. Fast mode is 2× Standard and Ultrafast 6× Standard for GPT-6.1 Sol^[1]. In the pricing tables, Sol Ultrafast is $12.00 input and $60.00 output per 1M tokens, while Astra Ultrafast is $60.00 and $300.00^[3]. Data residency differs too: "Ultrafast mode for GPT-6.1 Sol supports US and EU data residency and global processing. GPT-6 Astra Ultrafast supports US data residency and global processing only"^[4].

Where GPT-6 Sol and GPT-5.6 Sol fit

GPT-6.1 Sol arrived one week after GPT-6 Sol shipped on September 22, 2026; OpenAI's GPT-6 Sol page now points to "the newer Sol model"^[5][6].

Sources: OpenAI pricing and model pages^[3][1][2][6].

Moving from GPT-6 Sol to GPT-6.1 Sol keeps input and output prices and halves cached input. Two behaviors change: GPT-6 Sol supports none effort and allows function calling in Chat Completions with reasoning_effort: "none", while GPT-6.1 Sol has no none level and needs the Responses API for tools^[6][4]. If your Chat Completions code relies on tools at none, test before switching. GPT-5.6 Sol cost twice GPT-6.1 Sol for input and output^[3].

GPT-6.1 Sol and GPT-6 Astra on reAPI

Both models are on reAPI's Chat Completions endpoint, billed per token from one credit balance. On October 28, 2026 the reAPI rates per 1M tokens were $2.00 input, $0.10 cached input and $10.00 output for GPT-6.1 Sol, and $8.00, $0.80 and $40.00 for GPT-6 Astra^[7][8]. On reAPI the gap is therefore four times on input and output, not five, because Astra is billed below OpenAI's list price there and Sol at it.

One difference is specific to this endpoint. In reAPI's checks on October 28, 2026, GPT-6.1 Sol accepted low to xhigh, and reasoning_effort: "max" returned an error, uncharged^[9]. reAPI's GPT-6 Astra docs list low to max as accepted^[10]. If your workload needs Sol at max, use xhigh on reAPI or compare against Astra at max. Both endpoints use the same key, so running the same prompts through each is a model-id change.

FAQ

is gpt 6.1 sol better than astra

OpenAI's documentation does not say so. It positions GPT-6 Astra as its most capable model and GPT-6.1 Sol as near-Astra performance at a lower cost^[1][2]. Official specifications do not measure quality on your tasks; run the same prompts through both before choosing.

gpt 6.1 sol price vs astra

At OpenAI's Standard rates, GPT-6.1 Sol costs $2.00 input, $0.10 cached input and $10.00 output per 1M tokens; GPT-6 Astra costs $10.00, $1.00 and $50.00^[3]. That is one fifth for input and output and one tenth for cached input.

gpt 6.1 sol vs gpt 6 sol

Same input and output price, half the cached-input rate, a knowledge cutoff ten days later, and no none effort level^[1][6]. GPT-6 Sol allows function calling in Chat Completions at none; GPT-6.1 Sol needs the Responses API for tools^[4].

gpt 6.1 sol vs 5.6 sol

GPT-6.1 Sol costs half of GPT-5.6 Sol for input and output, $2.00 vs $4.00 and $10.00 vs $20.00 per 1M tokens, and a quarter for cached input, $0.10 vs $0.40^[3].

gpt 6.1 sol high vs astra

The OpenAI documentation reviewed here does not compare Sol at high with Astra at a given effort, so quality is a question for your own tests. On cost, every reasoning token Sol spends at high bills at $10 per 1M output tokens, against $50 on Astra^[3].

gpt 6.1 sol ultra vs astra

Sol Ultrafast costs $12.00 input and $60.00 output per 1M tokens; Astra Ultrafast costs $60.00 and $300.00^[3]. Sol Ultrafast supports US and EU data residency; Astra Ultrafast supports US data residency only, plus global processing for both^[4].

Picking between GPT-6.1 Sol and GPT-6 Astra

Start with GPT-6.1 Sol for coding, analysis and document work: same limits, same cutoff, a fifth of the input and output price and a tenth of the cached-input price at OpenAI. Keep a small set of hard tasks from your own workload, run them through both models at the same effort, and move only the tasks where Astra's answers are clearly better, or where it uses enough fewer tokens to close the price gap. That makes GPT-6.1 Sol vs GPT-6 Astra a per-task routing decision rather than a single switch. Current rates and a playground for each are on the GPT-6.1 Sol and GPT-6 Astra model pages.

References

1. OpenAI. GPT-6.1 Sol model page. Retrieved October 2026 from developers.openai.com/api/docs/models/gpt-6.1-sol
2. OpenAI. GPT-6 Astra model page. Retrieved October 2026 from developers.openai.com/api/docs/models/gpt-6-astra
3. OpenAI. API pricing. Retrieved October 2026 from developers.openai.com/api/docs/pricing
4. OpenAI. GPT-6 guide. Retrieved October 2026 from developers.openai.com/api/docs/guides/latest-model
5. OpenAI. API changelog, September 3, 22 and 29, 2026. Retrieved October 2026 from developers.openai.com/api/docs/changelog
6. OpenAI. GPT-6 Sol model page. Retrieved October 2026 from developers.openai.com/api/docs/models/gpt-6-sol
7. reAPI. GPT-6.1 Sol model page. Retrieved October 2026 from reapi.ai/models/gpt-6-1-sol
8. reAPI. GPT-6 Astra model page. Retrieved October 2026 from reapi.ai/models/gpt-6-astra
9. reAPI. GPT-6.1 Sol API docs. Retrieved October 2026 from reapi.ai/docs/gpt-6-1-sol
10. reAPI. GPT-6 Astra API docs. Retrieved October 2026 from reapi.ai/docs/gpt-6-astra