Which is cheaper, GPT-5.1 Instant or Mercury 2?
As of August 25, 2026, Mercury 2 is 91% cheaper on blended LLM API pricing. Mercury 2 costs $0.25 per million input tokens and $0.75 per million output tokens ($1.00 blended 1M-in + 1M-out). GPT-5.1 Instant costs $1.25 / $10.00 per million tokens ($11.25 blended). Sources: https://developers.openai.com/api/docs/pricing and https://anotherwrapper.com/tools/llm-pricing. The cheapest LLM for your app still depends on how many output tokens you generate.
How much does GPT-5.1 Instant vs Mercury 2 cost per million tokens?
GPT-5.1 Instant OpenAI API pricing is $1.25 input and $10.00 output per million tokens via OpenAI. Mercury 2 Inception API pricing is $0.25 input and $0.75 output per million tokens via Inception. Use those four numbers, not ChatGPT Plus or Claude Pro subscription prices, when you are comparing APIs.
Which is better for coding, GPT-5.1 Instant or Mercury 2?
GPT-5.1 Instant has a published SWE-bench Verified score of 76.3%. Mercury 2 does not have that eval on this page yet.
What is the context window for GPT-5.1 Instant vs Mercury 2?
GPT-5.1 Instant supports a 400K token context window, while Mercury 2 supports 128K tokens. GPT-5.1 Instant offers a larger context window. Filling a larger window bills more input tokens, so the cheaper-per-million model can still cost more on long documents.
Which model performs better on benchmarks, GPT-5.1 Instant or Mercury 2?
GPT-5.1 Instant leads on 3 of 3 shared benchmarks versus Mercury 2's 0 wins. Check the comparison table for GPQA Diamond, SWE-bench, MMLU, HLE, and the other evals we track. Token price and benchmark score together are the usual LLM comparison, not either number alone.
Is GPT-5.1 Instant or Mercury 2 better for production use?
Both GPT-5.1 Instant and Mercury 2 are production API models. For cost-sensitive production traffic, Mercury 2 has better economics on the blended 1M-in + 1M-out scale. For maximum capability, weight the benchmark table for your domain. Many production stacks route cheap models for drafts and a frontier model for the hard turn, which is usually cheaper than sending everything to the expensive API.
Can I switch between GPT-5.1 Instant and Mercury 2 in my app?
Yes. Call GPT-5.1 Instant through OpenAI and Mercury 2 through Inception with separate API keys, or through a gateway that already wraps both. Keep prompts in tokens, not characters, when you estimate the invoice. AnotherWrapper templates can swap providers without rewriting auth and billing.
How accurate is this GPT-5.1 Instant vs Mercury 2 pricing data?
List rates are the latest published OpenAI API pricing and Inception API pricing, quoted per million tokens. Official rate sheets: https://developers.openai.com/api/docs/pricing and https://anotherwrapper.com/tools/llm-pricing. Prompt caching, batch APIs, and committed-use discounts can change the invoice. Benchmark scores are from official publications and independent evals, updated as new numbers land.
What is the output token limit for GPT-5.1 Instant and Mercury 2?
GPT-5.1 Instant supports up to 128K output tokens per request, while Mercury 2 supports up to 8K output tokens. Output tokens are usually the expensive half of API pricing, so a higher max output cap is a capability, not a discount.
Which model has better throughput, GPT-5.1 Instant or Mercury 2?
GPT-5.1 Instant runs at approximately 100 tokens/second while Mercury 2 runs at 1009 tokens/second. Mercury 2 is faster in raw throughput. Throughput (tokens per second) and time-to-first-token are why two models with the same per-million-token price can still feel different in chat and agents.
How do I switch the models in this GPT-5.1 Instant vs Mercury 2 comparison?
Use the model pickers at the top of this LLM comparison. Search any model in the index and the URL updates. Open GPT-5.1 Instant or Mercury 2 from the sidebar for the single-model API pricing page, or go back to the LLM pricing table to sort by cheapest blended cost.
