// head_to_head
GPT-5.1 vs SpaceXAI: Grok 4.5
Published LiveBench scores across all seven categories, live list pricing, context windows, and the measured cost of a point of capability — for both models, side by side.
SpaceXAI: Grok 4.5 is the cheaper of the two; neither can be ranked on quality here.
GPT-5.1 does not have a published LiveBench run, so this comparison covers price, context and declared capabilities only. A missing score means "not evaluated", not "worse" — the right way to separate these two is an eval on your own workload.
openai
GPT-5.1
- Blended / 1M
- $3.44
- Context
- 400K
- Released
- Nov 13, 2025
- Overall score
- Not evaluated
x-ai
SpaceXAI: Grok 4.5
- Blended / 1M
- $3.00
- Context
- 500K
- Released
- Jul 8, 2026
- Overall score
- 75.8
Specs and pricing
| Metric | GPT-5.1 | SpaceXAI: Grok 4.5 |
|---|---|---|
| LiveBench overall Mean of the seven LiveBench category scores, 0–100. Higher is better. | — | 75.8 |
| Cost per point Measured benchmark spend divided by overall score — dollars per point of capability. | — | $0.0720 |
| Blended price / 1M 3:1 input:output mix, the usual shape of production traffic. | $3.44 | $3.00win |
| Input price / 1M | $1.25win | $2.00 |
| Output price / 1M | $10.00 | $6.00win |
| Cached input / 1M Price of an input token served from the prompt cache, where the provider publishes one. | $0.125win | $0.300 |
| Context window | 400K | 500K |
| Max output tokens | 128K | 450Kwin |
Benchmarks by category
An overall score averages away the thing you probably care about. These are the seven LiveBench categories scored separately — GPT-5.1 on top, SpaceXAI: Grok 4.5 below, both out of 100.
What each one costs to run
Per-token prices are hard to feel. These are monthly list costs for both models across five workload shapes, using each provider's published cached-input rate where there is one.
| Workload | GPT-5.1 | SpaceXAI: Grok 4.5 |
|---|---|---|
| Support chatbot 1.2K in / 400 out × 200K requests | $1,019/mo | $837.60/mo |
| RAG assistant 8K in / 600 out × 100K requests | $1,150/mo | $1,280/mo |
| Coding agent 40K in / 4K out × 20K requests | $1,170/mo | $1,128/mo |
| Document extraction 20K in / 1.5K out × 50K requests | $1,944/mo | $2,365/mo |
| Bulk classification 500 in / 20 out × 5M requests | $3,563/mo | $4,750/mo |
Which should you pick?
You are cost-constrained
SpaceXAI: Grok 4.5
Cheaper on blended list price at $3.00 per million tokens.
GPT-5.1 vs SpaceXAI: Grok 4.5 FAQ
Which is better, GPT-5.1 or SpaceXAI: Grok 4.5?
SpaceXAI: Grok 4.5 is the cheaper of the two; neither can be ranked on quality here. GPT-5.1 does not have a published LiveBench run, so this comparison covers price, context and declared capabilities only. A missing score means "not evaluated", not "worse" — the right way to separate these two is an eval on your own workload.
Is GPT-5.1 cheaper than SpaceXAI: Grok 4.5?
SpaceXAI: Grok 4.5 is cheaper. On a 3:1 input:output blend, GPT-5.1 lists at $3.44 per million tokens and SpaceXAI: Grok 4.5 at $3.00 — SpaceXAI: Grok 4.5 is 15% cheaper. Input and output are priced separately — GPT-5.1 charges $1.25 in and $10.00 out, SpaceXAI: Grok 4.5 charges $2.00 and $6.00 — so the model that looks cheaper flips depending on how output-heavy your workload is.
Does GPT-5.1 or SpaceXAI: Grok 4.5 have a bigger context window?
They are effectively the same — 400K for GPT-5.1 and 500K for SpaceXAI: Grok 4.5.
Do GPT-5.1 and SpaceXAI: Grok 4.5 support prompt caching?
Both publish a cached-input rate: $0.125 per million for GPT-5.1 and $0.300 for SpaceXAI: Grok 4.5, against full input rates of $1.25 and $2.00. On a workload with a long stable prefix — a system prompt, a tool schema, a retrieved corpus — that changes the economics more than the headline price does.
Related comparisons
How these numbers are produced
- Price — provider list price from OpenRouter, refreshed every 15 minutes. “Blended” is a 3:1 input:output mix.
- Scores — LiveBench release 2026-06-25, using their own category map. Each model shows its strongest published run. A blank means “not evaluated”, never “bad”.
- Cost per point — the measured dollars LiveBench spent on the run, divided by the score it earned.
- “Win” — awarded only past a threshold: one full point on a benchmark score, 10% on a price, 25% on a context window. Anything tighter reports as a tie, because effort settings alone move a LiveBench score by more than that.
Published benchmarks rank models on someone else's tasks. Before committing, see LLM & agent evaluation for building an eval on your own.