GPT-5.1 vs Grok 4.3
OpenAI against xAI, costed on the same three workloads. Grok 4.3 is cheaper on all three workloads.
Run this comparison on your own numbers
Monthly bill, side by side
| Workload | GPT-5.1 | Grok 4.3 | Difference |
|---|---|---|---|
| Support chatbot 2,500 six-turn conversations a day |
$6,553 | $3,516 | $3,038 (1.9×) |
| Document summarizer 1,000 single-shot summaries a day |
$698 | $518 | $180 (+35%) |
| Coding agent 200 twelve-turn sessions a day |
$4,185 | $2,835 | $1,350 (+48%) |
No prompt caching and no batch discount on either side, so the comparison is like for like. Both figures assume 30 days a month.
The rate cards
| GPT-5.1 | Grok 4.3 | |
|---|---|---|
| Input, per 1M tokens | $1.25 | $1.25 |
| Output, per 1M tokens | $10 | $2.5 |
| Cached input | $0.125 | $0.2 |
| Context window | 272K | 1M |
| Maximum output | 128K | 1M |
| Reasoning model | yes | yes |
| Vision | yes | yes |
Beyond the price
- Grok 4.3 reads up to 1M tokens of context in one request; GPT-5.1 stops at 272K.
- Grok 4.3 can write up to 1M tokens in one response, against 128K for GPT-5.1.
- Cached input costs 90% less than fresh input on GPT-5.1 and 84% less on Grok 4.3, which matters most for workloads that resend the same prompt.
Run this comparison on your own numbers
Full detail: GPT-5.1 pricing · Grok 4.3 pricing
More comparisons
Other head-to-heads that include GPT-5.1 or Grok 4.3.
- GPT-5.1 vs Nova 2 Pro
- GPT-5.1 vs GLM-5
- GPT-5.1 vs GLM-5.1
- Grok 4.3 vs Nova 2 Pro
- Grok 4.3 vs Claude Haiku 4.5
- Grok 4.3 vs DeepSeek V4 Pro
Common questions
Which is cheaper, GPT-5.1 or Grok 4.3?
Grok 4.3 is cheaper on all three workloads.
How much would GPT-5.1 and Grok 4.3 cost each month?
On PromptSpend's standard workloads, per month: support chatbot: GPT-5.1 $6,553, Grok 4.3 $3,516 (Grok 4.3 is cheaper by $3,038); document summarizer: GPT-5.1 $698, Grok 4.3 $518 (Grok 4.3 is cheaper by $180); coding agent: GPT-5.1 $4,185, Grok 4.3 $2,835 (Grok 4.3 is cheaper by $1,350). No prompt caching and no batch discount is assumed.
How do GPT-5.1 and Grok 4.3 differ apart from price?
Grok 4.3 reads up to 1M tokens of context in one request; GPT-5.1 stops at 272K. Grok 4.3 can write up to 1M tokens in one response, against 128K for GPT-5.1. Cached input costs 90% less than fresh input on GPT-5.1 and 84% less on Grok 4.3, which matters most for workloads that resend the same prompt.