As of August 20, 2026, Grok 4.5 is 49% cheaper per million tokens than GPT-5.3 Chat. GPT-5.3 Chat is $1.75 / $14.00 per million input/output tokens versus Grok 4.5 at $2.00 / $6.00. Sources: https://developers.openai.com/api/docs/pricing and https://docs.x.ai/docs/models
Sources: OpenAI API pricing (https://developers.openai.com/api/docs/pricing); xAI API pricing (https://docs.x.ai/docs/models)
GPT-5.3 Chat
OpenAI
Input
$1.75
Output
$14.00
Grok 4.5
xAI
Input
$2.00
Output
$6.00
Token pricing, specs, and benchmarks side by side
GPT-5.3 ChatGrok 4.5Verdict
Both models are closely matched on benchmarks. Grok 4.5 has the pricing advantage, making it the better value unless GPT-5.3 Chat's specific capabilities are critical to your workflow.
As of August 20, 2026, Grok 4.5 is 49% cheaper on blended LLM API pricing. Grok 4.5 costs $2.00 per million input tokens and $6.00 per million output tokens ($8.00 blended 1M-in + 1M-out). GPT-5.3 Chat costs $1.75 / $14.00 per million tokens ($15.75 blended). Sources: https://developers.openai.com/api/docs/pricing and https://docs.x.ai/docs/models. The cheapest LLM for your app still depends on how many output tokens you generate.
GPT-5.3 Chat OpenAI API pricing is $1.75 input and $14.00 output per million tokens via OpenAI. Grok 4.5 xAI API pricing is $2.00 input and $6.00 output per million tokens via xAI. Use those four numbers, not ChatGPT Plus or Claude Pro subscription prices, when you are comparing APIs.
Grok 4.5 has a published SWE-bench Verified score of 86.6%. GPT-5.3 Chat does not have that eval on this page yet.
GPT-5.3 Chat supports a 128K token context window, while Grok 4.5 supports 500K tokens. Grok 4.5 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.
Shared benchmark scores for GPT-5.3 Chat and Grok 4.5 are still limited. Check the comparison table for the evals each model has published. 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.
Both GPT-5.3 Chat and Grok 4.5 are production API models. For cost-sensitive production traffic, Grok 4.5 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.
Yes. Call GPT-5.3 Chat through OpenAI and Grok 4.5 through xAI 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.
List rates are the latest published OpenAI API pricing and xAI API pricing, quoted per million tokens. Official rate sheets: https://developers.openai.com/api/docs/pricing and https://docs.x.ai/docs/models. 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.
GPT-5.3 Chat supports up to 16K output tokens per request, while Grok 4.5 supports up to an unspecified number of output tokens. Output tokens are usually the expensive half of API pricing, so a higher max output cap is a capability, not a discount.
GPT-5.3 Chat runs at approximately 100 tokens/second while Grok 4.5 runs at 80 tokens/second. GPT-5.3 Chat 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.
Use the model pickers at the top of this LLM comparison. Search any model in the index and the URL updates. Open GPT-5.3 Chat or Grok 4.5 from the sidebar for the single-model API pricing page, or go back to the LLM pricing table to sort by cheapest blended cost.
This comparison covers API pricing, context window, throughput, and benchmark scores. GPT-5.3 Chat costs $1.75/M input and $14.00/M output. Grok 4.5 costs $2.00/M input and $6.00/M output.
Rank both on the LLM leaderboard, SWE-bench, and Humanity's Last Exam.
The index
280 models across 33 providers. Search or jump to a lab — every model page stays linked here.
Next step
Auth, billing, and the API layer are already decided. Fork 8 finished AI apps, or have us build the first version with you.
